acceleration

If it comes back to you, it's yours!

esiegel — Mon, 10 Sep 2012 15:49:35 +0000

If it comes back to you, it's yours!

"Not even light can escape such hollowing, this huge mass in a small space. Even the Milky Way with its open arms is said to have a black hole at its heart." -Susan B.A. Somers-Willett

Our Milky Way is home to us all. With its hundreds of billions of stars, massive spiral arms, dust lanes, and orbiting globular clusters, it's no wonder that nearly everything we see in the night sky is contained within it.

I say nearly everything, of course, because there are a few exceptions. The Andromeda Galaxy, for one, as well as the two Magellanic Clouds, for another. It was less than 100 years ago that we realized that the vast majority of those "faint fuzzies" in the night sky -- nebulous structures that came in spiral, elliptical, and irregular shapes -- were actually galaxies unto themselves.

Image credit: Hubble Legacy Archive, ESA, NASA; Processing credit: Al Kelly.

They range in size from hundredths to hundreds of times the mass of our own Milky Way, but the one thing that almost all of them have in common with one another is that they're rapidly receding away from us.

Image credit: the Astrophysics Research Institute at Liverpool John Moores University.

The observation that, in general, the farther away a galaxy is from us, the faster it's moving away from us (and not other interpretations) led us to conclude that the Universe is expanding. While gravitation is working to slow the expansion and attract all massive objects towards one another, the initial expansion was extremely powerful. As a result, it isn't everywhere and in all cases that gravitation wins.

Image credit: Rogelio Bernal Andreo of http://www.deepskycolors.com/.

Sure, in some locations -- like the Virgo Cluster, above -- thousands of large galaxies become gravitationally bound to one another. There are many great clusters where this is the case, and they are the major causes of deviations and imperfections in the general expansion of the Universe. In locations where great concentrations of mass are vitally important, these galaxies will achieve some maximum, finite distance between them, and wind up eventually moving back towards one another and merging far into the future.

Image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech).

While this is the fate of many of the galaxies visible in our night sky -- to merge with some of the largest clusters in the Universe -- that is not the fate of the Milky Way. Not to merge with the Virgo Cluster, nor with any other large group of galaxies. In fact, thanks to the presence and dominance of dark energy, it is a certainty that only the galaxies that are today moving towards us have a chance of someday merging with us; all the others will eventually expand away, towards infinity, into the abyss of deep space.

Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team.

Want to know who will wind up coming back to us in the future?

Image credit: NASA, nasaimages.org, SDSS, Atlas of the Universe and R. Harris.

There's everyone presently in our local group, which includes our bigger sister, Andromeda, as well as -- in order of decreasing size -- M33, the Large Magellanic Cloud, the Small Magellanic Cloud, M32, NGC 205, NGC 6822, NGC 185, IC 1613 and NGC 147. They're all going to merge with us, and they're all going to undergo rapid bursts of star formation when one of the other local-group members gets close enough to gravitationally induce star formation.

In other words, everyone in the local group has fireworks in their future. Everyone, that is, except the dwarf galaxy IC 10, which has fireworks right now.

Image credit: Dietmar Hager, Torsten Grossmann.

The closest (at just 2.3 million light years distant) known starburst galaxy -- a galaxy that's forming stars so rapidly the entire galaxy has become a star-forming region -- and the only starburst galaxy within the local group, this burst of star formation awaits each member of the local group in the future, as we will all eventually merge into a single, giant elliptical.

All of these -- plus the other, even smaller members of our local group -- will eventually merge together. Even the ones that are moving (slightly) away from us at the moment won't be for long, as they will come back to us under the intense pull of eveyone's combined gravity. That's our fate, but there's one more possibility: someone who will probably not be joining us, but may, if things work out right.

Image credit: Graeme Coates of http://www.chromosphere.co.uk/.

The giant spiral galaxy, M81, is shown above with its starbursting (and smaller) companion, M82. M81 is the largest galaxy in its local group of 34 small objects, and is well outside our local group at a distance of nearly 12 million light years.

However!

M81 is moving towards us, ever so slightly, at a speed of about 1 km/s. Does that mean it will merge with us, overcoming the Hubble expansion of the Universe, and leading to a great galactic pileup?

Image credit: Subaru Telescope and NAOJ.

Unlikely! While M81 is moving towards us ever-so-slightly, M82 is moving rapidly away from us (about 200 times as quickly as M81 moves towards us), and both M81 and M82 are bound, gravitationally, to one another.

This very likely means that the motion of M81 towards us is ephemeral, and that it will wind up merging with M82, and the combined, post-merger galaxy will continue to expand away from us, into the great and distant void. Still, there's much more to learn before we can say with absolute certainty that this is the case.

We've got no choice but to let go of these and all the other distant galaxies in the Universe. If they come back to us, they'll be ours forever, but if not, don't despair; they have their own futures to write!

esiegel Mon, 09/10/2012 - 11:49

Tags

Big Bang

Galaxies

gravity

Physics

It's sad to thing that in a few trllions years, living beings will look up and see mostly black, as all the other galaxies have moved beyond their ability to see.

@Chris Sheep, in about a trillion years, its not going to be all blackness. After most of the local clusters merging into one, its going to be a very beautiful looking Single galaxy.

But where will we humans be looking from, how would have we evolved over a trillion years, or will we even exist.

If globally seen, there is an ongoing activity of Galaxy's that are close to each other and that are being pulled towards each other, while some do escape, than how can they all be globally moving away from each other? How can the balloon be expanding when all the coins are staying relatively in place?

... and additionally how do you know where a 'cluster' starts and end if you look at this picture with stellar networks from Boylan-Kolchin et al. on the 'Says something smart' post: http://scienceblogs.com/startswithabang/files/2012/08/millennium2zoom_p…

Galaxies, chelle.

Apostrophe denotes missing letters or possessive.

VDGG,

One thing is pretty certain. We won't be looking up from earth in a trillion years. The sun should become a red giant and either completely swallow the earth or cause it to become utterly lifeless a LONG time before a trillion years from now, at least 990 billion or so years according to theories of stellar development.

Welcom back from your vacation, Ethan! Hope it was very enjoyable!

How can the balloon be expanding when all the coins are staying relatively in place?

There are two forces at play; gravity and the expansion. For larger masses and closer objects, gravity wins.

Your question is like asking 'if gravity, how can the atoms on the top of my head not fall to the bottom of my feet?" Answer: because there is another force at play, and that force is locally stronger.

Speaking of light -If you are familiar with the work of using solar sails to accelerate space payloads, it might be appropriate to forward this song by Swedish band Agnes - "Into the Sun" http://soundcloud.com/joaopavao/agnes-into-the-sun :-)

"For larger masses and closer objects, gravity wins."

Well that is exactly my point, if gravity between the coins on the balloon wins in 30% of the cases let's say, than how can the balloon/universe be equally expanding, certainly when you look at that image with all the canals. If so, than isn't gravity countering the expansion, holding everything together like a chain made out of gravity links, it is doing so at least in our 'section', and who says that other sections are so much different than ours, and one 'section' or 'group of clusters' is entangled with the one next to it ... and how do you even define a section when it all flows through each other?

tl;dr and your post might have covered this, but you are wrong when you say that "these galaxies will achieve some maximum, finite distance between them, and wind up eventually moving back towards one another and merging far into the future." How did you come to this conclusion?
Aren't the galaxies in fact ACCELERATING away from us due to the expansion of space-time?
Gravity is NOT winning this one.

lash, if it's TLDR and you already admit the post may have covered it, in what sense do you think anyone will bother to answer your question?

You've already said you haven't read if there was one already.

lash, read and learn instead of attempting to guess and teach... #facepalm

@ Chelle "How can the balloon be expanding when all the coins are staying relatively in place?"

Surely things would stay "relatively in place" if the expansion was the same everywhere. All distances would simply increase in proportion. Local differences in the rate of expansion (however caused) would change the local distribution of mass, and objects attracted by gravity can move towards each other against the the local expansion of the balloon, and one effect will ultimately dominate. Just like walking up a down escalator, where there will be a boundary condition: on one side you will eventually end up at the top, and on the other you will eventually end up at the bottom

DavidL,

"Local differences in the rate of expansion ... would change the local distribution of mass"

Yes, but here I come back to my previous question (September 11, 1:38 pm), what defines our 'section' or what is 'local' as you put it? For instance if you have this row of stars going from one far-end of space to an other:

... -1-o-o-2-o-o-3-o-o-4-...

So 1 is far away from 4, and thus they can expand away from each other. But in-between there is 1 holding 2 due to gravity; 2 is holding 3 and so forth, linking everything together. Than how can 1 and 4 move away from each other, when they are indirectly hooked to each other due to gravity, doesn't it all add up?

@Chelle

Why does a gravitational attraction between 2 and 3 strong enough to cause them to merge imply anything about how strongly the 2/3 combination is attracting 1 or 4? Gravity reinforces existing irregularities. Some masses are so far apart that their separation is increasing faster due to the expansion of the space between them than it is decreasing due to their gravitationally induced acceleration towards each other within that space.

DavidL,

"Why does a gravitational attraction between 2 and 3 strong enough to cause them to merge imply anything about how strongly the 2/3 combination is attracting 1 or 4?

Because gravity works in all and both directions between the elements. And certainly when you start having things that are in a row and the amount of gravity emitted starts adding up, like in that image with all the canals, there you start to get a linkage tube-structure, that could hold things tightly together due to gravity. If gravity wouldn't be doing it's thing than there wouldn't be any of those canals.

chelle,

You are assuming that the matter in the universe is lined up in regular rows. That's not the case. Under the influence of gravity, matter tends to clump together. The real analogy would be something more like
1oooooo2oo3o4ooooooooooooooooooooo5

In that analogy, surely you can see that over the long term, 2,3, and 4 would tend to merge, but that clump would tend to separate from both 1 and 5. The actual structure of the real universe is clumpy, so this analogy models the real universe better. Galaxies in the same local supercluster that are moving together now will tend to clump together. Galaxies further separated and currently receding will continue to recede from each other.

Mark McAndrew and 'Wow'.
Stop being so preachy.
The reason is; if my question was already mentioned in the article, someone would tell me "Your question IS covered in the article." And I would read it. Saves time. Don't be upset, boys. ...and, still, no one has answered my question. So i'm assuming its not covered in the text, hence I will not read it.

Well that is exactly my point, if gravity between the coins on the balloon wins in 30% of the cases let’s say, than how can the balloon/universe be equally expanding, certainly when you look at that image with all the canals.

The universe can be equally expanding because the cases in which gravity wins are not some arbitrary 30%, they are exactly those cases in which you would expect the calculated force of gravity to be stronger than the calculated expansion of the universe.

Is this really that hard to understand? There's one force pulling things apart. Another pushing them together. For any two objects, you calculate the strength of the two forces acting on them. Theory is confirmed when the results of your calculation match empirical observation. If my head suddenly explodes due to the expansion of the universe, that is a serious problem for physics. But if my head stays together despite the expansion, that is not a serious problem, that is exactly what physics expects. Likewise, physics expects close, heavier coins to stay together on the balloon's surface while further apart and lighter coins do not.

How is this difficult to understand?

Chelle

I don't claim that there is no attraction between the merged masses 2 and 3 and outliers 1 and/or 4 , just that there is not enough to bind them.

In a universe created with stationary matter approximately uniformly distributed in a fixed and pre-existing "space" then what you say is correct, it will collapse

In a universe created by an explosion propelling material into a fixed "space" then some material will collapse back under gravity, but even here some may initially be given escape velocity and will avoid the collapse.

But we seem to live In a universe created with stationary matter approximately uniformly distributed in a rapidly expanding "space". This expansion has a larger effect than gravity for objects separated by vast distances. Some of the matter in such a universe is (and more will become) invisible to us because it is moving away from us faster than the speed of light. This cannot be gravitationally bound to our local galaxies.

lash, stop being so lazy.

You weren't bothered reading the posts before, why should anyone bother answering in another post when you have given indication that you don't want to read the answer?

Lads, the reason why chelle is finding it hard to understand is because chelle is trolling you.

eric,

"physics expects close, heavier coins to stay together on the balloon’s surface while further apart and lighter coins do not."

Well this is what I'm questioning, what is the distribution. When you look at that picture with the canals than you can see that there is a structure, where galaxies are closely packed together all through space, so it seems to be structurally tight (close) everywhere, than how can there be a global expansion?

DavidL,

"we seem to live In a universe created with stationary matter approximately uniformly distributed"

No we don't. There is a canal structure, a framework so to say.

btw it's not a problem of collapse or expansion because stuff is being pulled from all directions. There are 'knots' everywhere in that canal system, so it can't be expanding nor can it be imploding, it is keeping itself in balance, like a foam. Yes, there are immense massive 'knots' of clusters that are fairly equally distributed, but they are embedded in a gravitational construction that seems to, or has to, counter that expansion rate on a massive scale. See it as wires that connect the coins on the surface of the balloon either the wires also need to be stretchable, if they're not than they'll prevent the balloon from expanding, and AFAIK Gravity isn't stretchable.

Chelle
"No we don’t. There is a canal structure, a framework so to say."

Yes we do seem to live In a universe created with stationary matter approximately uniformly distributed. The canal structure, if that is what you chose to call it, is the result of gravity operating on the tiny original non uniformities. It will continue to do so until your canals become "lakes", of which all except the one we are in will ultimately become invisible to us.

"The canal structure ... will continue to do so until your canals become “lakes”,

I don't think that these canals can become a 'lakes', they are links that connect one knot to all the others with the force of gravity. Just like how our planet or Milky Way stays a tight 'coin' on that balloon, in the same way the wires/canals that connect the coins can't expand, there is one giant gravitational bonding structure.

Shades of "The canals of Mars".

There are "canals, structures, a framework so to say" in the packed surface of a collection of soap bubbles. The result of attraction and repulsion in tension with each other. No mystical forces at work, no fake pseudoscience needed. This, however, will never stop chelle from insisting that there is some postnormal woo going on...

Lakes aren't made of coins.

Chelle
"I don’t think that these canals can become a ‘lakes’, they are links that connect one knot to all the others with the force of gravity."

Whatever you think, current Theory (in the scientific not everyday sense) predicts they must. If you wish to postulate "canals" that prevent Gravity from being a universal omnidirectional force by constraining it to act only along them in complete violation of all known Physics, then a bit of supporting evidence would strengthen your case.

David L,

Of course gravity is omnidirectional, but you can't deny that just like our solar system is bonded and kept in place by gravity, that those canals are most likely relatively kept in place by gravity, and not just widening/spreading into lakes. Yes some galaxies lose energy and dissolve, but new ones are born as well out of clouds of dust in those canals, adding new fresh gravity to the construction, constantly renewing the strength of those structures.

Sorry David, but I guess everyone has to find out for themselves that chelle's a vapid troll.

Hopefully before your brain melts trying to parse out what the clucking bell she's vomiting up each time.

Wow,

Why don't you start your own blog instead of pretending that you are the host here, having the need to say you are 'sorry' for me participating here in the comment section, who do you think you are? If people don't like what I have to say or ask, than they can respond to that in their own way. But you picking on everything I say, and setting people up against me is just low.

I'm not pretending I'm the host any more than you are chelle.

You're trolling here and I'm commiserating those who are putting up with it. Don't like it? Go make your own blog and post there.

"..that those canals are most likely relatively kept in place by gravity, and not just widening/spreading into lakes"

Your concept of canals seems to be a description of the structure of the universe both as observed and as predicted by the Standard Model. There is no dispute at all that they are the result of gravity, but the issue is what will happen to them in the future. Perhaps my analogy of them turning into lakes was not a good one as you took it to mean expanding your canals. A better one might be that the canals become a string of increasingly isolated shrinking puddles. This is the prediction of the Standard Model. If you think this model wrong that’s fine. Work out how your universe would behave differently from the one described by the Standard model and devise experiments to show which is correct. This is the only way to distinguish a potential Nobel winning maverick original thinker from a serious case of the Dunning-Kruger effect.

Similarly your idea of “adding new fresh gravity” (i.e. mass) appears to violate the Standard Model in a major way unless you know more about Dark Matter than all the world’s Astrophysicists.

Incidentally a serious question for ETHAN if you are monitoring this thread.

When some M in our sun becomes equal to E/(C*C), our sun becomes a tiny tiny bit lighter, (strictly speaking, a tiny tiny bit less massive) our orbit becomes a tiny tiny bit larger, and some energy radiates out of the solar system. On a cosmic scale, does this energy somehow cause a gravitational effect, or is the entire universe slowly getting less massive too?

The energy does cause some gravitational effect, but it spreads out the energy and would reduce the curvature of the universe a little. The universe does get less massive. But GR's maths uses a tensor that includes energy as well as mass.

If you move some of the mass of the earth out beyond the geostationary orbit of satellites, then the orbit of these satellites gets higher.

The sun/earth thing is no different. Mass leaves the system within the earth orbit.

David L,

"... your idea of “adding new fresh gravity” (i.e. mass) appears to violate the Standard Model in a major way ..."

I was thinking here of star formation in molecular 'star dust' clouds in interstellar space, thus within those canals. I might be wrong but I thought that the bundling of matter, into stars and planets, would have a bigger gravitational impact (pull) along with the rise of dynamics generated by those new galaxies, than when they are just a cloud, so one could speak of 'new fresh gravity'. A cloud of matter can also be pulled and stretched apart from both sides, but a stellar object (star/planet) keeps itself together by rotating and pulls in all directions, there is a new strong link (galaxy) vs. the weak link there previously was (cloud).

"I might be wrong but .."

You are. You previously thought even defining "local" was a major issue, but now you are postulating gravity changes completely depending on the local distribution of mass. A cloud of matter consists of many small objects, how large and rare do they have to become before they transform into a group of "stellar objects" and suddenly exhibit totally different behaviour?i

DavidL,

"You previously thought even defining “local” was a major issue, but now you are postulating gravity changes completely depending on the local distribution of mass."

Defining local, and change of impact of gravity, are both related, as it the way that locally they are connected forming one giant structure, that on a larger scale has an impact preventing expansion.

"A cloud of matter consists of many small objects, how large and rare do they have to become before they transform into a group of “stellar objects” and suddenly exhibit totally different behaviour?"

When the stars are formed and start to shine light, there is a flip-over point.

For instance, you can use as a metaphor for SpaceTime a trampoline with a rock in the middle; and an amount of water also on it, that might be in total more massive than the rock, but as a result of weak bonding the water will flow towards the rock. Now freeze all the water into one block of ice and put it on the trampoline, than the rock will roll towards the 'water'. See how the individual parts of the clouds cannot pull something towards them, while if they are strongly bonded they can. The freezing point is the flip-over point. It is the same with that canal structure it is strongly bonded/connected on a 'local' scale, just like that block of ice.

Of course, there's no reason for any water in this analogy.

Chelle ALWAYS has to add some woo to her idiocies. Otherwise you might be able to follow them.

What else are stars and planets than condensed matter, just like a cloud of lose molecules that bond into water, or any other condensed liquid gas. It is wake up time, Wow, instead of woo time.

So even you don't understand what you are talking about.

Welcome to everyone else's world, chelletrolle.

Chelle,

This is pretty basic physics. Consider a spherical cloud of dust and gas, much like that which condenses to form a planet. Let the total mass of this dust cloud be M. Consider a test mass with a mass m. Let r be the distance between the center of mass of the cloud and that of the test mass. In the Newtonian approximation, the gravitational attraction between the test mass and the cloud is GmM/r^2.

Now consider what happens to the cloud if it collaspes under its own gravitation to form a solid body, ie a planet. Consider the cloud as an isolated system (valid since we're only considering what happens to the cloud under the influence of internal gravitational forces), and consider a reference frame in which the center of mass of the cloud is stationary. Now, the center of mass of the cloud cannot move unless there is an outside force acting upon the cloud. There may well be such forces in the real universe, but such forces do not come about SOLELY from the internal gravitational collapse of the cloud. Therefore, the collaspe of the cloud into a planet cannot cause a change in the location of the center of mass of the body. The collapse of the cloud into a planet also does not cause a change in the mass of the cloud. Therefore, the gravitational attraction between our external test mass and the newly formed planet would be GmM/r^2, which is the exact attraction that we found previously. Therefore, the gravitational attraction is unchaged whether we have a cloud of small particles or a condensed body doing the attracting.

Chelle;

Well this is what I’m questioning, what is the distribution. When you look at that picture with the canals than you can see that there is a structure, where galaxies are closely packed together all through space, so it seems to be structurally tight (close) everywhere, than how can there be a global expansion?

I think what's causing you problems is that the large scale distribution of matter does not match what your gut tells you it should be, if the universe is expanding. It just does not seem right to you that long strings of higher density will be stable if the universe is expanding.

There are really two issues here. First, your gut is wrong. Intuition is not a good guide as to what the universe 'should' look like if the laws of physics operate the way we observe them to. You need rigorous simulation to really get an accurate picture of what sort of large scale structure we should see, if our theories are correct. Rather than just toying with the ideas in your brain, if you put actual observed values into a high powered simulation, and look at the actual results, then yes, it turns out that the "canal"-like structure we see is a possible and expected outcome for a globally expanding universe with some initial minor heterogeneities.

So, I think at least part of your issue is just plain incredulity. This does not look like the outcome you think we should get from the math. My advice is: get over it. Thisis the outcome we get from the math. If it doesn't match your intuition, it is because your intuition is wrong, not because the math is wrong.

The second issue is assuming instability = instability on some human scale. You are right in that such large-scale structures are ultimately unstable. They will not last forever. The expansion of the universe will tear them apart. But you are talking about a many-billion-year process. We happen to have evolved while in the time period when they still exist. There is not much more 'why' to it than that. They are unstable; that does not mean they can't exist for the entire timespan of human civilization.

An analogy: if someone said "uranium is unstable. But there is some of it on earth. So physics must be wrong" you'd likely think them a nutter. The fact that uranium is unstable yet exists on earth is very obviously and uncontroversially explained by the fact that we evolved before it all decayed away. No overturning of physics is needed. Likewise, we happen to evolve during the era in which the large-scale structure of the universe is string-like.

It's not even multi-trillion year epoch until the galaxies are on their own (let alone the stars pulled apart). Something like a trillion trillion trillion trillion trillion trillion trillion trillion years before the local supercluster is wrested out from their local attraction if acceleration continues to go at its current inflationary rate (I think it's 8 repetitions of trillion, could be 8 repetitions of billion, though, I don't have my books here with me).

Chelle, I had typed up something similar to Sean T's post, but seems futile to post it now saying the same again

I would just add something regarding your SpaceTime metaphor (I think a better word would be "analogy", but call it what you will). The purpose of such of a metaphor/analogy
is to explain the observed behaviour of an unfamilar system in terms of the operation of a familiar one. Very useful it is too, but what you must not then do is to extrapolate your metaphor/analogy and expect it to reliably predict unobserved effects in the original system. Electricians by historical accident use the concept of electric current to wire up your house. There is no such thing, but in their professional environment current as an analogy of a reverse flow of electrons works fine. However, nobody would even have thought to try to design a CRT monitor using only this analogy; it would be like expecting to be able to design a machine that could suck shapeless lumps of lead into a tube from a great distance along with some local hot gasses, turning them into a bullet shape and some explosive, before putting them into the top a brass case

"Electricians by historical accident use the concept of electric current to wire up your house."

It was more "electrical fluid", hence the EE Doc Smith books going on about shorting out of electronics leaving pools of residue all around.

The model also had current going "the wrong way" from the actual flow (of electrons), hence electrons get the negative charge, because current goes the opposite way to the flow of electrons (the engineers got it wrong).

But this hop-scotch metaphor and extension to reality is chelle's troll bread-and-butter david. She won't give it up even for a big pot of honey.

Sean T,

"Therefore, the gravitational attraction is unchanged whether we have a cloud of small particles or a condensed body doing the attracting."

In theory maybe yes but not in practice because you are overlooking a number of facts. I made a drawing:
http://tinyurl.com/cloud-vs-knot

See how a 'cloud' is a 'weak' thing, it is being pulled apart and hardly plays any role, but when rotating Stars, Planets and Galaxies are formed than you do have again a 'strong' link that holds everything together. This giant gravitational structure is a giant equivalent of what happens on smaller scale.

eric,

"It just does not seem right to you that long strings of higher density will be stable if the universe is expanding."

It isn't a matter of what seems to be right or not, it is a matter of can it work or not. And a gravitational construction shouldn't allow an expansion to happen. It is very simple; the Milky Way isn't expanding because gravity is keeping it together, the same goes for this giant construction that is holding everything together. Either the 'expansion' isn't countered by gravity, or it is. But than the Milky Way has to be stretched apart, you can't star cherry picking when or where Gravity works or not.

DavidL,

Same answer here as Sean T, look at the image, of course a trampoline is moderately useful but in this case it made perfect sense. You need to look at the reality of things.

Wow,

You stink.

"It was more “electrical fluid”, hence the EE Doc Smith books .

Not really familiar with EE Doc Smith, but this seems to be harking back to an earlier analogy: explaining electric current in terms of rate of water flow through a pipe and voltage as the pressure head

You'll also get to know chelles predilection for making pointless and unenlightening diagrams and pretending they are of some purpose.

Just don't forget to use earplugs when trying to work out what byzantine circular "logic" chelle spouts.

"In theory maybe yes but not in practice because you are overlooking a number of facts."

Him and every scientist from Isaac Newton downwards. To a scientist, finding where "In Theory" deviates from "In practice" is the start of the path to a Nobel Prize. You need to send your drawing to The Royal Swedish Academy of Sciences (info@kva.se) and get your application started.

"You need to look at the reality of things"

Chelle, perhaps you should listen to your own advice. Anybody can draw something. Scientists check their drawings against observed reality and keep re-drawing them until the agreement is as close as possible. Even Einstein's ideas could have been trumped by reality.

the Milky Way isn’t expanding because gravity is keeping it together,

Correct. The space in which the milky way exists is expanding. The atoms (of the milky way) themselves don't expand, the space they occupy does. Every time the distance between atoms increases by an infinitesimal amount, the other forces pull those atoms back together, becuse on a local scale, the other forces are stronger. Like magnets on a balloon, the balloon can expand under the magnets while they stay together.

the same goes for this giant construction that is holding everything together. Either the ‘expansion’ isn’t countered by gravity, or it is.

Eventually the expansion will win out over these big structures, and we will be left with island galaxies, because over large distances, the expansion is stronger (place the magnets very far apart on the balloon, and their attraction won't hold them together). But its irrational for anyone to think that because the process hasn't completed by September 13 2012, it must not be happening at all.

DavidL,

"To a scientist, finding where “In Theory” deviates from “In practice” ...

There is no deviation from Newton's Gravity or Einstein's General Relativity, it is how you or Sean T wanted to apply it, that is wrong and how you are overlooking some facts.

eric,

"Like magnets on a balloon, the balloon can expand under the magnets while they stay together."

The balloon can't expand because the magnets or coins are linked by gravity-wire's that are the canals/links of that giant structure, that is what you are overlooking along with the difference of impact of a lose Cloud of matter vs. a Structure of matter.

Expansion of space is most likely wrong, we observe an expansion because the day our galaxy started to form we started to effect the incoming light from other stars, it is us who are causing the effect of expansion, we are expanding into space, it isn't a major outside thing that is going on.

Word salad.

Nom nom nom.

"how you are overlooking some facts."

Only "facts" which require the revision of existing Theory.

Clhelle, it is central to Newtonian Mechanics that a group of masses can be replaced by a single mass located at their common centre of gravity. This applies whether the masses are dust, planets, stars, (emitting light or otherwise) or black holes. Where was Newton wrong exactly?

The balloon can’t expand because the magnets or coins are linked by gravity-wire’s that are the canals/links of that giant structure, that is what you are overlooking along with the difference of impact of a lose Cloud of matter vs. a Structure of matter.

I have to agree with Wow, your comment here makes very little sense to me. I do not understand what you are trying to say. If it's that space which is deformed by gravity can't expand, I'd ask why and where you got that rule from. I see no prima facie reason why it can't. Go back to the old high school metaphor of a bowling ball on a rubber sheet, and it is pretty easy to visualize how the rubber sheet could simultaneously be deformed by the ball and stretched at the same time.

It's like saying that actual, real-world wires can't expand if there's a force greater than the elasticity of the wire pulling it apart.

Which is to say, like usual, even the analogy that is being mis-applied doesn't work they way Chelle thinks it does.

But here we are all engaging them, so mission accomplished from their point of view. I'm stopping now; suggest others do the same.

It's also like saying wires are lines drawn on a graph paper which means that there is a pencil in the sky, hence proving there is a cosmic Woolworths, because you could have bought your pencil and ruler from Woolworths before it closed down.

I.e. a load of bollocks segueing from one ill formed analogy into several others before coming to a ridiculous conclusion about how all science is wrong.

I'm getting pretty good at doing a chelle, aren't I.

DavidL,

"it is central to Newtonian Mechanics that a group of masses can be replaced by a single mass located at their common centre of gravity."

That is not the whole truth, you need to refresh:
http://en.wikipedia.org/wiki/Center_of_mass

For instance a cloud is not a rigid body, while a Star is, and then there are all types of motions involved ...

eric,

"it is pretty easy to visualize how the rubber sheet could simultaneously be deformed by the ball and stretched at the same time."

Yes, one can stretch things such as a balloon, but if you look at our Solar System or the Milky Way (the coins on the balloon) they aren't stretched by the Expansion of Space, so Gravity isn't stretchable it simply keeps things in its place. The point that I'm making here is the fact that the giant Canal structure is made out of Gravity links, so when things on a small scale can't be stretched, than how could it be possible on a large scale?

"That is not the whole truth, you need to refresh:"

I need to refresh! Did you even read., let alone understand, your wiki article? The first paragraph:
"In physics, the center of mass or barycenter is the weighted average location of all the mass in a body or group of bodies. Various important calculations in mechanics become simplified when quantities are referenced to the center of mass, or when the entire mass of a body is treated as if it is concentrated at the center of mass."

differs only from what I said in using American spelling. Can you indicate a single sentence in that article that supports your assertions about the behaviour of groups of masses?

That's another thing you'll find about chelle. She'll put a link up that says something that indicates she's wrong as if it proves her right.

AGW deniers and xtian YECs do this all the time, though in the case of the YECers, they'll generally go to AIG or similar WUWT-like sites and not try to link to genuine sites.

Just watch chelle insist that you're doing it wrong. You'll only ever get "you're doing it right" if you pander to chelle's ego.

David L,

In the case of a rigid body, the center or centre of mass is fixed in relation to the body, …

In physics, a rigid body is an idealization of a solid body of finite size in which deformation is neglected. In other words, the distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it.http://en.wikipedia.org/wiki/Rigid_body

Now for a cloud everything can shift, and things can be pulled apart. What is so hard to understand about the difference between a solar object, and a cloud of dust … pfff …

Notice the definition is an idealisation. There is no such thing as arigid body in the real universe. All objects deform in response to applied external forces. Even Jupiter's piddling gravitational field can turn its moons to mush. You are trying to draw an imaginary line again.

The solar system is not a rigid body. The galaxy is not a rigid body. In any body, a force stronger than that holding it together will pull it apart. Gravity does not hold things in place, it attracts them, and anything pushing away harder than gravity pulls will overcome it. This is how rockets work...

And then you have a phenomenon which is very small but constant across space, so very close things are not pushed apart much and gravity dominates, but over very large distances this effect dominates.

What's so hard to understand about that?

"What’s so hard to understand about that?"

The bit that tells chelle she's wrong, of course.

No kidding. And I did it again, didn't I? I'm sorry. I'm really, really done now.

"…but over very large distances this effect dominates."

There are no 'very large distances'. Those canals are dense structures, just like a cable is a dense structure, expansion can not pull these canals apart, they are loaded with gravitational knots keeping everything tight. You keep on forgetting that gravity adds lineary up in these canals.

Wow,

"You say it best when you say nothing at all"

http://www.youtube.com/watch?v=0jYfpkI5VuA

chelle this is you, this is:

http://www.youtube.com/watch?v=B3CT9f2ULIw

Alternatively:

http://demotivators.despair.com/demotivational/cluelessnessdemotivator…

Or, most appropriately of all:

http://demotivators.despair.com/demotivational/incompetencedemotivator…

And lastly:

http://www.despair.com/stup24x30pri.html

Wow! Very impressive!

http://www.despair.com/believeinyourself.html

Wow! That's even more amazing!

Hey, you seem to enjoy it.

http://www.despair.com/compromise.html

Then again, you're easily impressed.

LOL :D

Does not Hubble discovery contradict Newton's second law?
We say that the further a galaxy gets from us the faster it will.
In other words they accelerate. To accelerate you need a net
force. Where does this net force come from?

That's right, like CB's rocket that needs to work and lose energy to get away from earth and escape gravity, clusters would need to lose energy, to expand away from each other, and we don't do that.

"Stretching an uninflated toy balloon causes it to release heat and become hot."
https://webspace.yale.edu/chem125/125/history99/9Thermodynamics/Disorde…

Chelle, you moron, the universe is expanding. That is the source of energy that makes the galaxies further apart. But if the overall energy is still not enough to make a stable orbit, the orbit will decay and the two entities will get closer overall.

They will, however, get closer LESS QUICKLY than if there were no expansion.

There is no balloon.

As always, you reify the analogy and pretend it is actually real (like your earlier statement about how your METOPHORICAL water somehow must be real becauase water exists in reality).

This is because you're as thick as a yard of lard and moreover wish to troll everyone here because you're a sick fuck.

The stretched balloon is getting warm because each point is losing (bonding) energy. Now our Earth doesnt lose energy when a rocket moves away, but if we want to move away from all the other planets in the universe, than we have to put in work, certainly when there's an acceleration just like 'Reza Bokat' says. So this force has to come from within us, and thus we should lose energy to counter Universal gravity that we can witness in that giant canal construction, but it turns out that there is no such thing because our Milky Way is not expanding, in fact gravity works just fine.

"There are no ‘very large distances’"

So Chelle, care to give us an estimate of the size of these canals? An approximate diameter and typical length? Order of magnitude estimates will do for now. 10 light years or 100 light years?

An apology about the analogy v. metaphor thing. I did a web search as a refresh on the difference, and came up with this:

"Analogy basically gives similar relationship to two things while metaphor replaces the meaning of one word with another."

So it seems that yes, you only ever use metaphor. Analogies are for those who understand what the are trying to explain, metaphors for those who don't.

"So Chelle, care to give us an estimate of the size of these canals? An approximate diameter and typical length? Order of magnitude estimates will do for now. 10 light years or 100 light years?
"

Look at the image I posted here in my comment on September 11, 3:40 am, or let me post it here again ... voilà:
http://scienceblogs.com/startswithabang/files/2012/08/millennium2zoom_p…

Thanks for the 'analogy vs. metaphor' thing.

"The stretched balloon is getting warm because each point is losing (bonding) energy."

WRONG!

The stretched balloon is getting warm because work is being done on it.

"Does not Hubble discovery contradict Newton’s second law?"

It does not.

"The stretched balloon is getting warm because work is being done on it."

You are right, it are the points that apply the force and stretch the material that are losing energy, so when planets are moving away from each other, it are those points that do the work and need to lose 'bonding' energy, just like CB's rocket needs to lose energy, and do work to 'break away' from Earth.

Now when we look at ourselves, as a point, we aren't losing energy but according to Expansion of Space, we should be losing lot's of energy because we are accelerating away from all the Stars in Deep Space, shrinking within that giant structure.

"it are[sic] the point"

Snrk.

"so when planets are moving away from each other, it are those points that do the work "

What points? THERE IS NO SPOON.

Space is expanding. Not a substrate, not an aether. Not a substance. Not a trampoline, not water not ice not rocks not rubber.

Chelle, how you got a passing grade from physics in high school is beyond me...

Be it classical physics or QM and GR, you just don't know it.

Chelle can you explain the dimensions of the canals from the scales on those images, as I am not sure I understand them. My impression is that they are about 1million light years in diameter. Am I reading them wrongly, or do you regard millions of light years as being something less than 'very large distances’?

@ Sinisa Lazarek Are you making an unwarranted assumption?

Wow,

"“it are[sic] the points”

Snrk.

That is simply wrong, to misquote me and than act all funny as if there was a spelling mistake?

Space is expanding.

Your Stars can't be moving along with that Expanding Space, because gravity is keeping those clusters in place, that is the problem. Look at the image linked to below, and see how there is a 'valley' in SpaceTime where a canal is and where gravity links those clusters:

http://tinyurl.com/canal-valley

If you want to expand that structure by expanding space, than Space needs to be a substance that is like a gas that is expanding, and that applies pressure on the elements, and which is doing the work. If so than you can start to push all the clusters away from each other, otherwise the force has to come from within the clusters itself and that is not possible because it would be like 'Reza Bokat' suggested, 'contradict Newton’s second law'. And the interesting thing is that SpaceTime is all about gravity, so no Space cannot just expand without something applying a Force in-between the points. Just like an expanding balloon is the result of more gas being added on the inside pushing all the coins further away from each other, no expanding gas no expansion, and looking at the canal-structure it is even not possible that everything is equally expanding away from us. The only solution for Red Shift *effect* is that space around us is gradually getting denser, dimming down the incoming light.

DavidL,

The dimensions are in Megaparsecs and a 'Parsec' is about 3.26 light-years.

"to misquote me"

You don't even understand how to scroll up??? I didn't misquote you, dipstick.

And David would now like to ask you why megaparsecs are "local".

http://en.wikipedia.org/wiki/Sic

"so no Space cannot just expand without something applying a Force in-between the points."

If that were true, then Newton's second law would be false.

A constant relative speed between two objects in free space will increase their distance from each other by a constant amount UNLESS you apply a force to one of them to stop the motion.

You really are a retard, chelle.

"The dimensions are in Megaparsecs and a ‘Parsec’ is about 3.26 light-years."

I know what a parsec is, so as your understanding of the diagram you posted is similar to mine, are we are agreed that you regard a million light years as not a "very large distance" ?

I am struggling to understand your previous post, but maybe this is because you are too. Are we also agreed that the expansion of the universe is moving the grid lines of your canal-valley diagram further apart in both axis (increasing the gravitational potential energy between the red balls in the process), and that gravity will be trying to pull the red balls together again, causing them (and their distortions) to move towards their mutual centre of mass with respect to the grid lines?

"The only solution for Red Shift *effect* is that space around us is gradually getting denser, dimming down the incoming light."

This is just so wrong. Getting denser how? What is there more off, exactly?

But just from top of my head. If space is getting "denser" that would in effect cause i.e. electric constant to change, thus resulting "c" to change, etc. etc. all those are measurable values. And we haven't seen them change. So.. another theory plz, since your "only solution" is pretty sucky.

Chelle means that the only solution to the Red Shift seen that allows her to keep pretending there's an Aether is that space around us is getting denser.

Nothing else is required, just that she can continue to prattle on about how there really is an aether.

Despite everyone else having discovered it's a load of bollocks.

Wow,

" I didn’t misquote you"

Yes you did. you left out an 's' at the end of points, when you quoted me. When I quoted you, I highlighted with 'bold' the 's' that was missing.

“so no Space cannot just expand without something applying a Force in-between the points.”

If that were true, then Newton’s second law would be false.

A constant relative speed between two objects in free space will increase their distance from each other by a constant amount UNLESS you apply a force to one of them to stop the motion.

Oh great, so now when I trow a ball, it is no longer moving, but it is the space between the ball and my hand that is expanding, super! And stars that are seemingly moving away, happens because space had a push one day and it keeps on going, expanding, dragging everything along with it. The connection between space and matter is even stronger than gravity, btw I thought that it was Space that was curved by Gravity and besides that simply flat, but now Space has mass as it can pull other mass along with it, well what is the mass of a cube of Space, that is flying into space?

DavidL,

"Are we also agreed that the expansion of the universe is moving the grid lines of your canal-valley diagram further apart in both axis (increasing the gravitational potential energy between the red balls in the process), and that gravity will be trying to pull the red balls together again, causing them (and their distortions) to move towards their mutual centre of mass with respect to the grid lines?"

This doesn't make any sense. First of all there 'is' no expansion; and second gravity is not pulling them 'again' together, because there 'was' no expansion; and third, what's up with you and this 'mutual centre of mass' can't you see how the canal system distributes the effect of gravity into a structure, like I said a couple of times now gravity adds up when you put things in a row behind each other, it are those canals!

Sinisa,

"If space is getting “denser” that would in effect cause i.e. electric constant to change, thus resulting “c” to change, etc. etc. all those are measurable values. And we haven’t seen them change."

Yes 'c' changes as it is dependent on the excitement of the Aether, we have discussed this before. And no it is not a measurable value, how can you measure the difference between the density here and that of a lightyear away from here, it's like measuring the water temperature in the Mediterranean and wanting to prove that there is colder water on the north-pole.

"Yes you did. you left out an ‘s’ at the end of points, when you quoted me"

Yup, retard.

Did you read what Sic stands for? Did you see where [sic] appeared?

Yes, you did, but you're a retard troll who has no purpose but to be a complete dick.

"Yes ‘c’ changes as it is dependent on the excitement of the Aether"

Wrong! Without even going into the discussion about "ae" with you.. i said before it's pointless.

If there were any changes in "c" for whatever reason, and depended on anything, the spectral lines from galaxies would be all over the place in total random order. Again, this is not observed. Sorry.. you're explanation sucks again. :D

@DavidL
" Are you making an unwarranted assumption?"
oh believe me, it's very warranted

Chelle, I think you have grossly overestimated the density and uniformity of the 'tubes' of structure in the universe.

However as your own link to the zoomed-in images of the cosmic structure shows, certain galaxy clusters may be dense but the filaments between them are not. So in reality, there really are "very large distances" between gravitationally bound structures. You have turned a qualitative eye-balling of an image into a falacious quantitative statement.

For example, as explained in Ethan's post, outside the local group, the next closest structures are so far away that their gravity cannot hope to overcome universal expansion in the long term. For this not to be the case we would need many more galaxies evenly spaced between us and the components of the larger supercluster. And this is not the case.

@DavidL
” Are you making an unwarranted assumption?”
oh believe me, it’s very warranted

I meant the assumption she got a passing grade from physics.

Chelle

Please define "rigid body" and please describe how one behaves differently from a non-rigid body. Neither GR nor the Newtonian approximation make such a distinction.

Now, if you want to argue that external gravitational forces could influence the cloud of gas and dust to a greater degree than they would a planet, maybe I can understand your argument. However, it's still wrong. An extended body (whether rigid or not, whatever that might mean), can, for the purposes of predicting gravitational interactions, be replaced by a point mass located at the body's center of mass. That's true whether the body is a planet or a dust cloud. External bodies will influence both in exactly the same way, namely an external body will cause the center of mass of the body to accelerate.

The only difference between the two cases is intuitive, not rooted in physics. Take, for example the gravitational interaction between a falling object and the earth. We normally state (at least in classical physics terms) that the falling body has been accelerated. We would be equally correct in stating that the earth has been accelerated. The force acting on the falling body and the force acting on the earth are the same. The earth accelerates less, though, because its mass is much greater.

In similar fashion, the center of mass of a planet or a dust cloud will be accelerated equivalently by an external body (asssuming, as I have been that the mass of the dust cloud and that of the planet are equal). The result will be more noticeable for the dust cloud. The various particles can shift around more or less independently, so we would notice as change in the size and/or shape of the cloud, whereas with the planet, we might not notice anything. The point remains, however, that the acceleration of the COM is identical in both cases.

Chelle,

"A cloud of dust can be pulled apart..."

By which, I suppose, you are implying that a planet (or other planet-like "rigid" body) cannot be pulled apart? Have you ever looked through a telescope at the planet Saturn? Did you notice those rings that surround the planet? Where do you suppose those rings came from?

Sinisa,

"If there were any changes in “c” for whatever reason, and depended on anything, the spectral lines from galaxies would be all over the place in total random order."

Light would be scattered when it would be slowed down by an other object in the Aether, not when the Aether itself is has a small density difference. An arrow shot on a cold day will still move straight forward as being shot on a warmer day, only when it is raining it will start to 'scatter', see the difference.

Sean T,

Ridgid or not is a matter of being 'connected' or in orbit (rotational momentum) vs. 'stationary' and independent molecules, or how easily you can pull things apart. For instance it is harder to stop a planet rotating around a Star, than pull the same amount of dust into one direction, an other example is when you pull on a feather or any other rigid body, you pull the whole feather along because it is chemically bonded in a stronger way than a 'cloud' of particles. Or do you find that the particles of a cloud are as strongly connected as in a gas-giant?

Chelle, you're a sick fuck, you know that?

Troll right the fuck off.

"An arrow shot on a cold day will still move straight forward as being shot on a warmer day..."

OMG! On what planet do you live??? Do things fall up on your world??
On this planet, Earth, the cooler the air will slow the arrow more than the hot air, the rain is irrelevant. Your whole talk is irrelevant since it's not based on reality. The fact you can't even properly defend it, is the icing on the cake.

You introduced "density" .. now live with it, you can't wiggle your way out of it once seeing how it blatantly fails.

Sinisa,

"On this planet, Earth, the cooler the air will slow the arrow more than the hot air ..."

Exactly, and it will only be curved by gravity.

Wow, what a spectacular choice of words!

"when you pull on a feather or any other rigid body, you pull the whole feather along..."

Not necessarily, and that's my point. For instance, you could attach your feather (or other rigid body) to very strong cables at two distinct points. You could then attach each of these cables to the tail of a 747 aircraft. Now if these 747's proceed to pull the feather in opposite directions, is the whole feather really going to go along or is it going to tear in half, thus becoming a non-rigid body?

That's really my point; given a strong enough force pulling a body apart, there's no such thing as a rigid body. This doesn't change the physics of gravitation, however, as I outlined above. The center of mass of the cloud and the center of mass of a planet move the same way under the gravitational force of an external body.

It is no harder or easier to pull a cloud of dust in one direction than it is to pull a planet of the same mass in one direction. It is true that there's less of a connection between the individual dust particles than there is between the individual particles making up a planet. Therefore, when you bring an external mass near a cloud of dust, SOME of the dust particles will indeed move toward the external mass. However, not ALL of the particles will do so, only those nearer to the external body. For the planet, ALL of the particles will move toward the external body, just that they will move a much smaller distance than the dust cloud particles. The COM's move in the same way, however.

You seem to like analogies that have questionable applicablility to the question at hand, so let me present one of my own to you. Suppose you are protecting a loved one from an animal onslaught. You have a choice of protecting your loved one from a charging elephant or a swarm of bees with the same total mass as the elephant. (Assume that your loved on is allergic to bee stings and will die if he/she is stung, and further assume that the elephant will trample him/her to death). Which one is easier to protect your loved one against? Personally, I'd choose the elephant because given a big enough gun, I'd have a pretty good chance of conclusively stopping the elephant. With the elephant-sized bee swarm, it would be too hard to make sure none got through. Of course, as I've said, this has questionable applicability, but hopefully it gets the nature of the problem through to you.

"It is true that there’s less of a connection between the individual dust particles than there is between the individual particles making up a planet"

Remember the dipshit is talking about gas giants where there's also nothing to hold on.

Sean T,

You are correct when it's about you & your partner as a duo vs. a swarm or an elephant, it is a two 'body' situation. But you when looking into space and that giant canal structure you are talking about interplay between multiple elements. So in a two body-setting you can pull a 747 forward without breaking, but when there are multiple objects involved it becomes difficult.

So when you have for instance a harem of 13 girls, than those bees will split up in 13 groups, the elephant can only go in one direction. In that case I would also pick the elephant and have him trample that only one chick, leaving me with 12 others. Now imagine us hanging all in space with the white elephant in the middle, than we all would all move towards the elephant vs. the bees would we would pull towards us, because our rigid body is more strongly connected ... although this again depends on how we are connected to other elements ... see how it becomes an interplay of a group vs. an individual, AND distance.

btw In my comment on September 13, 1:00 pm, I also quoted a piece from wikipedia on what a rigid body is and it says clearly that it is an 'idealization', so yes it is all relative, but not irrelevant.

"In physics, a rigid body is an idealization of a solid body of finite size in which deformation is neglected. In other words, the distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it." http://en.wikipedia.org/wiki/Rigid_body

Anyway let's look back at why I brought this concept up in my comment on September 12, 1:01 pm:

"Yes some galaxies lose energy and dissolve, but new ones are born as well out of clouds of dust in those canals, adding new fresh gravity to the construction, constantly renewing the strength of those structures."

It was to point out that the parts that make up that giant structure renew themselves all the time, so when you look at the proposed Expansion of Space that is supposedly pulling everything apart, than you also need to look that refreshing structure based on mass and gravity, being a pretty solid thing, that is actually holding everything in place over time and distance.

Chelle: "Now imagine the bees are carrying strawberry flavoured lollipops and the elephant wants an autograph. Therefore there's the aether."

Wow,

Yes, the Aether is here, there and everywhere …

http://www.youtube.com/watch?v=Vd9HrO1b7pk

"Nobody can deny that there's something there"

Hobby Everly,

I overlooked your post. You are definitely right that space in between is very large and seems to be too large. That is the essential question. But the picture of those canals shows us that structures are in fact there, and they are based on gravity, if you would be right than no structures would develop. What you are missing is that gravity adds up, forming valleys and canals as earlier suggested, and than what looks like some lose clusters becomes part of a rigid construction, a bit like a spider web or the Eiffel Tower.

No, there is no Aether.

Michelson Morely experiment proves it doesn't exist, you peabrain idiot.

"No, there is no Aether."

Ahem, there is no Aether 'observable'.

NWOR.

Well Chelle, after picking up this thread after a weekend away, I am beginning to think that under that polite exterior you are as mad as the proverbial Hatter, though I do wonder if you inspired Ethan's "Its never too late -- to do science" post.

"Ahem, there is no Aether ‘observable’"

Indeed! Like Ley Lines, Fairies, Leprechauns,Yeti the Flying Spagetti Monster and any other of the tens of thousand of deities from cultures past and present. Whatever these deities may have done in the past, they all seem incapable doing anything now that has any observable effect whatsoever on the universe. Your Aether goes one step further. Not only is it never observed, it seems to deliberately get out of the way whenever we try to measure it. As GPS satellites whizz around the earth it seems to disperse around them so as to delay or speed up their signals by not even a femtosecond more than general relativity predicts..

Consider a thought experiment. Imagine your feather and an identical one placed stationary with respect to our sun and away from the gravitational influence of the other planets.Let both drop towards the sun, but before doing so, cut one of them into pieces, How many pieces must you cut this feather into before those pieces fall at a different rate to the intact feather? Is this dependent on how far apart you move the pieces?

To summarise your ideas as I understand them.

Gravity is not just proportional to mass, but is also a function of both what for the sake of argument I shall call the nebulosity and the rigidity of the mass involved. The meaning of these terms can be redefined at any time when necessary to fit your arguments.

A lot of scientists have worked for a long time to produce a Theory of development of the Universe. A computer program based on this Theory simulates the universe from t =(approx)0 to t =13.5 billion years and comes up with something that looks like the universe we observe. You are happy to accept this prediction and the resulting universe of your knots and canals, but otherwise they have got it all wrong. You clearly believe the structure of the universe is dynamic, so what do you think it looked like a billion years ago? (As you have already accepted the width of your canals is only a "not very large" distance of a few million light years and their length a few hundred million light years, your network is only visible to us in a universe at least a billion years old. )

DavidL,

First of all I'm not alone about this Aether thing, Einstein also said there is one, only not observable (see the debate at post "Can You Get Something For Nothing?" Feb. 2, 2011). Second your argument about GPS satellites is interesting because if there would be no medium than light would have no maximum speed, what would be limiting it, and what would be causing time dilation?

So why aren't we able to observe the Aether, it is in line with my comment on the Happy Gilmore post, that rotation and profile reduces the effect of a 'medium' slowing down the Golfball. You need to look at a photon as a kind of closed looped eddie in a Medium, it is governed by it's own being and isn't affected by any 'wind', the Medium has little grip</i< on the 'object'. It cuts like a knife through butter, so to say.

Regarding the feather; cut in pieces, or as a whole, it will fall at the same speed towards the Sun, it's a matter of scale. But look at a rotating gyroscope it doesn't fall at all to the ground, and seems to be weightless: http://youtu.be/cquvA_IpEsA

Imagine it being a non-rigid structure of dust, ...

"A computer program based on this Theory simulates the universe from t =(approx)0 to t =13.5 billion years and comes up with something that looks like the universe we observe.

Well at Pixar Animation Studios they can roll out a movie such as Brave out of their computers, it also looks very much like real people we observe, I'm not impressed. A good bookkeeper can make anything match therefor it is not scientifically solid.

You clearly believe the structure of the universe is dynamic, so what do you think it looked like a billion years ago?"

I believe that a billion years ago, it looked very much like it looked now perhaps slightly different, I'm only saying that we can't tell from our perspective, and that what we say are the *symptoms* of the Big Bang, e.g. Red Shift is only an *effect* due to the birth of our Milky Way in the Universe, which is ever expending and emitting light and gravity further into the giant bath of Aether, that the Universe is. So what we see is our own little Bang, not that of the Universe.

btw I think you might be right that Ethan’s “Its never too late — to do science” post might be inspired by our debates, seems like all can learn a *new* thing or two, if you manage to over come and adjust your existing Muscle memory that says that there is NO Aether.

Agh, sorry for the badly closed bracket, and often bad spelling, I wish there was a 'preview' and that I was a good speller.

"Einstein also said there is one"

Continuing to lie, chelle?

“All our attempts to make ether real failed. It revealed neither its mechanical construction nor absolute motion. Nothing remained of all the properties of the ether except that for which it was invented, i.e., its ability to transmit electromagnetic waves. Our attempts to discover the properties of the ether led to difficulties and contradictions. After such bad experiences, this is the moment to forget the ether completely and to try never to mention its name.”
(The Evolution of Physics Einstein 1938)

For someone whose only claim to veracity is "Einstein said it", you really do have a problem with agreeing with Einstein.

Wow,

Seems you are still not able to flex your mind, to what you've been thought at school, and what the professor said.

chelle, seems like you're blind.

you: "Einstein says there's an aether!!!"

Then, when you're shown him saying he spend years looking and couldn't find it and therefore concluded that it doesn't exist:

"You're not flexing your mind".

Tell me, how is flexing your mind to ABSOLUTELY IGNORE what Einstein said indication of flexibility rather than ideological blindness?

Chelle,

As I've asked you before, what difference does it make whether or not Einstein thought the aether exists? Either it does or does not, regardless of Einstein's opinion of the matter. You are clinging to an argument from authority.

Further, what evidence is there that an aether does exist? If it does, it must have no observable properties and no observable effect on the rest of the universe. Cling to the aether if you must, but there's really no reason to believe it exists; physics works without it. The fact that you can't seem to believe that this is the case seems to be nothing more than an argument from incredulty on your part and is just as much a fallacy as your argument from authority.

Einstein's thought on the matter was after 18 years of looking, it couldn't be found, therefore doesn't exist.

But chelle wants to pretend those 18 years didn't happen and that her idiocies are valid because Einstein said so once before (and then changed his mind, unlike chelle).

Sean T,

"… physics works without it."

The Wave- Particle duality that comes out of the Double-Slit experiment shows that there is a medium, if there is no medium than this *effect* is impossible. Mathematically we have come up with a statistical solution for this phenomenon, but that doesn't take away that there is a medium. So simply put the math works without it, but not nature. That is also what Einstein said, it needs to be there for nature to 'work' but there's no way we can measure it because our measuring tools are build around the exchange of photons ... so we have to give up on trying to find it. But now we can do CFD simulations, this opens a new door for trying to figure out how this Aether might work. Not trying this because there is supposedly NO Aether is keeping science once again in the dark ages.

"The Wave- Particle duality that comes out of the Double-Slit experiment shows that there is a medium"

No it doesn't.

No Chelle, the effect is quite possible without a medium. It's your understanding of it that is lacking. Positing a medium just speaks to your own incredulity, ie "there must be a medium because I can't understand how you can account for this effect without one."

In reality, the wave-particle duality that you think presents a problem for the lack of aether is a problem only in your mind. No medium is necessary to explain wave-particle duality, or any other quantum effect. Wave particle duality mostly is a result of our human tendency to classify seemingly different things into different classes. We made a mistake with waves and particles, however. Waves and particles are not inherently different, as becomes apparent on small scales. There is no "duality"; quantum entities are BOTH waves and particles. It's just that our measuring devices distinguish one or the other aspect of these entities. No need for a medium; all quantum entities have an amplitude and a phase, and can therefore interfere with themselves destructively and constructively to form the interference patterns that arise in the double slit experiment.

BTW, if you insist on continuing to use Einstein as the source for your arguments from authority, I feel obligated to inform you that in the realm of quantum mechanical phenomena, Einstein is far from an authority. In fact, Einstein, both by his contemporaries and by current physicists was generally considered to have been completely wrong in his ideas. For instance, he believed that the randomness at the heart of the "statistical solutions" that you seem to denigrate was not real and was a manifestation of our lack of knowledge of "hidden variables". Well, I forget the exact experiment (someone else feel free to help please) but it was found that Bell's inequality holds, which implies that either there are no hidden variables or that reality is non-local (which would have APPALLED Einstein). So Einstein's saying that the math works but nature doesn't is not particularly compelling.

"if there is no medium than this *effect* is impossible."

If for the sake of argument we assume this to be true, then you need to define the properties required of that medium. You can call it Aether if you like, and insist that lo EM radiation travels through it at a constant speed c. The one defining property that we know it must then have from every experiment that has ever been done is that each and every observer must somehow drag with him both his local Aether, and the Aether through which any of his experimental photons have traveled.

And how has your billion year old universe been expanding into the Aether without any changes in form? What is causing it to expand when gravity should be continuously pulling it together?

Sean T,

" In fact, Einstein, both by his contemporaries and by current physicists was generally considered to have been completely wrong in his ideas. For instance, he believed that the randomness at the heart of the “statistical solutions” that you seem to denigrate was not real and was a manifestation of our lack of knowledge of “hidden variables”. Well, I forget the exact experiment (someone else feel free to help please) but it was found that Bell’s inequality holds, which implies that either there are no hidden variables or that reality is non-local (which would have APPALLED Einstein)."

I used Einstein in this debate here, in the first place not say that what he says is right or wrong, but because DavidL started to bring up a bunch of nonsense because I spoke about the fact that the Aether is not observable. This is a normal physics argument and not the stuff what fairytales are made of, which he wanted to suggest it is. And no, it is not all like the Copenhagen interpretation want us to believe it is, check this Double-Slit experiment: http://www.nature.com/news/2011/110602/full/news.2011.344.html

"Intriguingly, the trajectories closely match those predicted by an unconventional interpretation of quantum mechanics known as pilot-wave theory, in which each particle has a well-defined trajectory that takes it through one slit while the associated wave passes through both slits. The traditional interpretation of quantum mechanics, known as the Copenhagen interpretation, dismisses the notion of trajectories, and maintains that it is meaningless to ask what value a variable, such as momentum, has if that's not what is being measured."

And check the Pilot-Wave theory Wikipage:

The Pilot Wave theory is a hidden variable theory. Consequently:

• the theory has realism (meaning that its concepts exist independently of the observer);
• the theory has determinism.

The positions and momentums of the particles are considered to be the hidden variables. The observer doesn't know the precise value of these variables which introduces uncertainty into the theory.

A collection of particles has an associated matter wave, which evolves according to the Schrödinger Equation. Each particle follows a deterministic (but probably chaotic) trajectory, which is guided by the wave function; collectively, the density of the particles conform to the magnitude of the wave function. The wave function is not influenced by the particle and can exist also as an empty wave function.

The theory has nonlocality, which makes it compatible with Bell's theorem.

Sure we can now still argue about 'nonlocality'.

DavidL,

"The one defining property that we know it must then have from every experiment that has ever been done is that each and every observer must somehow drag with him both his local Aether, and the Aether through which any of his experimental photons have traveled."

I don't get very well what you are saying here, but if you have bubbles of air rising in water and consider them as a particle, than they aren't dragging along the water around them but surely you could measure the vibrations they make when traveling through the water.

"And how has your billion year old universe been expanding into the Aether without any changes in form? What is causing it to expand when gravity should be continuously pulling it together?"

I'm not saying that the Aether is Expanding, all I said is that we are expanding in the Aether with our 'Little Bang' the day the Milky Way was born out of a cloud of cosmic dust, and Stars start to shine.

And Gravity has created this giant structure in the Universe with Canals, where gravity adds up, so no not everything isn't collapsing, there is a construction.

"but if you have bubbles of air rising in water and consider them as a particle"

Why is that really the case?

"where gxravity adds up,"

So wherever there isn't antigravity...

"so no not everything isn’t collapsing, there is a construction."

No, the construction of blobs of gas is because they're collapsing.

Idiot.

Hey how about this:

If you imagine particles as being ballerinas dancing on stage, then there must be a really small tutu in the universe.

“but if you have bubbles of air rising in water and consider them as a particle”

HANG ON! Water and air are MADE OF PARTICLES.

If you consider air and water particles, then electrons, which are particles, are made of air, which contains electrons, neutrons and protons. Which are made up of air, ...

Your idea is insane!!!

Wow,

Hold your horses, the reference was only in relation to how something travels through a medium and the drag it has. Let's wait for 'DavidL' to better explain what he meant with :"The one defining property that we know it must then have from every experiment that has ever been done ..."

Huh, you think that water and air don't exist now???

chelle
September 13, 5:53 am
...
For instance, you can use as a metaphor for SpaceTime a trampoline with a rock in the middle; and an amount of water also on it, that might be in total more massive than the rock, but as a result of weak bonding the water will flow towards the rock.

Wow
September 13, 6:25 am

Of course, there’s no reason for any water in this analogy.

Chelle
September 13, 7:19 am

What else are stars and planets than condensed matter, just like a cloud of lose molecules that bond into water, or any other condensed liquid gas

(so no, you don't get to pretend your metaphorical water and air are metaphorical and not metaphorical when you wish)

"explain what he meant with :“The one defining property that we know it must then have from every experiment that has ever been done …”"

Can you explain what properties your aether has, or is your confusion here that you think eiher the aether has NO properties, or that those properties change at a whim?

Chelle (much earlier):

when you pull on a feather or any other rigid body, you pull the whole feather along because it is chemically bonded in a stronger way than a ‘cloud’ of particles.

If you understand how the EM force can overwhelm an opposing gravitational force, then why don't you understand how a gravitational force can overwhelm the expansion? The analogy to a rigid body might not be great but you seem to grasp the general solution here; just apply the lesson you've learned from 'what happens when the EM force is locally stronger than gravity' to 'what happens when gravity is locally stronger than the expansion.' The feather stays together. At least temporarily.

eric,

I have no problem with the fact that gravity would be locally stronger than the Expansion, keeping things together. This was also part of my motivation that Expansion isn't working, because on a 'global' scale gravity is holding that Giant Structure together, while on a 'small' scale gravity keeps the Milky Way together, both are 'rigid' structures, countering Expansion. The argument about the feather started about the fact that within the 'canals' cosmic dust clouds with a 'weak' gravitational bonding structure, reform themselves into tight (rigid) points: Stars and galaxies; so that giant structure keeps on 'refreshing' its composure and keeps on being tightly bonded, and thus countering the Expansion.

Wow,

"Can you explain what properties your aether has"

For now that's the secret recipe that the chef is working on. :mrgreen:

So "no" is the answer.

Wow, why don't you first take your time to digest the idea that there is an Aether, when this has happened, we can start to talk about the properties of Aether that's being digested by the particles that move through it.

I have digested the idea there could be an aether. However, the result is that the idea is ridiculous.

David will not be clarifying his question because I've asked you what he said and you gave an avoiding nonanswer because you don't know what the hell you're on about.

You have refused to answer what properties the aether has beause you don't have a frigging clue.

As with so many other things in life.

And if you're pretending to write a paper and that's why you're not telling anyone what the properties of your aether are, then why the hell are you asking other people to work it out for you?

As Wow says, this is probably futile but here goes anyway. I see no need to "adjust [my] existing Muscle memory that says that there is NO Aether." because the difference between "there is no Aether" and "there is an Aether but it has no observable effect on our universe" is one of semantics not science. One is shorthand for the other.

However, your existing "Muscle memory" seems to be locked onto the idea that there must be an Aether just as some people know that there must not only be a God, but He must be their exact God. All evidence to the contrary must be somehow explained away however ludicrous those explanations have to become. You seem to genuinely believe that if even a few of the world's astrophysicists had half your insight we would have found the Aether by now. If you cannot specify the expected properties of your Aether you can never find it. Pauli was reputedly embarrassed at postulating the neutrino because he thought it could never be seen, but unlike your Aether it was at least needed to make equations balance. and its properties well enough define to allow its presence to be detected as technology advanced .

I will repeat again Every measurement that has ever been done shows the speed of light if the same in every direction regardless of the direction of travel through any Aether. Not only has this been verified to very high precision, it is the central tenet of Einstein's Theory of Relativity. There must be hundreds of millions of GPS receivers built to thousands of designs sold around the world. Not one, even those used for military applications and precision low-bandwidth seismic monitoring, has ever claimed to give more accuracy by determining which way the receiver and/or the satellites are moving through the Aether.

If you think the universe of 1 billion years ago looked much as now, how far do we have to go back before it was different? How did it look when it started and how long ago was it?

Incidentally despite your incredulity at the idea of there being no Aether, I personally find the idea that "space" as we perceive it in our universe is some sort of emergent property of the "stuff" in it causes less incredulity on my part than your concept of an infinite array of pre-existing empty "space" into which your (over 1 billion year old) fixed universe is radiating energy and gravity. Like your comments here, this particular statement is one of personal gut feeling based on no science whatsoever.

Chelle:

I have no problem with the fact that gravity would be locally stronger than the Expansion, keeping things together. This was also part of my motivation that Expansion isn’t working,

But you agree that gravity works on the feather, right? It doesn't 'stop working' just because the EM force is holding the feather together. One force does not stop the other force from working, it just counteracts the effect you might otherwise see. The bottom of the feather does not fall if you are holding the top, but we still say that gravity is working on the feather.

Apply that lesson here. The space in which two gravitationally bound objects expands. The fact that they do not move apart does not imply that the expansion "isnt' working." It just means the force of gravity holding them together is stronger than the expansive force pushing them apart - but the expansive force is still there, stil working, the same way gravity is still there working on the bottom of the feather, even if it doesn't fall.

eric,

I agree with what you are saying, but the problem is that Expansion is going equally accordingly to the Redshift measurements, and Hubble constant, in all directions (x,y,z). But if you have a construction made out of Gravity, that works against the Expansion and which is a rigid framework, than the Stars can no longer be equally moving away from each other in all directions (x,y,z). Look at this image and compare A with B:
http://tinyurl.com/Canal-Structure-Expansion

For A there is no gravity connection between those 2 points, while for B there is a strong connection. So it can't be that they all are moving away at the same speed from each other, and certainly not away from us, all in the same direction, away from us. So either Gravity has no influence and than the Milky Way is expanding into pieces, or it has influence, and than the Expansion can not cause Stars to move Equally away from each other, and AFAIK the Milky Way is bounded together.

"but the problem is that Expansion is going equally accordingly to the Redshift measurements, and Hubble constant, in all directions (x,y,z)"

Yes, it is. This is not a problem unless you demand that there be an aether.

Which is what YOU mean when you say "the problem is...". It's not a problem with the science, it's YOUR problem with the science.

"the Expansion can not cause Stars to move Equally away from each other"

Why?

"But if you have a construction made out of Gravity"

And if you don't have a construction made out of gravity, your "problem" no longer exists.

"One force does not stop the other force from working, it just counteracts the effect you might otherwise see"

No it doesn't.

If you push my car one way so hard and I push it the other way harder, the car doesn't stay still.

"For A there is no gravity connection between those 2 points"

Yes there is.

"while for B there is a strong connection"

Calculate the strength of connection.

"So it can’t be that they all are moving away at the same speed from each other"

They aren't.

"and AFAIK the Milky Way is bounded together."

You don't know jack:

boundedpast participle, past tense of bound (Verb)
Verb:

Walk or run with leaping strides: "Louis came bounding down the stairs".
Form the boundary of; enclose: "the ground was bounded by a main road on one side and a meadow on the other".

DavidL,

the difference between “there is no Aether” and “there is an Aether but it has no observable effect on our universe” is one of semantics not science.

You are twisting a few words around here, it has observable effects, such as Wave-Particle duality, to have a wave you need to be a medium, but the issue is how to measure it. You can measure Gravity, but you could also see it as an effect of the Aether, that's how Einstein saw General Relativity as a new introduction of the Aether after he left it out in Special Relativity.

You seem to genuinely believe that if even a few of the world’s astrophysicists had half your insight we would have found the Aether by now. If you cannot specify the expected properties of your Aether you can never find it.

We haven't had the CFD tools up until now, and you also have the issue of people like you, Wow and others that have been thought at school that Aether does NOT Exist, which is a misconception as I've tried to show you over and over again. Lorenz and Einstein where no dumbasses, and if you know your history, than the fight was mainly against Heinrich Hertz his kind of Aether.

btw you also need to look at the political issue, and here I bring up your friend Pauli, he was part of the Copenhagen group that heavily campaigned in favor of it its own 'interpretation', as many things in history the story of those who lose isn't mentioned in schoolbooks such as that of Louis de Broglie. It is known that Pauli was a bit of a bully just like 'Wow' that hangs around on this forum, Wolfgang Pauli even put Ralph Kronig down when he proposed 'Spin', anyway read this:

From this idea, de Broglie developed the Pilot Wave theory, and worked out a function for the guiding wave. Initially, de Broglie proposed a double solution approach, in which the quantum object consists of a physical wave (u-wave) in real space which has a spherical singular region that gives rise to particle-like behavior; in this initial form of his theory he did not have to postulate the existence of a quantum particle. He later formulated it as a theory in which a particle is accompanied by a pilot wave. He presented the Pilot Wave theory at the 1927 Solvay Conference. However, Wolfgang Pauli raised an objection to it at the conference, saying that it did not deal properly with the case of inelastic scattering. De Broglie was not able to find a response to this objection, and he and Born abandoned the pilot-wave approach. Unlike David Bohm, de Broglie did not complete his theory to encompass the many-particle case.

Later, in 1932, John von Neumann published a paper claiming to prove that all hidden variable theories were impossible.
http://en.wikipedia.org/wiki/Pilot_wave

If you think the universe of 1 billion years ago looked much as now, how far do we have to go back before it was different? How did it look when it started and how long ago was it?

How would I know, this is way beyond our grasp. I only know for sure that we as Solar System in a Galaxy where one day born and that we are expanding at the speed of light further into to space, and that this is expanding influence is the most logic cause for Redshift. If you blow with a propellor harder and harder in the direction of a sound source than it will also look as if that speaker is moving further and further away, certainly when it is omni-directional and everything is moving away at the same speed.

Like your comments here, this particular statement is one of personal gut feeling based on no science whatsoever.

No it is not particularly about a 'gut feeling' rather a rational look at how things can work how they can't work if there is no Aether in reality.

Wow,

Have you lost your mind? You just made 8 comments to my one reply to eric. Can't you control yourself just a little bit?

"You are twisting a few words around here, it has observable effects, such as Wave-Particle duality"

How does aether do that?

chelle, I'm trying to make comments that are small enough to fit into the tiny itsy bitsy gap you let anything in to that dense object you call "my brain".

Obviously, you need smaller chunks.

"only know for sure that we as Solar System in a Galaxy where one day born and that we are expanding at the speed of light further into to space"

An example of how you know for sure a load of crap.

HINT: WRONG!!!

"We haven’t had the CFD tools up until now"

CFD doesn't give you wave particle duality.

"If you blow with a propellor harder and harder in the direction of a sound source than it will also look as if that speaker is moving further and further away"

No you won't.

"certainly when it is omni-directional and everything is moving away at the same speed."

Are you saying that the universe is expanding isotropically now???

"that have been thought at school that Aether does NOT Exist, which is a misconception"

You mean "Sanity", right?

"as I’ve tried to show you over and over again"

By "show" you mean "repeatedly with no evidence or even coherent sentence", right?

"Lorenz and Einstein where no dumbasses, and if you know your history"

... you'd know that Einstein said there is no Aether.

"to have a wave you need to be a medium"

Which is PRECISELY why 18t hcentury scientists thought there was an aether.

However, in the 20th century we found that that statement was FALSE.

"How would I know, this is way beyond our grasp."

Yours.

Not everyone's.

“to have a wave you need to be a medium”

So we need to speak with the dead before you can wave???

Chelle, every atom of your body is attracted to every atom of mine.

I'm not hitting on you, it is just an inescapable consequence of the Law of Gravity. It applies if we are standing next to each other, on opposite sides of the world, or at opposite ends of your Arrow B or your Arrow A. Why do you think there are regions in space where this law is violated?

"How would I know, this is way beyond our grasp." Beyond yours, but the standard model comes up with a pretty good estimate. And of course you have no problem stating what the universe looked like a billion years ago. Why is it so difficult to go back any further?

DavidL,

"Why do you think there are regions in space where this law is violated?"

Yes of course there is a gravity connection between those 2 points in the case of A, I expressed myself badly. What I should have said is very weakly. But you see in those canals gravity adds up, while over the wide open space there is no (or I should say very little) mass that maintains a connection while it is the case within those canals; linked vs. (almost) unlinked.

" ... the standard model comes up with a pretty good estimate."

I guess you mean here the 'Big Bang' model, because The Standard Model (of particle physics) is something else. If you and your friends such as 'Wow' like to take the Big Bang as the reference for the evolution of the Universe, than you can do as you wish, just like I'm not holding you back from believing in any other well calculated fairy tale. You may keep on living in oblivion, for me the expansion of our own little universe (Solar system/Milky Way) in the giant Aether bath that the real Universe is, is more sensible. Anyway, it's a free world, have fun!

chelle, think of your comments as a huge lake of semiliquid sewerage and your statements solid turds in that sewerage. Then my comments have been me taking out each little brown Richard-the-Third and pointing out to you "Have a look at this".

Consider each one a turd you can, individually, and without pressure on selection of any particular one, point out the feature of that single lump that indicates it is not, in fact a piece of shit.

Apparently not even you wish to acknowledge or rebut each little piece of crap dredged out of your slurry of words.

"Yes of course there is a gravity connection between those 2 points in the case of A, I expressed myself badly"

So when you say something completely apparent and wrong, this isn't you being wrong or lying, it's you "expressing yourself badly"????

Tell me, have you EVER owned a dictionary?

"But you see in those canals gravity adds up"

It adds up EVERYWHERE.

"I guess you mean here the ‘Big Bang’ model, because The Standard Model (of particle physics) is something else"

It is something else, but no, the BB model relies upon the SM.

"just like I’m not holding you back from believing in any other well calculated fairy tale."

Unlike the incalculably excrebale fairy tale of the Aether.

"in the giant Aether bath that the real Universe is, is more sensible."

Far more stupid, you mean. You're "expressing yourself badly" (i.e. lying your arse off) again.

"Anyway, it’s a free world"

However, the world is not free to acknowledge the aether DOES NOT EXIST and moreover have to put up with your whining whinging and bitching laced withing semiliterate prose, inarticulate sentences, laced with bad analogies that morph within the same sentence and segued into something that doesn't follow until the cows die of malnutrition.

Not very free, is it.

... semiliterate prose, inarticulate sentences, laced with bad analogies that morph within the same sentence and segued into something that doesn’t follow ...

My mind is structured in such a way that it can easily position objects moving round and through space, but when having to put those thoughts in a simple flat straight linear line from left to right, what writing is, than I'm having difficulty to let those spacial dimensions go, and things become messy. Since the day I started learning to write I had this issue, sorry for my bad spelling.

Chelle, it is not a question of believing. I am an Engineer not a Scientist, and as long as photons reliably behave like waves when I try to detect their diffraction paterns, and particles when I try to count them, what they actually are is irrelevant. As long as the appropriate analogy accurately predicts their behaviour, and does so regardless of which way they are moving through any Aether, then.any paradox only seems to result from the failure of your extrapolated metaphor to describe reality. You therefore conclude it is reality that has a problem!

From your previous posts you seem happy to accept a fixed universe where gravity somehow manages to constrain matter within an array of "knots" connected by "canals" Odd indeed that you are postulating that the only place in the universe where there is any expansion* is in our tiny insignificant galaxy that is but a small subset of our "knot". The one region where we know for certain that gravity has been winning for the last 4.5 billion years at least, and where speeds can be inferred from distances measured by parallax without any knowledge of redshift. See the problem here?

*Expansion used in your sense : objects moving apart in a fixed space.

My mind is structured in such a way that it can easily position objects moving round and through space

However, it really seems to struggle with a universe that does not conform to your idea of a fixed 3-dimensional grid.

"My mind is structured in such a way that it can easily position objects moving round and through space"

Then why do you fail to take advantage of it?

"but when having to put those thoughts in a simple flat straight linear line from left to right"

Who is doing that?

"what writing is"

It includes writing a coherent sentence in the language you're conversing in. Your brain doesn't seem to do that.

DavidL,

"I am an Engineer ... what they actually are is irrelevant."

Of course that's your job as an engineer, to apply the math and that's it. If you want to measure how fast a car is driving, you only need a few measurements and you can figure out a lot of things, there is no need to bring the actual car into the picture, it all works on paper.

"Odd indeed that you are postulating that the only place in the universe where there is any expansion (objects moving apart in a fixed space) is in our tiny insignificant galaxy that is but a small subset of our “knot”."

I'm not postulating that there is an 'expansion' only in our Milky Way.

First of all the Milky Way is not expanding, because gravity is keeping it together, this is something we all agree upon. Second, when I say that we (Solar system/Milky Way) are expanding in to Space, than I'm speaking about the light we emit, and the gravity that stretches out into space. See it as putting a heating element in the middle of a swimming pool, the longer you have it emitting heat, the wider the pool gets to be warmed, affecting incoming light. So the heating element isn't expanding but it's 'influence' within the medium is expanding. Now incoming light would start to show some scattering effects, but something like a torpedo (wave-particle) would keep it's straight line towards the heating element, but have a different property than when the water would have had a constant non gradient temperature level.

"than I’m having difficulty to let those spacial dimensions go"

Go where?

"Since the day I started learning to write I had this issue"

So you stopped learning how to write?

"Of course that’s your job as an engineer, to apply the math and that’s it"

Incorrect. He applies science to the world around him to change it.

If he uses talcum powder because he thinks it is highly gravitationally repulsive hence will suspend above the earth easier and would make a good suspension bridge, he will have evidence of his failure in front of him.

"but something like a torpedo (wave-particle)"

A torpedo is a particle. Not ever a wave.

"would keep it’s straight line towards the heating element"

Torpedos don't go towards heating elements.

"but have a different property than when the water would have had a constant non gradient temperature level"

What different property? Torpedos don't change into bunnies when below the thermohaline incline.

You don't know about torpedos or the ocean, do you.

"and you can figure out a lot of things"

Whereas you still haven't figured out a thing.

"when I say that we (Solar system/Milky Way) are expanding in to Space, than I’m speaking about the light we emit"

The expansion of the universe isn't expansion of the light emitted by objects in that universe.

"See it as putting a heating element in the middle of a swimming pool"

No.

See it as a lightbulb emitting radiation. But that doesn't mean someone is saying the lightbulb is expanding into space.

"the wider the pool gets to be warmed"

You don't know about water either, do you. Or pools.

Wow,

Your small comments around my posts are starting to look a bunch of pubic hair around ...

Well you are one, aren't you.

I guess you still refuse to clarify any single point, do you. I guess that's because you have to hide your "little gems of brown knowledge" in a huge pool of opaque slurry, lest people recognise its character.

Go on, counter a point or respond to one statement. Show that you can cohere to at least ONE statement.

Or are you intellectually incapable?

Or are the small comments too big for you to mentally digest?

Too dumb to find an answer?

Come on, you were quick enough with the "observation" about your posts being that piece surrounded by hair...

"I’m not postulating that there is an ‘expansion’ only in our Milky Way."

"First of all the Milky Way is not expanding,"

Perhaps we are getting somewhere at last. It helps if we speak the same language. When you say that our galaxy is expanding, you simply mean it is broadcasting its presence to the rest of the universe. Perhaps you should pick a less ambiguous word, but I'm okay with that concept. and also that we can observe the rest of the universe broadcasting in a similar manner.

So do you think there is any real expansion(i.e physical objects getting further apart) going on and if so where and why when gravity should prevent it?

Can you explain the source of the redshifts we observe (light wavelength apparently increasing, not simply getting dimmer) and its apparent correlation with the distance of the light source from us?

DavidL,

you simply mean it is broadcasting its presence to the rest of the universe.

Yes.

For the rest you can look at the Universe as one giant static aquarium (Aether), with canals of gravity in them, where clusters move in all directions. And the longer we 'broadcast our presence' in the aquarium, the more we heat up the water around us, so light that comes from further away and gradually get's to be 'hit' earlier and earlier by our 'field', and so it starts to shift more and more over time, we aren't a static entity. You also have to remember that there once was a day that we weren't born and emitting light.

btw how fast would a signal be 'traveling' from one side of the Universe to the other, through those canals, thanks the gravitational tension in that web-construction, just like how a spider reacts and catches it's pray when a web-wire is only slightly triggered: http://www.bbc.co.uk/nature/18990161

Wow,

I would love to continue to debate with you, but you are very biased and you are sticking to your guns such as 'there is No Aether', and the 'speed of light is constant'. If you want to evolve than you also need to dare to challenge some existing knowledge.

"I would love to continue to debate with you, but you are very biased and you are sticking to your guns such as ‘there is No Aether’, and the ‘speed of light is constant’. If you want to evolve than you also need to dare to challenge some existing knowledge."

Maybe take some of your own advice and apply it to yourself.
It's not a problem of what you believe in. It's the problem of you pretending it's some form of science. You haven't provided any evidence for any of it. Thus, that makes it pseudo science. You don't like it. Fine, provide scientific proof. Until that day you are nothing more than a charlatan.

Let's do this small steps at a time to see where we are agreed. Firstly regarding your comment to Wow, can we agree that "the speed of light has never been observed to be affected by the Aether"?

So, a couple of simple questions.

Do you think there is something special about your canals such that gravity within them is fundamentally different to gravity between them?

Are you trying to say that you think redshift is due to photons coming to us interacting with those we are radiating out?

"For the rest you can look at the Universe as one giant static aquarium (Aether)"

Which is presupposing your answer.

"Imagine there's an Aether, then the aether exists!".

Vapid idiocy as normal.

"with canals of gravity in them"

Gravity doesn't form canals. It radiates isotropically.

"where clusters move in all directions"

If you have them in canals, they don't move in all directions.

"so light that comes from further away and gradually get’s to be ‘hit’ earlier and earlier by our ‘field’"

Light doesn't hit light.

"and so it starts to shift more and more over time"

No it doesn't.

"we aren’t a static entity."

Non sequitor.

"You also have to remember that there once was a day that we weren’t born and emitting light."

Irrelevant.

"btw how fast would a signal be ‘traveling’ from one side of the Universe to the other, through those canals"

Since there are no canals formed of gravity, doesn't exist to answer.

"thanks the gravitational tension in that web-construction"

There is no gravitational tension. Gravity isn't formed into canals.

"just like how a spider reacts and catches it’s pray when a web-wire is only slightly triggered: "

Where did a space spider come from?

"I would love to continue to debate with you"

No you wouldn't

"but you are very biased"

Yeah, I'm pretty biased to answers that mean something. Mean old me.

"and you are sticking to your guns such as ‘there is No Aether’"

There is also no Heffalump, no Great Green Arkleseizure and no Tooth Fairy.

Ever considered there isn't an Aether?

"If you want to evolve "

Evolution happens to the progeny of species. It doesn't happen by thinking really hard.

"you also need to dare to challenge some existing knowledge."

I do. But you insist that this is biased and therefore cannot be considered.

"Are you trying to say that you think redshift is due to photons coming to us interacting with those we are radiating out?"

I'll answer since chelle will respond with verbal diarrhoea.

Yes.

"can we agree that “the speed of light has never been observed to be affected by the Aether”?"

Yes, but not in reverse, the state of the Aether could affect the speed of light, e.g. Red Shift.

"Do you think there is something special about your canals such that gravity within them is fundamentally different to gravity between them?"

Of course, that's what I have been saying all the time, look at my comment on September 12, 5:09 am. Gravity itself is the same surely, but putting elements in a line causes them to add up. See, A pulls on B, B pulls on C, so when A pulls on B it also pulls on C. It's about connectivity. But not only does A pull on B, A also pulls on C, and etc. ... this way you establish a strong connection just like the wire of that spider. Or when you put one layer of epoxy over the other, it all adds up and strength increases, making very tense canals, and structures.

"Are you trying to say that you think redshift is due to photons coming to us interacting with those we are radiating out?"

Yes but not in the sense of the old Tired Light hypothesis. Light that moves through the Aether, sucks energy out of the Aether, so the tension within the Aether becomes slightly smaller and thus light moves slightly slower and loses some energy. So on Earth we all are bathing in the same Aether temperature and light is constant, but if you go very far in to space you get a small difference.

Sinisa,

History has thought us that, it are always small adjustments of, or better small additions to, an existing theory that gave us a better understanding. I'm not adding very spectacular things here.

"Yes, but not in reverse"

What IS the reverse?

"the state of the Aether could affect the speed of light, e.g. Red Shift."

So could the wings of invisible pink unicorns.

If they existed.

What, pray, is the method by which this mystical process occurs and how does it manage to move in every single direction all at the same time?

"Gravity itself is the same surely"

The source of your ineducated spiel.

Why do you think it surely is? Because you feel it must.

"but putting elements in a line causes them to add up"

Their existence causes the gravitational attraction from each to add up.

"See, A pulls on B, B pulls on C, so when A pulls on B it also pulls on C."

Doesn't.

A pulls on B and C. C pulls on A and B. B pulls on A and C.

"this way you establish a strong connection just like the wire of that spider."

Except there is no web.

"Or when you put one layer of epoxy over the other, it all adds up and strength increases"

It doesn't. Indeed, it likely gets weaker unless the epoxy is stronger than the binding it has to the material or the material itself.

"Light that moves through the Aether, sucks energy out of the Aether"

No it doesn't.

"so the tension within the Aether becomes slightly smaller and thus light moves slightly slower and loses some energy"

If light sucks energy out of the aether (it doesn't) then it gains energy not loses it.

"I’m not adding very spectacular things here."

You're adding nothing other than noise, signifying nothing.

"History has thought us that, it are always small adjustments of, or better small additions to, an existing theory that gave us a better understanding."

This is true, but has no bearing on what I posted nor what you posted.

"I’m not adding very spectacular things here."
You are adding VERY spectacular things. i.e. speed of light not constant, gravity not propagating same everywhere, existence of some underlying medium etc.. etc.. Those are all spectacular claims.

But, you are in a way correct that you are not adding anything to the existing physics, since you offer nothing scientific, no equation, no observation, nothing that distinguishes science from religion. Thus my comment stands, what you do is pseudo-science and charlatanism.

“so the tension within the Aether becomes slightly smaller and thus light moves slightly slower and loses some energy”

If light sucks energy out of the aether (it doesn’t) then it gains energy not loses it.

No, it is the overall tension in the Aether that drops. Imagine planting a bunch of threes who all cast a shadow, than the ground temperature drops. It is also how gravity works like 'david' repeated what Galileo said: "eppur si muove", to generate gravity you need to have your particles moving. The tension of the Aether always moves towards; the shade of the particle/low pressure/empty container. To keep it's empty spot it needs to keep on moving forward, to keep it's shade. Just like Hilbert's paradox of the Grand Hotel, or how a horse chases a carrot:

http://youtu.be/-PVFBGN_zoM

The particle needs to keep on rolling forward to maintain it's empty space.

"No, it is the overall tension in the Aether that drops."

Which says nothing to contradict that the photon that takes energy out of the aether would gain energy, not lose it.

"Yes, but not in reverse, the state of the Aether could affect the speed of light, e.g. Red Shift."

Chelle, a response to my original question is worthless without yes/no answer. Let me amend it to “can we agree that “the speed of light has never been observed to be affected by the Aether, and the state of the Aether has never been observed, period.”?

If you can't answer "yes" to that, please tell us exactly what has been "observed", and as the rest of your post reads like a New-age woo merchant's pseudo-scientific justification for the latest quack medicine, please restrict your explanation to mostly established science so that we are only required to make "a small adjustment" to existing Theory.

"Imagine planting a bunch of threes who all cast a shadow"

No need. I've done that.

It looks nothing like photons and aether.

"than the ground temperature drops."

This is because there is less light falling. The photons don't lose energy, they warm something else up instead.

"It is also how gravity works"

Nope, trees creating shadow isn't how gravity works. Even in a total eclipse of the Sun, we still feel the gravitational pull of the sun just exactly as hard as when there's a lunar eclipse.

"The tension of the Aether always moves towards"

You need to finish your.

"the shade of the particle/low pressure/empty container"

There is none.

"Just like Hilbert’s paradox of the Grand Hotel"

There is no infinity in reality.

"The particle needs to keep on rolling forward to maintain it’s empty space"

The particle has no empty space to maintain. Atoms retain their empty space between the electrons and the nucleus when stationary.

"to generate gravity you need to have your particles moving."

No you don't.

All you need is mass.

DavidL,

Yes.

Could you imagine a universe where the threshold would be lower, so the Aether would more heavily influence how photons move through the Aether.

btw since when is fluid dynamics a 'New Age' thing?

"btw since when is fluid dynamics a ‘New Age’ thing?"

Never.

Neither are crystals nor energy a new thing.

However, the New Age Bollocks misuse both to peddle their idiocies.

"Could you imagine a universe where the threshold would be lower, so the Aether would more heavily influence how photons move through the Aether."

No.

Because you haven't explained the properties and mechanism of the aether to anything near what is required.

There's also no indication of how this influence would change anything or make something explicable.

Excellent Chelle we have agreement. That understanding that "The speed of light has never been observed to be affected by the Aether, and the state of the Aether has never been observed, period." is now central to future debate.

“Could you imagine a universe where the threshold would be lower,"

Absolutely. This could probably happen close to a plane in the Aether where a thin layer of Kryptonite was sandwiched between two graphene films, but investigation of this hypothesis must wait until we find an area of space radiating light showing the strong lines of the absorption spectrum of Kryptonite.

In the mean time, can you explain the redshifts we measure in terms of things we have observed?

DavidL,

In the mean time, can you explain the redshifts we measure in terms of things we have observed?

Can you prove me the Expansion of Space besides using the Red Shift that I could equally use to prove the Existence of the Aether.

"that I could equally use to prove the Existence of the Aether."

Since this is what David is asking you to do, you're both in agreement that you should do it!

Additionally, since you agreed that the aether hasn't been seen to affect light, go ahead, chelle, prove the existence of aether with redshifts that aren't affected by the aether.

Not going to? Unable? Working on it? What?

Meanwhile, the expansion of the universe and the redshift are explained by NORMAL science (as opposed to post-normal or ab-normal) with something called "The Doppler Shift" and is the result of ANY wave emitted from a source moving in relation to an observer.

You can even check it out yourself in everyday life.

Unlike the invisible pink unicorn, sorry, aether.

"Can you prove me the Expansion of Space besides using the Red Shift that I could equally use to prove the Existence of the Aether."

I am not in the business of proving anything, nor is any Scientist. Only mathematicians do that. Scientists try to explain observed phenomena, and make predictions based on their acquired understanding. I am not asking you to prove anything either, merely to explain the red shift. My explanation is that the red-shifted objects appear to be moving away from us. This does not require expanding space. By regarding the Big Bang as a huge conventional explosion hurling galaxies through the Aether, the Doppler effect will generate a red shift as well: indeed I suspect that 95% of people who are aware of the concept of the Big Bang would explain it this way if asked. If this was your hypothesis, we could pursue how to distinguish between the two possibilities. But your static universe precludes this mechanism, so the next step is to examine your explanation for the red shift to see if it we can fit it into known physics with only small changes

Except the aether, being the medium of transfer for this hypothesised light is moving too. Which means that if it were a conventional explosion, we would be able to tell who is at the center of the universe because only those still at the centre see retreating aether in every direction.

Anyone NOT at the center and unmoving from it would see anisotropy as aether "nearer" the point of explosion coming toward them faster than the aether further from the explosion is going away.

Either our planet on the edge of the milky way "happens" to be at the single point at the exact centre of the big bang (why did the rest of the milky way get shafted on this special position? And what happens as we rotate around the Milky way? We'd no longer be AT the centre, so it would be a double cooncidence that we happen to be at this point ONLY when we're able to note it), or there is no aether.

DavidL,

I am not asking you to prove anything either, merely to explain the red shift.

I already did so in my comment at 2:26 am:

First of all the Milky Way is not expanding, because gravity is keeping it together, this is something we all agree upon. Second, when I say that we (Solar system/Milky Way) are expanding in to Space, than I’m speaking about the light we emit, and the gravity that stretches out into space. See it as putting a heating element in the middle of a swimming pool, the longer you have it emitting heat, the wider the pool gets to be warmed, affecting incoming light. So the heating element isn’t expanding but it’s ‘influence’ within the medium is expanding. Now incoming light would start to show some scattering effects, but something like a torpedo (wave-particle) would keep it’s straight line towards the heating element, but have a different property than when the water would have had a constant non gradient temperature level.

By regarding the Big Bang as a huge conventional explosion hurling galaxies through the Aether ....

The 'proposed' Big Bang doesn't work like that, it isn't like a fire cracker ...

here's a video: http://youtu.be/i1UC6HpxY28

the next step is to examine your explanation for the red shift to see if it we can fit it into known physics with only small changes ...

I don't know what's going on, but I've been explaining all this in many comments now; the excitement of the Aether gradually changes, over distance, over the time that we have been sending out energy, light and gravity into Space, since our galaxy and solar system was born. So the 'only small change' you need to embed into the program is an expanding temperature (excitement) gradient of the Aether around us, that's it.

"I already did so in my comment at 2:26 am:"

Which bit?

"See it as putting a heating element in the middle of a swimming pool"

No.

Because it isn't.

"incoming light would start to show some scattering effects,"

Which isn't seen. Ergo aether doesn't exist.

"but something like a torpedo (wave-particle)"

Torpedos aren't wave-particles. They're torpedos. Entierly and to all calculable limits solely and irrecovably particles.

Which light isn't

"but have a different property than when the water would have had a constant non gradient temperature level."

Torpedos don't act that way.

"The ‘proposed’ Big Bang doesn’t work like that"

We know.

David was trying to find out what the hell you're talking about.

"the excitement of the Aether gradually changes"

What excitement?

"over distance"

So it is moving????

"over the time that we have been sending out energy"

We haven't been here for most of the universe. What happened before then?

"since our galaxy and solar system was born"

Why only then?

"an expanding temperature (excitement) "

That isn't what excitement is. Do you know what temperature IS?

At all?

"gradient of the Aether around us, that’s it."

What on earth does THAT do???

So to recap as to what chelle has agreed is factually supported by any evidence:

1) The speed of light is NOT affected by the aether

2) filament structures CAN be replicated from gravitational attraction and universal expansion together

Wow,

So to recap as to what chelle has agreed is …

Great, so now you're not only filling this whole comment section with your filibustering posts, but you are also drawing false conclusions and making false suggestions. You are crossing a line here Wow, there is definitely something wrong with you.

What false conclusions?
#1 you agreed in the post at 8:03 on this thread.
#2 you agreed to in the post at1:10 pm on the "earth is moving" thread.

We already know there's a whole passel of things wrong with you.

This latest aneurism is no surprise any more.

And where are these "false suggestions"?

Are you even on the same planet as the rest of reality???

Wow, you are something else, for sure.

Anyway I'm going to follow up CB's advice and stop feeding you.

Salu2

Chelle:

For A there is no gravity connection between those 2 points, while for B there is a strong connection. So it can’t be that they all are moving away at the same speed from each other, and certainly not away from us, all in the same direction, away from us.

Ah, I think I get what you're saying now. Your mistake is thinking that the statement "objects move away from us faster, the further away they are" is an ironclad rule that all objects follow, rather than a general trend.
You are right: if every single object obeyed Hubble's law with equal and high precision, that would mean that gravity is having no effect. But they don't. Take a look at the Wikipedia page for Hubble's law. See the graph about 25% down the page, on the right? You'll notice that not all the points fall on the line. In fact, very few of them fall exactly on the line. The differences are due to gravity.

Now granted, this is a relatively simple and small data set, but the argument above holds for more comprehensive data sets too. We do not observe every single object obeying Hubble's law with equal and high precision. The difference between the line and the points are generally due to gravity (though, since IANA cosmologist, I will hedge and say there may be other effects I don't know about).

***

To Wow - serioulsy man, can you quit with the one-liners? If you have ten things to say about one of Chelle's responses, do us ALL a favor and don't hit send after each one. Collect them in a single message. You are filling the thread.

Eric,

"Ah, I think I get what you’re saying now. Your mistake is thinking that the statement “objects move away from us faster, the further away they are” is an ironclad rule that all objects follow, rather than a general trend."

Don't know if that's 'my' mistake, on a local scale this is the case because gravity does hold things together.

No, my real giant mistake was using that image to start with. I thought that it was in analog with the exact position of the Stars, as Ethan talked about the 'Giant Superstructures in our Universe'. If someone had pointed out that it wasn't a real image based on the distance of all the stars around us, than I wouldn't have made a fool out of myself. So there are no such structures in Space, or are there?

So what are those millennium images actually showing; contractions of matter (gravity) with an additional 'constant' force of expansion … but than again you say that according to real measurements it is rather 'a general trend' than a 'rule'. So how fair are those simulations, when you set for everything the same Z, what my first point of argumentation was during this debate, and so what are they actually showing us that is real?

"You are filling the thread."

This is the point, eric.

"Don’t know if that’s ‘my’ mistake"

It is.

"stop feeding you."

If you mean "stop answering my questions, you never started.

" Ethan talked about the ‘Giant Superstructures in our Universe’."

Just like people talk about swirls in the fog.

Do you go all apeshit over those destriptions?

"than I wouldn’t have made a fool out of myself."

The evidence indicates otherwise.

"contractions of matter (gravity) with an additional ‘constant’ force of expansion"

Just the density fluctuations of matter. Nothing else.

"but than again you say that according to real measurements it is rather ‘a general trend’ than a ‘rule’."

Nope, he doesn't say that.

Read it again.

"when you set for everything the same Z"

They aren't.

Yet again you fail to read anything given to you.

Z is not the same value for all things in the universe.

"what my first point of argumentation was during this debate"

Yes, what WAS your first point of argumentation?

You sentence need some things.

eric,

I have one additional question; how do you embed this Expansion rate Z into the simulation program? For Expanding Space to pull the matter within it along, that overrules Gravity, that space needs to apply an attraction force on matter to pull it along, otherwise 'Space' is just flying by, or does each piece of matter has a 'given' expansion *factor* within itself?

"how do you embed this Expansion rate Z into the simulation program"

It's already been answered. And displayed.

"or does each piece of matter has a ‘given’ expansion *factor* within itself?"

Crudely, yes.

Oh, shit. No, I realise that chelle is going to get it wrong again.

The expansion is on the space the matter is within.

The expansion is not in the matter itself.

Well, though it was pretty obvious anyway, it now seems like even chelle has admitted that her inability to understand how gravity and expansion can coexist is entirely based upon her lack of knowledge.

I wonder what that does for her aether, which was demanded as being true because of the above perceived contradiction..?

"Your mistake is thinking that the statement “objects move away from us faster, the further away they are” is an ironclad rule that all objects follow, rather than a general trend."

Actually, it's neither.

Deniers of AGW get this wrong all the time.

There is a trend. Individual motions are imposed upon this trend. The resulting summation for any one object is the redshift seen.

By collecting the redshift of many galaxies of approximately appropriate distance, an averaging of their redhift should cancel out any motion imposed upon the motion imposed by expansion.

Just because the train is moving doesn't mean that your movement within that train cannot happen. Or that by walking to the back of the train that you will never get to your destination.

Chelle, "z" is not a unique value. And Z is not the value of expansion of space. I don't know why you think so. Z is a measure of redshift to a given object. For one star or galaxy or supernova or whatever it has a certain value, for another it has a different one.
z=observed wavelenght - emited wavelenght/emited wavelenght

From the formula you can clearly see that this has nothing to do with whole universe. Nor that it's some sort of constant.

p.s. and it needn't be only redshift, it can as well be blueshift, depending if the value is positive or negative.

"I don’t know why you think so. Z is a measure of redshift to a given object."

Because chelle isn't here to learn but to pollute the blog with bollocks.

Sinisa,

"Chelle, “z” is not a unique value. And Z is not the value of expansion of space. I don’t know why you think so. Z is a measure of redshift to a given object. For one star or galaxy or supernova or whatever it has a certain value, for another it has a different one.
z=observed wavelenght – emited wavelenght/emited wavelenght

From the formula you can clearly see that this has nothing to do with whole universe. Nor that it’s some sort of constant."

In the simulations it is a set constant, and this why I also made that comment in the other topic:

"Now if you look at the images at the bottom of those Millenium-II simulations:
http://www.mpa-garching.mpg.de/galform/millennium-II/
Than you end up with all kind of different structures with Red Shift 6, 2, 1, and 0.
Now it’s interesting that Ethan used the image with Red Shift ‘zero’ when he talked about superstructures making up the Universe …"

"In the simulations it is a set constant"

No it isn't.

"and this why I also made that comment in the other topic:"

And that is the reason why you're wrong in that comment in the other topic: it isn't a constant in the simulation.

Did you fail HARD in maths, chelle?

You know, when they ask something like:

If y=x^2 + 3x - 8 what is the value of y when x=2?

Because you'd be all "Oh is x a constant then???"

“In the simulations it is a set constant"

No it's not! From what do you gather that??? You have the same frame rendered with different redshift clearly showing the effects of it. You see the same structure but with redshift of 1, 2, 6 etc.. and you can clearly see how clusters become less and less prominent as the redshift increases. How can you say it's constant when in one image it's z=1 and in other z=6? Do you know what constant means?

"No it’s not! From what do you gather that???"

Pulled from her arse.

Sinisa,

"Z is a measure of redshift to a given object. For one star or galaxy or supernova or whatever it has a certain value, for another it has a different one.

From the formula you can clearly see that this has nothing to do with whole universe. Nor that it’s some sort of constant."

Z is in each frame of the simulation (0,1,2,6) the same for ALL the objects. So it doesn't seems like every object has a different value like you first said, and if so, than there 'is' some sort of constant.

Perhaps better would be saying that all the objects have the same Z-value, so how is the difference in distance for each object (Expansion vs. Gravity) embedded into the program?

"Z is in each frame of the simulation (0,1,2,6) the same for ALL the objects"

Nope, the objects with a different Z are not included.

Idiot.

"Perhaps better would be saying that all the objects have the same Z-value, so how is the difference in distance for each object "

If I select those households that have two children and work out the average income and spread of incomes, would you be going "So everyone has two children???"?

Chelle,

objects don't have z-value per say. Mhm.. how to put this so you understand. Ok, let's forget the millenium simulation for a bit. Let's downscale it just for the sake of argument and simplify it. Now don't stick to the following explanation to strictly cause the values aren't the same, but the concept is.

Let's say i have a light bulb 1 meter from me and i measure the incoming spectrum. I get a certain expected value. Now, let that lightbulb move away from me and I measure the spectrum again, i notice the colors have shifted by a certain amount. That amount is called a redshift (or blueshift if it's moving towards me). That's the "z" value. The faster it moves away, the bigger "z" value will be. Remember, emited wavelenght and observed wavelenght. The lightbulb is the same in both cases. It doesn't have it's intrinsic z-value. I, the observer, measure the value. The object measured doesn't change any of it's properties. It still emits the same light the same way, the speed it moves away from me dictates the "z" value. If it moves i.e 50m/s from me i might get a "z" value of 1.75. If it moves away 250 m/s, I might get a value of z=3.5 and so on.

Now, to the milenium sim. Each rendered frame with different "z" value shows what the observer sees. Observer being the camera or you/me looking at the clusters. The clusters don't change. Our view of them changes.

To busy to catch up with this thread or think this comment through, but my understanding was that the z value is effectively the "time axis" of the simulation, with z proportional to both elapsed time and cosmological expansion rate. I'm prepared to be told I got that completely wrong though!

Sinisa,

Thanks for your explanation, although it is not very different from my example where I used a dimmer to turn down the lights. As you turn down the dimmer over time, Stars seem to be moving further away. In a fixed matrix with each solar object at the same distance and same mass your example will work perfectly.

Now let's look at the Millennium Sim:
http://www.mpa-garching.mpg.de/galform/millennium-II/Images/evol_12pane…

• Here you start with a situation at the bottom, where there Z=0 this means that all is Static, is that correct?
• Next have all the objects 'race' away from each other at a set speed Z=0.99 it is all clear. But now my question is again how is the difference in distance for each object (Expansion vs. Gravity) embedded into the program? Some objects should be hold back more than others due to gravity. And a 'knot' in that structure should slow down the expansion rate 'Z' in that tight place because it is also the case in our Milky Way, Gravity slows down the Expansion, so Z can not be the same everywhere. Here I also like to again add a previous question:

For Expanding Space to pull the matter within it along, that overrules Gravity, that space needs to apply an attraction force on matter to pull it along, otherwise ‘Space’ is just flying by, or does each piece of matter has a ‘given’ expansion *factor* within itself?

If so, than that 'expansion factor' needs to be embedded into every atom that makes up a cluster that includes you and me, but if our Milky Way is holding it together than how can it all be expanding, how does that work?

What you now should do is have a look at the link that I'm posting in my next comment, and see how the Universe and it's Red Shift really looks like, and you'll see that there is a more circular ripple pattern around our position as if someone had drop a pebble in a pond, so it all looks more like a Little Bang / Blast that we created, than stuff expanding in ALL directions all over the Universe.

Here's the image:

http://www.sdss.org/includes/sideimages/sdss_pie2.html

"Thanks for your explanation, although it is not very different from my example where I used a dimmer to turn down the lights."

Nope, its very different. SL's light is moving away, NOT getting dimmer.

"If so, than that ‘expansion factor’ needs to be embedded into every atom"

Nope, it doesn't.

The atom doesn't get an expansion factor. Space expands.

"• Here you start with a situation at the bottom, where there Z=0 this means that all is Static, is that correct?"

No.

"• Next have all the objects ‘race’ away from each other at a set speed Z=0.99"

No, this doesn't happen.

"But now my question is again how is the difference in distance for each object (Expansion vs. Gravity) "

the difference in distance for each object is not expansion vs gravity.

"Some objects should be hold back more than others due to gravity."

No. Expansion is moving space further apart. Objects are moving within that space. There is no "holding back".

"And a ‘knot’ in that structure should slow down the expansion rate ‘Z’ "

It does not.

"Gravity slows down the Expansion"

No it doesn't.

Gravity pulls objects towards a more massive centre. Expansion changes space.

Gravity : Objects
Expansion: Space.

"but if our Milky Way is holding it together than how can it all be expanding, how does that work?"

Because gravity is pulling masses together, expansion is moving things apart.

One does not preclude the other.

"and you’ll see that there is a more circular ripple pattern around our position as if someone had drop a pebble in a pond"

There is no pebble. There is no pond.

Hell, there is no ripple.

@ Chelle

"although it is not very different from my example where I used a dimmer to turn down the lights"

it's very different, since you are changing the intensity of the source. This is not what happens in space. The source needs to stay the same, hence the need for standard candle and type Ia supernova.

"In a fixed matrix with each solar object at the same distance and same mass your example will work"

Like I said, the lightbulb example is simplification, but there is no need for fixed matrix (don't even understand to what matrix you are reffering?)

"Next have all the objects ‘race’ away from each other at a set speed Z=0.99 it is all clear."

No no no! "z" is not a measure of speed! The example with lightbulb shows just what "z" is. But in space the redshift is NOT CAUSED by the speed of galaxies or clusters themselves. It is caused by the metric expansion of space. Or in other words, the redshift is not caused by speed of galaxy but by property of spacetime. This is a huge difference and extremely important one.

"But now my question is again how is the difference in distance for each object embedded into the program?"

I can't answer this question since I didn't program the simulation. But you need to understand that redshift is not a measure of distance. Distance is measured by i.e. measuring the brightness of the source, redshift gives the spectrum of the source.

"Some objects should be hold back more than others due to gravity"
this is true and in no way is it broken in the sim.

"also the case in our Milky Way, Gravity slows down the Expansion"

No again! Gravity doesn't slow the expansion. Expansion is a property of space, gravity causes the objects that it "attracts" (to use newtonian term, altough not really true) to stay relatively together. i.e. the forces holding molecules and atoms of your body together don't cause the gravity to attract you less towards the center of the earth. It's just the case of which one is a stronger force for a given scenario. This is actually elementary school physics... adding vector forces together or subtracting.

", and you’ll see that there is a more circular ripple pattern around our position as if someone had drop a pebble in a pond"

that's the image from sloan digital survey. That has nothing to do with millenium sim. Why are confusing yourself even more? Millenium sim deals with replicating the obervation, and so far it does very successful job. The image you posted from sloan is direct observation of our local cluster. The whole point of millenium sim. was to try to replicate sloan's survey. And it did.

"looks more like a Little Bang / Blast that we created"

Say what? We created? What in the world are you talking about. If someone from i.e. Andromeda galaxy did the survey they would get the same image. Then "they" created it and not us? Don't you see the issue with that line of reasoning.

It seems to me that expansion is what confuses you more than redshift. So let me quote wiki:
"The metric expansion of space is the increase of distance with time between distant parts of the universe. It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. "

Note the last part... NOT BY MOTION OUTWARD into preexisting space. The galaxies are not mowing away somewhere where there is space yet they haven't been there. The space is expanding, in a way, onto itself.

"Why are confusing yourself even more?"

In the hope of hiding the fact that chelle has nothing other than ignorance to complain about.

Sinisa,

"The galaxies are not moving away somewhere where there is space yet they haven’t been there. The space is expanding, in a way, onto itself."

You are saying all the time that I am crazy, but this makes absolutely no sense at all, but ok.

Anyway an other thing is how can you have a shift of a Wave when you have no Medium, it is the speed in relation to the medium that causes stretching or compression, it is so for water or sound-waves traveling through the air; but when you have no medium each particle that is emitted should be exactly the same.

Regarding that other picture, nope if you had it taken from an other galaxy, the blue area would be around that galaxy, and not ours, and the circular ripple pattern also around that pov, and no longer around ours, that what I mean with Little Bang/Blast, we are blowing stuff all around, and that's how you generate such an circular pattern.

"You are saying all the time that I am crazy, but this makes absolutely no sense at all"

Yes, this is how the crazy is diagnosed.

This is why the psychologist says "Admitting the problem is the first step to getting better".

"Anyway an other thing is how can you have a shift of a Wave when you have no Medium"

Do you know ANYTHING about electric fields and magnetic fields and the motor rule?

Here's a potted version:

A changing electric field causes a magnetic field. A changing magnetic field causes an electric field. Therefore the changing electric field of a photon causes the projection of a magnetic field. That causes the projection of an electric field. And that is the photon.

There is no medium.

"it is the speed in relation to the medium that causes stretching or compression"

If that were true, then the michelson-morely experiment would have noticed a change in the speed of light.

They didn't.

Ergo Aether doesn't exist.

"and that’s how you generate such an circular pattern."

There is no circular pattern.

I bet you are a believer in crop circles too, aren't you.

"but when you have no medium each particle that is emitted should be exactly the same."

Why?

“it is the speed in relation to the medium that causes stretching or compression”

If that were true, then the michelson-morely experiment would have noticed a change in the speed of light.

They didn’t.

Ergo Aether doesn’t exist.

No, The Michelson–Morley proves that motion does not influence the the behaviour of light (in the Aether), and so it proves that Red Shift is no valuable proof for Stars that would be moving away. There is only proof that Gravity causes a Red Shift and Einstein spoke about GR as a *new* Aether.

Ergo what this all proves, is that the Stars aren't moving away and are relatively static, and that it is an *effect* caused by the continuous expanding change of the state of the Aether around us, and this picture proves it:

http://www.sdss.org/includes/sideimages/sdss_pie2.html

All the linear red zones point to us.

"Red Shift is no valuable proof for Stars that would be moving away"

they are NOT moving away.. space between us and them is expanding.

" and that it is an *effect* caused by the continuous expanding .... of the Aether"

at least be consistent with yourself... every 2 weeks you have a different theory... 2 weeks ago you werent saying this...

but in the end.. whatever rocks your boat.. believe in aether and torpedoes.. or whatever.. untill you offer evidence and proof it's quack..

"The Michelson–Morley proves that motion does not influence the the behaviour of light (in the Aether),"

So speed isn't a behaviour of light???

Sinisa,

” and that it is an *effect* caused by the continuous expanding …. of the Aether”

Ok, so you cut out 'change of the state'.

I'm not changing anything, and the image gives you all the proof that is needed.

"I’m not changing anything,"

You certainly aren't. You're inconsistent with every statement you make, and this is why you aren't changing anything.

Oh, did you mean "changing anything in my statement"? No, you do that a lot.

What image? What proof?

You have already shown you haven't a freaking clue what the images you post mean.

"There is only proof that Gravity causes a Red Shift "

BOLLOCKS.

You can prove doppler shift with light.

It is inherent to the idea of a wave that this be true.

Gravity, however, leads to the proof that light is a particle, since you have to accelerate THE MEDIUM to get a frequency shift and this would NOT be the same change as you get with real GR shift.

Light that is emitted will always have the same frequency, e.g. a green leaf will always look green, and won't become red, the faster it moves away from us. Sure a pulse will expand or contract like for a radar gun, but not the energy of the photon itself.

I cut "change of state" on purpose to try to make sense of your sentence.. but ok, have it your way... and that way.. it means nothing... It's gramaticaly wrong, it's logicaly wrong.

Change of state can't expand or contract or do anything. How about: change of weather is contracting. That's just retarded, like many things you write here.

“Change of state can’t expand or contract or do anything."

http://en.wikipedia.org/wiki/Thermodynamics

"That’s just retarded, like *nearly everything* you write here."

FTFY.

"Light that is emitted will always have the same frequency"

See, you're changing things AGAIN.

Earlier:

“There is only proof that Gravity causes a Red Shift ”

Now you're saying there cannot ever be a redshift.

Retard.

(oh, and a green leef isn't light emitting)

Thermodynamics????????

My god. The stupidity factor is over 9000.

OK, so where is the solid light? Where is the liquid light and where is the gaseous light:?

FFS, you're a thick cunt.

An go on, explain how that is any answer.

Or was it just buzzword bingo for you?

"Oh, thermodynamics has things changing state. It also has expansion and contraction, so all three words are there, lets get a link to it. It may make someone thing I answered it".

“Oh, thermodynamics has things changing state. It also has expansion and contraction, so all three words are there, lets get a link to it. It may make someone thing I answered it”

my thoughts exactly

Apart from you spelled think correctly...?

"Light that is emitted will always have the same frequency e.g. a green leaf will always look green"

I'm starting to think that you live in some bizzare parallel universe with only connection to our world being this blog here. Shame you have to dump your trash here. Was a great place until you started to spread your bull*** around.
btw, leafs don't emit light. Not on this planet.

Sinisa,

"btw, leafs don’t emit light. Not on this planet."

Yes they do, e.g. the electrons that make up a leaf.

The key components of Feynman's presentation of QED are three basic actions.
• A photon goes from one place and time to another place and time.
• An electron goes from one place and time to another place and time.
• An electron emits or absorbs a photon at a certain place and time.
http://en.wikipedia.org/wiki/Quantum_electrodynamics#Feynman.27s_view_o…

"“btw, leafs don’t emit light. Not on this planet.”
Yes they do"

ahh.. so in the evening the leaves go to sleep and stop emitting light. Interesting...

"green leaf will always look green" ... thanks for the insight that in your parallel dimension there is no autumn. Shame.. it's a nice time of year.. with all the oranges and reds.. rofl.

I know, crank science at its best!

Leaves emitting light!!!!

I really am literally LOLing.

"Sure a pulse will expand or contract like for a radar gun, but not the energy of the photon itself."

Chelle, you really do need to sit down and spend some time contemplating the chasm between what you think you know and what you actually know.

A radar pulse returned from a moving target will indeed be longer or shorter than the transmitted one. Clocking a flat out Bugatti Veyron should change the pulse width by about one part in a couple of million. If you know a way to measure this I would be interested professionally. A Doppler radar measures the frequency change of the returned signal. I can assure you that energy of the returned frequency shifted photon is not the same as that of the transmitted one. The energy is directly proportional to frequency, but don't take my word for it, use this calculator

http://www.1728.org/freqwave.htm

Invalidating these results would not be "a small change" to existing Physics. It would blow the heart out of EM theory, Quantum Mechanics, even the Quantum Electrodynamics you linked to above. You are ether the greatest scientist that has ever lived or wrong. Which do you think it is?

P.S. I have actually designed signal processing electronics for Doppler radars, and this bit of Physics seems to work fine. How do you make a living?

"How do you make a living?"

She lives off the state, I bet.

DavidL,

So you think that a green apple becomes more blue when it is thrown to you, and more red when you throw it away? Now why don't we film it, and compare colors at equal distances, so we are sure that we aren't measuring the intervals in distance which may influence frequency and wavelength, just the color spectrum of the photon that comes of the apple. Now that shouldn't be a hard thing to do, and no it wouldn't change the hearth of science, only just very maybe that of the Big Bang theory.

p.s. I do graphics and computer simulations, but indeed might start to live from the state because economics is slow lately.

"So you think that a green apple becomes more blue when it is thrown to you"

As I said in my above post, I not only think that, but I have earned a considerable amount of money by measuring the "colour" change, albeit at 3 orders of magnitude lower in frequency.

If you knew much about graphics you would realise "filming" it would be of no use as cameras measure only the relative amplitudes of the three primary colours. Observing the effect would require a spectrometer. Not my area of expertise, but I am confident if you put your apple on a rim of a platter, spin it fast enough, illuminate it and give me a spectrometer on an optical path tangential to that rim, I could tell you which way the platter was spinning from the spectrum of the reflected light alone.

"..but indeed might start to live from the state because economics is slow lately."

Good to see reality impinges on your life somewhere.

DavidL,

"Observing the effect would require a spectrometer. Not my area of expertise, but I am confident if you put your apple on a rim of a platter, spin it fast enough, illuminate it and give me a spectrometer on an optical path tangential to that rim, I could tell you which way the platter was spinning from the spectrum of the reflected light alone."

You might be right, but I think your own money making precision measurements are based on interval. Usually ideas like this have already been tested so let's look if we can find a paper on it; if not, let's look for someone who could do this rather simple test, so we know for sure if you're right.

"You might be right"

No, he is right. You're talking to a plumber telling you that PTFE tape is useful as a very thin film to seal metal scew joints and you saying "you might be right" because you're stuck on the idea that PTFE is ONLY a solid lubricant.

"more blue when it is thrown to you, and more red when you throw it away?"

Seems you don't even know what Red Shift is.

But, like everything else you don't understand, this doesn't stop you pretending you have worked out it is wrong.

"p.s. I do graphics and computer simulations"

No you don't. You're lying YET AGAIN.

You might be right, but I think your own money making precision measurements are based on interval.

I'm not sure if that comment is about Doppler radars or spectrometry.

If the former, are you seriously claiming that if I design an electronic circuit to multiply two analog signal together and measure the frequency of the resulting signal , what I get when I build the circuit is something that will magically measure an "interval" instead? Sort of like Marconi switching on his first prototype radio and being amazed at the picture quality. What a strange world you live in.

If the latter then it is not something you are likely to find a paper on. It's not cutting edge Physics, just a common sense demonstration of the same principle as getting caught by a radar speed trap. The only difference is that frequencies in the visible spectrum are way too high to process with current electronic technology so completely different measurement methods are required. And of course there is no "interval" to measure in this case. An apple may appear at regular intervals, but adding more apples or changing the diameter of the platter would yield the same result if that interval varies. The frequency shift will always be related to the SPEED of the apple with respect to the spectrometer

I think I know what chelle means when she claims she works with graphics and computer simulations.

She plays The Sims.

DavidL,

You might be right, but I think your own money making precision measurements are based on interval.

I’m not sure if that comment is about Doppler radars or spectrometry.

What you do with your Radar gun, is similar to trowing every second a ball into one direction, now the speed of an incoming wall/car will defined the amount of balls that get to be bounced back within one time period, and this defines the speed of the car, so it's dependent on the interval of the signal you send.

What I'm saying is that you should trow one ball from that incoming wall/car and be able measure the speed of the car and the Doppler-effect, just like in the case of a moving ambulance, and this is something what you can't do because the speed of light is constant, and the emission of a photon instant (QM). So it would make no difference if the apple was moving away, standing still or moving towards you at the time of emission, so there is no Doppler-effect observable and the Apple will keep its green color, there will be no Shift, and the same goes for Solar bodies that are moving away, you need to send a signal towards them at a set frequency and calculate the rebound, to measure their velocity. That's how things in the real world work.

"What you do with your Radar gun, is similar to trowing every second a ball into one direction"

Nope. What he does with his radar gun is show the change in frequency when the signal reflects off the target.

This is the Doppler Effect.

Have you heard of that? You claimed to have done CFD so you must have.

Have you?

Doppler Effect.

Look it up.

Chelle the world must seem really unfair to you. You must look out with dismay to a world full of Scientists and Engineers who achieve the most wondrous things despite being total idiots who don't have the remotest idea how anything works. And not one of them has ever thought to tap your genius

A few years ago I watched with interest as a whole group of these idiots working for the European Space Agency sent the Cassini spacecraft to Saturn carrying a little probe called Huygens to land on its moon Titan. The little fellow could not talk to earth by itself, so Cassini would relay his messages back to earth. So they gave the little guy the radio equivalent of a blue light to flash at "mum" and gave "mum" a receiver that could only see blue light (keeps the noise out) And do you know what these idiots did? They forgot about the Doppler Effect. Doh! Fortunately, just in time a couple of them realised that when junior set off on his own, accelerating towards his final rendezvous, his blue light would begin to turn a bit purple, and pretty soon mum would not be able to pick up a word of what he was saying. The fight plan was modified mid mission and the idiots succeeded spectacularly.

Check the wiki link below, especially the paragraph "A critical design flaw resolved" and tell me how you would have saved the mission

http://en.wikipedia.org/wiki/Huygens_%28spacecraft%29
"A critical design flaw resolved"

David, don't you realise what chelle has found out? Your work on radars only appears to work because you get paid to make them!

Yup, the same old crap the AGW deniers use is being used by the current idiot troll.

Chelle,

Yes, the apple really is redder (or greener) depending on the relative velocity between you and the apple. That's what the doppler effect is all about. Consider an object that appears to be yellow to a comoving observer. That object might well appear to be red if you and the object are separating fast enough. It may well appear to be green if you and the object are approaching each other rapidly enough.

So what color is the object really? I guess you could say that the object has a "proper color" (analogous to concepts like proper time and proper length in SR) of yellow. However, relativity (you know, proposed by that Einstein guy you're fond of quoting) says that there are no preferred reference frames. Therefore, the object "really" is yellow AND green AND red, depending on the reference frame of the observer. Color is indeed a relative notion, not an absolute one.

I realize that this seems odd, but that's mainly because the speeds involved with making an object change its observed color are higher by far than any speeds ever obtained by human observers.

Wow,

"This is the Doppler Effect."

Yes, that is the Doppler-effect, but first he needs to set up a medium with intervals, between him and the moving object. Just like sound-waves have a medium between the ambulance and the listener. The speed of sound is based on the interval between the molecules that make up the 'air'. No air no sound waves; no generated radar signal no Doppler-effect.

DavidL,

For Huygens it is the same thing, the radio signal is set, of course when you move relatively of that signal in-between its intervals you have a Doppler-effect, just like when you would have wanted to catch those balls that are thrown every second, if you drive too fast you they might come to fast for you to process them.

So again for measuring the speed of those distant galaxies you need to set a signal, and relative to that signal you can measure the speed of the moving object. For the Hubble Red Shift, you only get a change in energy of the incoming photons, and that is not enough. It's like getting back one ball that is colder, when you know that when it left it had a set temperature, the only thing that could have happened is that it got to be cooled down along the way.

Sean T,

That's wrong because let's say that the speed of light is constant in a vacuum, and absorption and emission of a photon by an electron is instant (QM), so there is nothing changing in-between, unless you change the speed of light.

"and absorption and emission of a photon by an electron is instant (QM)"

No, they are not instant.

And what makes you think that it is something to do with QM that it would be?

"but first he needs to set up a medium with intervals, between him and the moving object"

No he doesn't.

"Just like sound-waves have a medium between the ambulance and the listener."

Sound waves are not light waves you ignorant fuckwit.

A changing magnetic field causes a changing electric field which causes a changing magnetic field, and so a photon can propogate ITSELF.

"for measuring the speed of those distant galaxies you need to set a signal"

WHAT????

chelle,

Nothing in the doppler effect has anything to do with changing the speed of light. Simple physics: the speed of light = the frequency x wavelength. When an object is viewed by a moving observer, the frequency depends on the relative motion of the observer and the object. The wavelength also depends on this relative motion. The product of the two is invariant; that's what started Einstein on special relativity to begin with. The speed of light is the same in ALL reference frames.

Now again, more basic physics: a frequency measurement is really nothing more than a time measurement. Frequency is simply an inverse time. A wavelength measurement is of course a distance measurement. Special relativity tells us that the speed of light is constant no matter the relative motion of the source and observer (at least in inertial reference frames). Since frequency is really time and wavelength is distance, the doppler effect for light is nothing more than a manifestation of length contraction and time dilation, as spelled out in any good text on special relativity. I suggest you read about these before rejecting the doppler effect.

Chelle,

Just a quick quiz for you: Let's assume that you and I meet somewhere and set super-accurate timers to zero. After this, we leave our meeting places with two different velocities, Vs and Vc. We start our timers at the same time as we depart. We both then observe a flash of light from an assistant. When we compare our results, I say that the flash of light occured when my timer read ts, you say it occurred when your timer read tc. Question: at what time did the flash of light REALLY occur? Who's time is the right one?

BTW Chelle, one other question in the above: is it necessarily true that ts = tc?

Chelle @11:28:

Yes, that is the Doppler-effect, but first he needs to set up a medium with intervals, between him and the moving object. Just like sound-waves have a medium between the ambulance and the listener. The speed of sound is based on the interval between the molecules that make up the ‘air’. No air no sound waves; no generated radar signal no Doppler-effect.

Chelle, I already explained this to you either way up-thread or in an earlier thread. Photons are not acoustic waves; their wave-like nature is not due compression/energy transfer between adjacent particles. We use the same word "wave" for both but they are different phenomena. They are not just like sound waves. Thinking they are like sound waves shows how little you know about the subject.

Sean T,

You could look at the Doppler-effect that DavidL has for his Radar, and in the case of Huygens, basically as that 'flash of light' that you mention in your little quiz.

When you set a timer for it to *flash* every second, and you have a mirror that moves; than you know when *flashes* comes back at an interval speed of 0.8 sec. and next 0.6 sec., that the mirror is accelerating towards you, because the intervals or frequency becomes smaller, and this is like how you explain, "nothing more than a manifestation of length contraction and time dilation.

But now comes the difficult part of the Doppler-effect and Red Shift of galaxies in Space; and what I would like to hear your opinion on, is how much time it takes for a *flash* of light to emit one photon, that is caused by this QM effect:

In physics, emission is the process by which a higher energy quantum mechanical state of a particle becomes converted to a lower one through the emission of a photon, resulting in the production of light.
http://en.wikipedia.org/wiki/Emission_spectrum

I presume that the emission of a photon is instant, because Electrons jump from one QM state to an other just like that, or am I wrong here?

If I'm wrong, than could you please tell me how long it takes, because than you would indeed have a similar situation as when setting a frequency (time interval), by lighting your *flash* every second. And a photon would become longer when you move away from me, and shorter when you move towards me, but if a photon is 'born' with its wavelength 'set' instantaneously, than it won't change after that. You see when a photon is generated there is no time involved, the length of the wave is embedded within one photon, or not?

The same goes for the absorption process that is instantaneously. So it's not like a Radio signal that you give a pulse (frequency), and yes such a signal can than have a Doppler-effect, but not those who are made by Electrons jumping from one QM state to an other, and if I'm correct, it are exactly those photons that generate the Red Shift.

"When you set a timer for it to *flash* every second, and you have a mirror that moves; than you know when *flashes* comes back at an interval speed of 0.8 sec. and next 0.6 sec., that the mirror is accelerating towards you,"

That isn't the doppler effect.

The doppler effect changes the frequency of the light.

eric,

"Chelle, I already explained this to you either way up-thread or in an earlier thread. Photons are not acoustic waves ..."

Sigh, I was referring here to how the Radar signal set's a field with an interval (frequency) just like how air has an interval based on the distance between the molecules ... If you make a sound than it travels depending on the speed of the spacing between the molecules if you make a sound while moving forward you are adding compression. In the same way if you have a mirror that stands still that bounces back the Radar signal, the bounced back signal could travel supposedly at same frequency (interval) of that send out Radar signal, now if the mirror moves towards you, than things starts to change and you get a Doppler-effect, the send out Radar signal becomes compressed.

"and what I would like to hear your opinion on, is how much time it takes for a *flash* of light to emit one photon"

What is the emission mechanism?

www.pmrinfosolutions.com/process1/.../24...7.../po-7-10-491.doc

150 picoseconds is common. But some take much much longer. The metastable state that is the basis of measuring time takes milliseconds.

"I presume that the emission of a photon is instant, because Electrons jump from one QM state to an other just like that, or am I wrong here"

You are VERY wrong here.

"You see when a photon is generated there is no time involved, the length of the wave is embedded within one photon, or not?"

Not.

"the bounced back signal could travel supposedly at same frequency (interval) of that send out Radar signal"

Only if the object it bounced off were not moving.

Chelle: “and absorption and emission of a photon by an electron is instant (QM)”

Chelle: “I presume that the emission of a photon is instant, because Electrons jump from one QM state to an other just like that, or am I wrong here”

Apparently not having the faintest clue is no impediment to chelle impeding science and claiming it all wrong.

Ethan, may I just say that you're fucking things up royally here letting chelle continue to spout her complete bollocks and ensuring that NOBODY learns ANYTHING.

Well done for fucking up the one thing you say you're trying to do.

Wow, Chelle, and everyone else,

I have been thinking about what's been going on in my comments for about the last week, and how to deal with everything in the most responsible way I can. I will have something to say (and do) about it starting this weekend.

Sit tight for just another day or two; I am aware it is overdue and I hope everyone feels empowered and yet not unfairly censored at the same time.

Come on Wow you are doing a great job there's no need to start pointing your finger to the boss.

btw energy states within an Atom are discrete so it doesn't take any time to jump from one state to an other. Yes, it might take some time before it jumps, but once it jumps, it's already there.

Fair enough, but chelle's been reduced to finally saying "Oh, I assumed this, therefore aether".

Remember that sometimes compromise is not the answer. You don't tell your mugger "Well, lets compromise on you taking HALF my money, OK?"

And expecting compromise leads the sly nutcase to go fanatical. I.e. if your plumber knows you're going to offer half of what they give as a quote, they'll quote four times what they want.

"btw energy states within an Atom are discrete so it doesn’t take any time to jump from one state to an other"

1) that doesn't follow. There's no causal link bettween discrete energy levels and time to emit radiation in electron transitions
2) its not even true. Heisenberg uncertainty principle.
3) You're a frigging nutjob.

“btw energy states within an Atom are discrete so it doesn’t take any time to jump from one state to an other”

1) that doesn’t follow. There’s no causal link bettween discrete energy levels and time to emit radiation in electron transitions

There is simply no time between the discrete levels. It is either State A or State B, there is nothing in between, not even time. Yes it might take a long time before A goes to B, but when it does, it takes no time.

So now tell me how those emitted photons could be stretched over time e.g. in wavelength, when there is no time to be stretched?

"There is simply no time between the discrete levels. "

There's no difference between a duck's legs either. And, similarly, both are nonsensical statements.

" It is either State A or State B, there is nothing in between"

Yes there is.

"when there is no time to be stretched?"

Since there is time to be stretched, your question is nonsensical.

” It is either State A or State B, there is nothing in between”

Yes there is.

No, if there was, there would be something between A and B and there isn't anything in between. Sure when you have two electrons you can get an 'AB', but the basic photon that jumps from A to B is discrete and can't be stretched it is a closed quanta. So yes in a two electron set up you can stretch time as long as you like, and generate some shift, but the individual quanta generated by one jumping electron can't be stretched by motion of the Atom, also because of the discrete limitations of possible states within the Atom. If what you say is right, than Atoms could stretch out into space, Wow!

"No, if there was, there would be something between A and B "

There is.

"but the basic photon that jumps from A to B is discrete and can’t be stretched"

Yes it can.

" it is a closed quanta."

That is completely made up bullshit.

"If what you say is right, than Atoms could stretch out into space"

They do.

Did you think they were point objects???

arxiv.org/pdf/0803.2596

“but the basic photon that jumps from A to B is discrete and can’t be stretched”

Yes it can.

If it could be stretched than you would measure values in-between A and B and there are none, the Energy-levels are discrete. Let's say that a photon is stretched, than you still aren't measuring any difference because you only have discrete measurement results, that's how you know.

“If what you say is right, than Atoms could stretch out into space”

They do.

What you are saying with your Expansion theory is that Atoms are bound together within the Milky Way by gravity and all the other forces, but once outside the Milky Way everything can stretch. But even more unique, is that according to you it is still possible that those generated photons can be stretched over time within those Atoms who aren't stretched by Expanding space. Mh, that's a strange situation. So please tell me what is Expansion actually doing within those atoms, when photons generated by electrons jumping from state A to state B are created. btw in those stretched photons there is nothing keeping them together; one part just moves further away from the other when they fly towards us, and not one part is flying faster than the other so what time do these photons have within them, I guess none, so what is there to being stretched?

Where on earth are you getting taught all this crap?

Chelle. I think am beginning to understand at least one of your comprehension problems, so I will have one last go to try to establish if you come here out of a genuine desire to improve your understanding of physics, or you just regard this blog as a platform to tell everybody else how utterly wrong they are about everything. You seem to be either conflating or totally misunderstanding two characteristics of EM radiation: the (temporal) length of a "flash" and the frequency of the EM radiation in it (and a "flash" is almost always many many photons)

The first radars, and many today, operate by transmitting a pulse of energy and measuring the interval to the return. The pulse is as narrow as possible, both to save power and allow more accurate measurement of the echo. This allows you to measure range if you know the speed of light. If you repeat this process you can derive the speed of the target from the rate of change of distance, exactly as you tried to explain the process in one of your earlier posts. The rate you repeat the process at is known as the pulse repetition frequency (prf), but the energy is transmitted at the carrier frequency (CF) In audio terms, this is similar to saying the equipment plays Middle C for a second and repeats this every 20 seconds. But within the one-second note, the sound pressure wave is reversing 524 times. Are you clear on that concept, because from your previous posts you should disagree with none of this?

Now it is possible to build a radar trap based on this, (and laser speed traps operate this way for reasons not relevant here) But by definition Doppler radars designed to record speed operate differently. Instead of timing the arrival of the return pulse, the equipment measures how its frequency has changed from that transmitted. In audio terms you play a one second note of 262 cycles of Middle C and get back 262 cycles of c# in 944mS. You might want to argue that the receiver is still measuring the intervals between each of the 524 individual individual peaks. Strictly speaking this could possibly be true, but it is not the interval you originally meant, and it is simpler to process the signals in the frequency domain rather than have to make precision timings.

And by definition a photon can not pass a point in space in an instant. The property that distinguishes a red photon from a blue one is the number of times per second the EM field associated with it oscillates as it passes (Its frequency). As this is trillions for a visible photon it does not have to take long in human terms to pass and still show its true colour, but it certainly cannot be an instant.

DavidL,

Yes, thanks that is a good summarization, and interesting stuff.

I have to admit that I didn't thought that it could be so refined, as a 'color' photon itself is a composit of tones, that can be more or less compressed. This is leaving me with my last jibber jabber, regarding the 'single' photon that you get from a Hydrogen Atom, that is generated by a single jump from a single electron and that should also be redshifted by the suposed Expansion of Space, how can you stretch such a thing out, and measure it?

"Where on earth are you getting taught all this crap?

So you wonder who else thinks that a basic photon can't be stretched out by Expanding Space? I suppose most people on this planet with a clear head.

No, I wonder where the hell you're getting your crap from, or is it just home-grown?

"I wonder where the hell you’re getting your crap from"

I would say that one of them is Democritus, who posed hypotheses like:

"The theory of Democritus and Leucippus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms lies empty space; that atoms are indestructible; have always been, and always will be, in motion ..."
http://en.wikipedia.org/wiki/Democritus#Atomic_hypothesis

One can ask themselves; what is one light photon an how can it be stretched out by Expanding Space, where does Space get the force to do so and how has it got grip on those photons?

When I have two boats moving from one side to the other, and I want to increase the Space between them, than the Space has to pull those two boats apart from each other, the space has to have grip on them, and apply a force to make those two boats lose energy, it either pushes them apart or pulls them apart, there is NO other way to move them apart, something has to act upon them.

In the same way when an Atom emits a Photon it loses energy as the Electron in the Atom moves to a lower Energy State. So where does the Expanding space get's the energy to push/pull those Photons apart, and make them lose energy; and where is the energy going considering that there are an (almost?) infinite amount of photons traveling through the Universe that are supposedly losing energy at this very moment.

As always the Devil is in the details, and Occam's razor-wise you end up with a building block of a theory, namely the expansion of a single photon, that is extremely dodgy.

"I would say that one of them is Democritus"

OK, so you were taught by democritus....

Get the wrap-around jacket, lads.

"One can ask themselves; what is one light photon an how can it be stretched out by Expanding Space"

Yes, you can.

But if you ask other people, when they answer, you don't get to say "Nuh uh!".

Dear Wow,

Please answer the question, how can a photon be stretched out by Expanding Space?

For change the tone of a note, you physically need to change something ... even in the case of the Magic Flute you need to have a longer or a shorter tube. What is it you say that is physically pulling on the photon, how is it that Space has grip on all those photons who are moving around in ALL directions?

... and why is that all the areas of Red Shifted stars point straight in our direction:
http://www.sdss.org/includes/sideimages/sdss_pie2.html

No.

To be clear, that was the answer to your request "Please answer the question".

The answer is No.

The reason being that these queries have ALL been answered before and you have merely gone "It can't because $SOME_MADE_UP_HOMESTYLE_BOLLOCKS".

So no. It's a waste of everyone's time.

Ok, you don't want to answer perhaps someone else would like to answer the question, how can a photon be stretched out by Expanding Space?

For changing the tone of a note, you physically need to change something … even in the case of the Magic Flute you need to have a longer or a shorter tube. What is it you say that is physically pulling on the photon, how is it that Space has grip on all those photons who are moving around in all directions?

… and why is that all the areas of Red Shifted stars point straight in our direction:
http://www.sdss.org/includes/sideimages/sdss_pie2.html

You're free to wonder.

This engenders nobody to give a shit.

… and why is that all the areas of Red Shifted stars point straight in our direction:

Chelle, once again you seem proud to announce to us all that you understand nothing of what you read. The image you linked to is a false colour image. A sort of graph where colour is used to indicate the age of the galaxies. ALL the galaxies on this plot are red shifted, (the further from the centre the more red shifted). What other explanation can there be other than that they are moving away from us?

Chelle's just doing for the christian fundies what McIntyre et al are doing for the fossil fuel indistries.

Selling doubt.

DavidL,

"ALL the galaxies on this plot are red shifted, (the further from the centre the more red shifted). What other explanation can there be other than that they are moving away from us?

This is what the picture shows:

"Galaxies are colored according to the ages of their stars, with the redder, more strongly clustered points showing galaxies that are made of older stars. The outer circle is at a distance of two billion light years."
http://www.sdss.org/includes/sideimages/sdss_pie2.html

Now look at the distribution of the Oldest Stars in Red, they form a very clear pattern of red 'stripes' that points towards us; or away from us, as if there was a splash.

"This is what the picture shows:"

So the colour is NOT their redshift. Just the age of the galaxy.

And there is no red stripe as is obvious when you take away the white circle inscribed at the two billion light year distance.

Oh, look. If you draw a circle around something, you get a circle...

How amazing.

Anyone who thinks there is one, try this:

Crop the image so you don't see the circle.

The upper half has a sort-of circle very small and off to the left, but if it does exist, it has a "centre" well off the location of us. The upper half as nowhere anything at all resembling a circle.

But then again, you can look at a tree and see a frowning face:

http://cheezburger.com/3204290560

Chelle would have you believe this picture proves the existence of Ents...

“This is what the picture shows:”

So the colour is NOT their redshift. Just the age of the galaxy.

ok, I have corrected my comment to be more precise:

DavidL,

"ALL the galaxies on this plot are red shifted, (the further from the centre the more red shifted). What other explanation can there be other than that they are moving away from us?

This is what the picture ALSO shows:

"Galaxies are colored according to the ages of their stars, with the redder, more strongly clustered points showing galaxies that are made of older stars. The outer circle is at a distance of two billion light years."
http://www.sdss.org/includes/sideimages/sdss_pie2.html

Now look at the distribution of the Oldest Stars in Red, they form a very clear pattern of red 'stripes' that points towards us; or away from us, as if there was a splash.

"they form a very clear pattern of red ‘stripes’ that points towards us ...as if there was a splash. "

No, just the splash of another turd idea from your fevered ego, chelle, into the sewer of crap ideas you love to splash around in.

Earlier you claimed circles. Now they're radials.

Neither exist.

Science is a method to stop us using what we want to see from becoming what we think is there.

And mathematics, being created as a method of measuring the reality rather than the perception would give ZERO credence to the idea of radials pointing to us.

A little edge detection to locate edges (a common trick used by the human visual cortex that enables us to see a complete picture despite our dual blind spot in the eye) and a collection of their length (to denote how much of a line there is) and the vectors (to find out where they point) indicate no significant linear component and absolutely no correlation with a radial toward the origin (to far far below 5% confidence).

You would have a picture showing a face on a tree to be proof of ents.

Oh, and there are no stars indicated on that graph. They would not show up at all at that scale and are indetectable as individual objects.

Again, you merely prove Davids point: you are PROUD of not knowing what the hell you are looking at.

“they form a very clear pattern of red ‘stripes’ that points towards us …as if there was a splash. ”

No, just the splash of another turd idea from your fevered ego, chelle, into the sewer of crap ideas you love to splash around in.

Yes they do. I've added lines so you can see clearly how it matches exactly:

http://tinyurl.com/Alignment-sdss

In the third image I've displaced the radial array and nothing aligns any longer. I could keep on moving it around, but I can not get it aligned anywhere else because there is simply only one fit.

Yes, if you draw lines radially, you will see radial lines.

How much of each line is taken up by a spot of a galaxy?

Almost none of it.

And on the first four lines from 16h clockwise, the "lines" closest to it made by those galaxies DO NOT point along the vector of the line you put on there.

All you've done is put lines on a picture that hasn't got lines on it, then said "look! there are lines here!".

There are techniques of digital image processing that will eliminate your desired bias and TELL you how many lines there are, how long, and where they point.

And what happened to those circles like a ripple in a pond you were blathering on about earlier?

Did you shift the goalposts? Again?

Chelle, from Ethan's last post is is clear we have to stick to science or be banished to his dungeon. I will, and hope you can too. You ask:

" look at the distribution of the Oldest Stars in Red, they form a very clear pattern of red ‘stripes’ that points towards us; or away from us, as if there was a splash."

Firstly, it is undeniable that the image you posted shows EVERY galaxy we see is red-shifted. What other explanation for this is there other than they are moving away from us.? Tell us please in a way which won't get you bumped of the thread. And unless you have a basic understanding of what the image means in its entirety, you can not possibly speculate about the cause of minor details.

Secondly, I don't know for sure what causes the stripes, but I can offer a couple of suggestions.
1) They are an artifact of the resolution of the image and the jpeg compression applied to it in areas where there are more galaxies than pixels Only looking at the original data could remove this possibility

2) Along any direction in space where there is a concentration of galaxies we would expect to see a stripe pointing towards us if the concentration is both moving away from us and spreading out. Older galaxies, coloured in red, will have been spreading out for longer, so will show as the longest stripes.

DavidL,

"Chelle, from Ethan’s last post is is clear we have to stick to science or be banished to his dungeon. I will, and hope you can too."

Can't do, 'cause what I call science isn't yet re-approved as science, so it's slowly time to pack my stuff and move on.

"Firstly, it is undeniable that the image you posted shows EVERY galaxy we see is red-shifted. What other explanation for this is there other than they are moving away from us.?"

I'm not objecting that they are further away, I'm only contesting that they are moving away. I mentioned in my reply's to you already a few times something like a ‘Little Bang’, I'm not going to repeat it here again, just do a quick search.

"Secondly, I don’t know for sure what causes the stripes, but I can offer a couple of suggestions."

I have just asked the question regarding these stripes to an experts from the SSDS-project, and I have taken the freedom to call you 'a friend' and included your suggestion. And I got a lightening fast a reply from Professor Weinberg, and it's a rather cool explanation. So I'm posting it here along my own mail. btw bat's (flitter-mice you find in dungeons), increase there intelligence by sharing information … Here's the Q&A:

Q: I've noticed in the the image of a "Slices through the SDSS 3-dimensional map of the distribution of galaxies.", that the older stars in red, all have some sort of linear pattern that points towards the middle. I have highlighted this 'circular array' in the attached image. It looks a bit like they are splashed out from the center. (http://tinyurl.com/Alignment-sdss)

So my question is, why is there such a pattern, and has it perhaps got something to do with visible limitations from our point of view, or are it dotted trajectories of the same Stars?

A friend of mine suggested this as a reason:

"Along any direction in space where there is a concentration of galaxies we would expect to see a stripe pointing towards us if the concentration is both moving away from us and spreading out. Older galaxies, colored in red, will have been spreading out for longer, so will show as the longest stripes."

I've learned that the 'Expansion of Space' isn't like a real explosion and that Space more or less expands upon itself, therefor the confusion regarding this image, and me taking this opportunity to ask you as an expert.

Q: The red/orange points represent galaxies that are made primarily of old stars, and the green/blue points represent galaxies that are still actively forming young stars. "Passive" (red) galaxies are found preferentially in dense environments; astronomers are still trying to determine why this is so, but it probably occurs in part because these are regions where galaxy formation can start earlier and in part because hot gas between the galaxies can suppress star formation within them.

When the SDSS makes a 3-dimensional map, it takes advantage of Hubble's law, which says that a galaxies velocity is proportional to its distance: v = H_0 * d, where H_0 is Hubble's constant. Hubble's
law is a consequence of the expansion of space, as you say in your message. We measure v, and infer d. However, Hubble's law is not perfect, because in addition to velocities from the expansion of space, galaxies have "peculiar" velocities induced by gravitational accelerations in their immediate surroundings. These peculiar velocities cause an error in the inferred distance, making a galaxy appear closer or further than it really is.

Because red galaxies live in dense environments with strong gravity, they tend to have larger peculiar velocities. Clumps of red galaxies therefore get stretched along the line of sight because of distance errors; these "stripes" pointing towards us are sometimes referred to whimsically as "fingers of god." So your friend's explanation is quite close to the mark --- the difference is that what sets the red galaxies apart is their higher peculiar velocities rather than the longer time they have had to move.

Oops, the second Q should be an A.

Well Chelle it is certainly cool that the good professor is prepared to give up his time to explain his work to you, and if you really have learned that the universe "expands upon itself" then we have made some progress, but I somehow doubt it because he is saying exactly what you have been told here for weeks. As he says, he is measuring red shift and inferring distance. I have no explanation for red shift other than that everything is moving away from us. Nor it seems do you, but you insist it is not moving away even though the professor's data tells you it is. By far the best explanation for everything moving away is that space is expanding, a concept which you led the good professor to believe you already understood.

And bear in mind it is a necessary consequence of his explanation that those whimsical “fingers of god.” would seem to point towards any observer anywhere in the Universe. It does not mean we are special should you think this is the real reason his explanation is cool. Alien Theologists in another galaxy will not be debating why their "fingers of god" are pointing to an outer spiral arm of the Milky Way.

"that the older stars in red, all have some sort of linear pattern that points towards the middle."

A statement OBVIOUSLY untrue.

Chelle, you've been unmoving on your assertions that science is wrong.

scienceblogs.com/startswithabang/2012/09/23/weekend-diversion-you-are-responsible-for-what-you-say/

Get thee hence.

Chelle,
I agree with Wow.

You have already been to Ethan's page:
http://scienceblogs.com/startswithabang/2012/09/23/weekend-diversion-yo…

Go there again. Reread it. Carry-on your endlessly disruptive private science speculations there and no where else on Starts With A Bang blog..

Respect yourself by respecting Ethan and the other commenters here.

Chelle,

You have been warned by multiple people. There is a page where you can continue this discussion and it is not this one.

If you would like to read up on redshift space distortions and "fingers of God" in cosmology, they are well-known effects and google (and even wikipedia) will help you immensely, but this is not the place for that discussion: this page is.

Ethan,

There is no need to continue the discussion, all has been said. But if I may than I would like to add just one more comment to David:

Of course those fingers would always point towards the Galaxy where the observer is located, that's the whole idea.

Sorry for all the trouble, take care.

So leave, then.

Come back when you've had your paper on the whirlpool universe (with added aether) accepted.

We could do with a laugh.

Wow:

Ethan, may I just say that you’re fucking things up royally here letting chelle continue to spout her complete bollocks and ensuring that NOBODY learns ANYTHING.

Personally, I learn interesting and useful information from many of the responses to Chelle. So I don't mind his/her posts, despite the misunderstandings, because he/she tends to act (inadvertently) as a foil or 'straight-man' for other commenters.
I actually mind yours more. Because while you may have useful insights, your machine-gun style of posting makes it extremely difficult to find any of the responses that might interest me. Instead, I end up scroll-wheeling over whole swaths of the conversation, and inevitably I miss something interesting.

Chelle:

how can a photon be stretched out by Expanding Space?

As I understand it, photon magnetic and electic fields oscillate at a given frequency. If the space a photon traverses stretches 'beneath' it as it travels, then the photon will have oscillated fewer times in that space interval than it would have in a non-expanding space. In a sense, the photon traveled further during one oscillation than expected. Fewer oscillations per meter traveled = lower frequency = red shift.

However, I could be wrong about that, so if there are any physicists around who want to correct me, be my guest.

"your machine-gun style of posting"

Stoped Chelle from posting a gish gallop of points in a single post.

Also markedly reduced the segued three-string analogies.

So, although you're entitled to your opinion, arseholes to it is mine.

Scientific Commuting: When Does It Make Sense to Take Alternate Routes?

drorzel — Fri, 12 Aug 2011 08:51:22 +0000

Scientific Commuting: When Does It Make Sense to Take Alternate Routes?

I am an inveterate driver of "back ways" to places. My preferred route to campus involves driving through a whole bunch of residential streets, rather than taking the "main" road leading from our neighborhood to campus. I do this because there are four traffic lights on the main-road route, and they're not well timed, so it's a rare day when I don't get stuck at one or more of them. My preferred route has a lot of stop signs, but very little traffic, so they're quick stops, and I spend more time in motion, which makes me feel like I'm getting there faster.

That's the psychological reason, but does this make physical sense? That is, under what conditions is it actually faster to take the back route, rather than just going down the main road?

Some parameters: the main road route covers 1.7 miles and contains four traffic lights. The back way covers 2.2 miles and has nine stop signs. The speed limit on all of these streets is 30mph, but I usually drive more like 35mph, or 16 m/s to put it in round numbers. I don't really gun my car after any of the stops, so the acceleration is around 2 m/s/s (I'm enough of a dork to have checked this with the accelerometer in my phone, as well as counting "one thousand one, one thousand two..." while accelerating up to speed).

Given that information, how can I estimate the conditions under which it makes practical sense, rather than just psychological sense, to take the longer route rather than the main roads?

I'm a physicist, not an engineer, so I'm going to abstract away a lot of the difficult stuff about this problem. Let's imagine that both the traffic lights and the stop signs are evenly spaced (they aren't) along the route. This divides the 1.7 mile main-road route into five segments (each with a length of 547 m), and the 2.2 mile back way into ten segments (each with a length of 354 m). For each segment, I have to accelerate up to speed at the start, cruise at constant speed for some distance, then decelerate to a stop. In reality, the deceleration tends to be a little faster than the acceleration, but for simplicity, we'll say they're both the same.

So, a little math. We know from introductory kinematics that the time required to accelerate up to some speed v_f at some acceleration a is:

And the distance x covered during that time is:

To find the time required to cover one of the segments, then, we need to include both the time required to speed up at the start and slow down at the end, and also the time to cover the remaining distance. That distance is the length of the segment minus the distance covered while speeding up and slowing down, so using the two equations above, we have:

That looks a little scary, but if you look carefully at that second term, the bit that's subtracted in the numerator simplifies to half of the first term in the equation. which means that the time to complete one segment is just:

Does this look right? Well, looking at the equation, we see that if we increase the acceleration, we decrease the total time. That makes sense, because we spend less time speeding up, and more time cruising at maximum speed. Increasing the final velocity is a little more ambiguous-- it decreases the second term, because the cruising speed is higher, but increases the first, because it takes more time to speed up. Whether this leads to a net increase or a net decrease will depend on the exact values of a, x_seg, and v_f.

The total time required is just the time per segment multiplied by the number of segments, N. This gives us a simple expression for the total time:

(where I've used the fact that N times the segment length is the total length).

So, this gives a simple formula for the time spent to cover each route, which depends on the cruising speed, the acceleration of the car, and the total distance to be covered. this is a dramatic simplification, of course, but it gives you a good idea of the important factors.

So, putting in the numbers from up above, we get a travel time of 210 seconds for the shorter, main-road route, and 300 seconds for the longer back way. Which makes the main-road route clearly better, right?

There's one factor missing, though: the above model assumes that I stop at every light, but does not include time spent waiting for the light to change, which can even things out. The formula is the time spent driving, but if I end up sitting and waiting for more than about a minute and a half, then the two routes are equal in time.

Of course, there's also a best-case scenario for the main-road route, namely hitting all of the lights perfectly so I don't need to stop at all (this essentially never happens, but it's conceivable that it might). The time in that case would just be the time for a single 1.7 mile segment, or about 179 seconds.

So, to sum up: the back way is almost certainly slower, unless I end up sitting at the lights for more than a minute and a half, which isn't that unusual. The main-road route is almost certainly faster, but more variable in time, as there's an unknown waiting time to factor in.

Ultimately, as I said, my reasons for going the back way are psychological, not practical-- sitting at traffic lights pisses me off in a way that having to stop at stop signs does not. So, taking the back way gets me to campus in a better mood than taking the main roads, and that's what really matters, particularly for students in my morning classes.

This calculation does prove once again, though, that if you have a little knowledge of basic physics, there's nothing you can't ~~overthink to a preposterous degree~~ model mathematically.

drorzel Fri, 08/12/2011 - 04:51

Tags

Should be easy enough to get experimental data. Total travel time for each route and number of red lights.

Length of stop lights also varies with locale. In Iowa, 90 seconds average over 4 lights seems like a reasonable time to me. But when I was down in Orlando I was mortified at how long the red stop lights were: some were easily five minutes in the Disney tourist-trap area (but reasonable times in downtown Orlando).

What about fuel consumption?

You can make the psychological reasons fit into a mathematical model if you include variables besides time into your utility/cost model.

Since you prefer the back roads route, you could even derive a bound on your preference for the tradeoff between time and variability.

I agree that moving feels better than waiting, even if the elapsed time is greater. But, as I am now living in the DC area, the basic premise of getting frustrated with a 2-mile commute in Niskenectady seems â¦ flawed.

Anyway, carpool. Commute with the Hamiltonian and you will conserve energy.

I would posit that sitting at traffic lights pisses you off and stop signs don't because with stop signs you're an active participant. The lights force you to be passive.

"Increasing the final velocity is a little more ambiguous... Whether this leads to a net increase or a net decrease will depend on the exact values of a, xseg, and vf"

If you work it out, increasing vf will decrease the time taken up to where the max speed is reached halfway along the segment (obviously, you can't get any faster than that without increasing the acceleration). Logically, increasing the max speed couldn't increase the time taken but it's interesting (at least to me) how that comes out in the maths.

Now you need to model how much more gas you use, and the wear and tear on your brakes. :) Sitting at traffic lights is a bit of a peeve of mine too, and I manage to find the best shortcuts (eventually) in any city we live in--we lived in Vancouver for two years. My wife used to be irritated at me trying all these alternate routes, but when she realized just how quickly we were able to get around (eventually), she started doing the same thing (exploring new routes, looking for the fastest route). Of course, now we live in a city small enough that pretty much any route is the best route so that takes the fun out of things.

Incidentally, if you're so close to campus, why are you driving? That's 20-25 minute walk, and sounds like a nice walk through the suburbs too. I know the U.S. isn't big on making things pedestrian-friendly so maybe you're in one of those areas.

I don't know how many times I've stopped for the night at some hotel only to find I can't actually walk anywhere to stretch my legs--my favourite time was when I asked hotel staff where a good place to walk was. The conversation went like this:

"Walk? You want to walk?"

"Yes, I've been driving all day and I need to stretch my legs"

"Walk?" (calls a coworker over)"He wants to walk." (both now staring at me like I've asked for puppy-flavoured ice-cream).

"Yes, walk"

"You want to walk?"

"Yes, walk. (my two fingers pantomime walking for them). "I saw a mall on my way in. How do I get there?"

"Drive back out the way you came, turn left..."

"No, I want to walk to the mall, not drive to the mall and walk around the mall".

(More staring. Now they suspect I'm a terrorist trying to meet a contact)

"I don't know if you can walk there from here, but you can walk around our parking lot. People take their dogs for walks in the parking lot". Pauses, leans forward confidingly, lowers voice, "We have security cameras on all areas of our parking lots". (Both nodding their heads now, second clerk glancing admiringly at first clerk for his 'subtle' way of letting me know they'll be watching me).

I went walking off-property anyway, and know what, they were right. You can't walk to the mall (big fenced highway in the way). There were also no sidewalks, just roads, and even when I was stumbling along lumpy grassy margins well off the road, I still had cars honking at me. "Look, he's walking, how unnatural...he's probably a terrorist trying to meet a contact".

The best route is the one that causes the least stress. I don't need them there fancy maths to figger that one out.

I've got to go with Andrew here.

1.7 miles vs. 2.2
4 potential stops vs. 9 guaranteed stops

You're probably cutting your gas mileage by 25% going the longer route.

No doubt you're better off than people who spend 90 minutes on the local interstate parking lot, but still...

1.7 or 2.2 miles and you _drive_? And you take the route with more stops/starts? May I suggest you ride your bike or even walk? You'll arrive feeling better, lose weight (if desired), and be healthier.

I used to bike moderately regularly, but that turned out to be one of the primary causes of the crippling muscle spasms in my neck that made it impossible to turn my head. Once I stopped biking (at the suggestion of my physical therapist), I stopped having quite so much pain.

At the moment, walking is out because I have plantar fasciitis in my foot, and after a lot of walking, it feels like I have a hot knife in my shoe. Also, now that SteelyKid is both verbal and mobile, it's more or less impossible to get any work done after I pick her up at 5:30, and driving rather than walking gets me an additional half-hour or so in my working day, which makes a difference.

I thought you were an experimentalist.

If you miss bicycling, but want something more comfortable, you could get a recumbent bike. I've been riding one for over 10 years now, and it really helps. The seat is comfortable; you are sitting upright and so there is no need to contort your neck around; and there is no load on your wrists. Mine is one of the "compact long-wheelbase" types, which are designed for commuting (not racing). Unfortunately, I can't recommend the exact model as the one I ride (a BikeE), because the company went out of business just a couple of years after I bought it. But, Sun makes the EZ-1 bikes, which look to be pretty comparable and reasonably priced.

I share Chad's distaste for having to wait at red lights. I don't know about the area where Chad lives, but in most areas of this state traffic lights are timed to turn the light on the main road red when there is a gap in traffic. That's a perfectly reasonable thing to do when the nearest traffic light is several miles (or more) away. But when you have a bunch of lights closely spaced together, welcome to Plaza Purgatory (commercial strips are where you are most likely to find this scenario): the perverse effect is that having to stop at one light *increases* the probability that you will have to stop at the next light. If it were my goal to encourage speeding and tailgating, I could not design a better system.

In my grad school days, when I often had to make long drives for work-related reasons, I would look for alternative routes just so I could see a different road. Some of these side roads worked out fine: not having to deal with trucks is a significant advantage for the Merritt Parkway over I-95 in SW Connecticut if you are just passing through the state. Others were less effective: Route 206 through Princeton, NJ (this section of I-95 never got built, thus the traffic load on the NJ Turnpike), is a pretty drive in the daytime, but accidents seemed unusually common--I saw three accidents in three one-way trips on that route. As with Chad's back road commuting, it was for psychological reasons.

Nitpick: Unless there are traffic lights at the points Chad turns on and off the main road which are included in the total, the main road route will include at least one stop sign in addition to the traffic lights, and even if the turns account for two of the four traffic lights, Chad has to slow down there anyway (I am assuming that Chad doesn't take corners at 35 mph). So the advantage of the main road route will be less than Chad's inverted envelope suggests.

Aside: Since full throttle acceleration in a modest sports car is only 3.5 m/s/s, 2 m/s/s is not as light footed as you think but might be all that is practical.

You left out one important option: Make a sound physical argument to the local traffic engineers and get them to change the timing of the lights. Unless you are one of only a few people swimming against a spawning run to work, this could be a viable alternative.

I recommend an uncontrolled experiment. Record your time-to-work using one route for a week, then swap routes for a week, rinse and repeat, while graphing the data. If you have a reliable trip mpg calculated off the fuel injectors, record that also. Might be interesting purely for statistical reasons: how regular are the traffic delays and what is the mpg impact of stops -vs- idling?

Then rent a hybrid and see how this changes the answers.

2 miles and you DRIVE?

No wonder we're all doomed.

My brother (applied mathematician) studied his drive to work, too: http://lanseybrothers.blogspot.com/2011/04/how-long-it-takes-to-get-to-work.html

Your calculations are only useful if time is the only factor in the decision. But as you note and just about everyone else chimes in with, there are other factors.

Dave X is right-- this really needs to be modeled as a utility problem.

Oh, this absolutely ought to be modeled as something more complicated than a simple time calculation. I did it this way because I got the idea when I was thinking about things I could do with my intro mechanics class, and this seemed like an angle that could make for an interesting discussion/ calculation.

Another big reason for taking back routes is to minimize the variance of travel time. Main routes are more likely to have unpredictable travel times due to poorly timed lights, accidents, and heavy traffic inducing jams. I'd often take a slower route with a predictable travel time rather than use a highway which was usually faster, but often enough much slower.

Of course, you are based in a part of the country which actually has alternate routes. An awful lot of new developments consist of complex side road system with a single linkage to a main road which is necessary to get anywhere. Growing up on an urban street grid, this suburban tree structure used to drive me nuts. Rather than growing the transportation system for everyone's benefit, developers and their customers would rather rely completely on a limited resource to their own detriment.

As someone using the road less traveled, you are increasing the speed of everyone on the main route. Altruism!
But also, consider changing the handlebars on your bike, so you can sit up more comfortably.

That distance is so short that it really should be walked. It's kind of ironic that one remedy for plantar fasciitis is weigh loss, and walking is a good way to loose weight.

I've walked to work even 7 km, which meant two hours per day, and showering at both ends. The route was along light traffic paths at seashore, and I often stopped at the local beach for an ice cream.

Years ago when I visited Longmont (a one street satellite of Boulder, CO) I was surprised how difficult walking around was. The streets must have been designed by the car industry to discourage walking. Every mall and ice cream kiosk had its own parking lot. More asphalt was used to cover parking lots than streets. It must be a major factor in urban sprawl. Public transport? In USA? Eventually I had to rent a car.

If fuel consumption is an issue, a moped makes sense. Fitting a seat for the SteelyKid isn't difficult. These days there are also electric bikes that can cover that distance, even without daily charging.

It kind of amazes me how people refuse to read the comments in their eternal quest to give unsolicited advice.

Seriously, people.

Thanks for reminding me why I hate applied mathematics ;).
And how lucky I am to be able to choose whether I drive to work or take the bus (takes about the same time, car's basically a backup in case I miss the bus on mornings when I teach early).

There is nothing wrong with taking the route you prefer.

Chad -- a more pertinent question is: why are you driving to work when it's only 2.2 miles max? Try cycling! It costs nothing in fuel and keeps you fit.

Watermelon Collisions - ouch

rallain — Thu, 09 Sep 2010 13:37:39 +0000

Watermelon Collisions - ouch

Through random surfing, I found this clip from The Amazing Race (which is apparently some type of reality show). Don't really know the set up except that it appears some girl is trying to launch watermelons with a slingshot. This looks bad, but she seems to not be seriously injured.

Watermelon smashed on face. Wow. What can I we calculate here? Bring in the video analysis.

How fast was the watermelon going?

First, this is not a very good quality video. The frame rate sucks and there is a very slight panning and zooming (which I will ignore) Second, I really don't have anything to scale the video so I just assumed the girl-launcher was about 1.5 meters tall. Just a guess. Using Tracker Video analysis, I get the following data (where the x-direction is along the direction of motion of the melon):

This shows the motion of the melon both while being launched and when coming back. The first thing I did was to fit a parabola to the very beginning motion. This will give me the initial acceleration with a value of about 120 m/s². Zowza.

I can also get an estimate for the initial and final velocity by fitting a linear function to the data. Note - the melon is actually accelerating (due to the gravitational force) but it is moving so fast, I can ignore this. Doing so, I get a launch speed of about 15 m/s and a returning speed of also about 15 m/s (this is good). First, if the melon gets stuck in the launcher then it should have the same return speed that it had launching (energy conservation). Also, 15 m/s seems like a reasonable speed (around 33 mph).

What about the impact?

This is a little bit more complicated. First, there is the initial impact and then there is the recoil of the head. Here is a plot of the head as a function of time (mostly in the direction of recoil)

I guess the first thing to do would be to estimate the acceleration of the head. This is where you would get an injury, if the acceleration was too high. Really, there is only a couple of frames with the head getting hit. I don't think I can get that from video. But I can get it, oh yes, I can. All I need from the video is the recoil distance. Let me say that the head recoils a distance of 0.2 meters. The other thing I need to know is the final speed of the melon. No clue here. Let me just say that it is going half as fast as it was when it hit (the pieces of the melon are still moving after the collision).

Here is a diagram of the melon at the beginning and at the end of the collision:

Since everything is in the same direction, I can use the scalar-kinematic equation:

Using an initial and final velocity of 15 m/s and 7.5 m/s as well as a distance of 0.2 meters, I get an acceleration of 422 m/s² (oh, this is the average acceleration). This is about 43 g's. Clearly enough to smash the melon. What about the head? Does that mean the head had the same acceleration? No. First, it has a different mass. Second, it is connected to the rest of the body so that there are other forces on it.

Perhaps with a better quality video, I could get a little more detail.

rallain Thu, 09/09/2010 - 09:37

Tags

Based on the way the head deflected, I think there was actually a second watermelon from over on the grassy knoll.

Seriously, though, this woman has a possible concussion, and they didn't halt filming to get her medical attention?

Kurt, that was my thought as well. I've never watched the show - in fact, I've never watched any so-called "reality show." I'm sure participants have signed onerous assumption of risk forms and waived all rights but this smacks of gross negligence. It's hardly conceivable that she doesn't have at least a concussion based not only on her statements of blurred vision and not being able to feel her face but on Rhett's analysis. I'm sure that the attorneys looked it over before letting it air. I wonder if this came from a broadcast or if it was a bootleg?

Yet another example showing that the human body is pretty tough. That watermelon never had a chance.

One detail, Rhett:
That rubber tubing slingshot is essentially a spring, so you shouldn't be expecting a parabolic fit with constant a.

Regarding the likely concussion:
No court could ever find the hostess/actress negligent because it would first have to be shown that she is expected to know anything that isn't in her script. The producers, on the other hand, had better hope they have a medic rushing to the set in panic mode.

So, she has a possible unassessed concussion, and they're exposing her to a *second* blow to the head?! Giving her a few minutes to see how she does is one thing, but risking a second impact?

I agree with stripey_cat. Liam Neeson's wife fell backwards and bumped her head (seemed very minor compared to the watermelon!!). She walked away laughing about it...by nightfall she was brain dead!! The contestant (Claire) said she had a headache and "couldn't see straight"...it could have been caused by broken blood vessels already putting pressure on the brain. They definitely should have checked pupil response to say the least. What about something BEFORE this happened...no offer of a bike helmet-face guard?!? Nothing?
Epic Fail!! I'll NEVER watch this show!! Do they think we're THAT stupid?
Here's the link about Liam's wife and her fall at the beginner's slope:
http://www.imdb.com/news/ni0714386/

I was so caught up in the disbelief of their negligence of her welfare that I forgot to say... Thank you Rhett for doing the math on this, I wondered about the speed of impact when I saw the blurred photo. I wanted to add something, the rebounding of the brain inside the head due to speed of impact and secondary impact- head vs. ground (behind her).
Rhett wrote:"This is about 43 g's. Clearly enough to smash the melon. What about the head? Does that mean the head had the same acceleration? No. First, it has a different mass. Second, it is connected to the rest of the body so that there are other forces on it."
The human skull is a vessel for the brain, a jelly-type substance, which recoils within the rough interior of the skull cavity many times after initial impact resulting in abrasions, etc. There is also the secondary impact of the head hitting the ground at almost as great a speed... and the factor of the object (watermelon) being small and spheroid as compared to an oblong-shaped watermelon which would have broken more easily upon impact, releasing some of the force compared to the smaller one. I'm amazed she's alive and can still see and hear. (as far as I know). Thanks for your awesome work and website, Rhett!! You have a great way of explaining things for us. Hope you know you really are appreciated.

Rhett,
Maybe you've answered this question, but I was wondering what software you use to make your diagrams....

@John,

I use Apple's keynote software to make the diagrams and then I just take a screen shot of it to make it a jpg.

Rhett,
Do you use LaTexIt to typeset the labels?

@John,

Right - LaTexit

Happy g day

rallain — Wed, 08 Sep 2010 10:36:29 +0000

Happy g day

Actually, it should be called Happy "Magnitude of the local Earth gravitational field" day. You know, 9.8 N/kg on September 8 (9/8). Get it? Well, the idea was for the physics students and faculty to build some stuff to do outside - projectile motion type stuff. Well, we had the idea a while ago and then kind of forgot about it.

In order to just get something done, I set up the "shoot the falling target" demo. (previously known as shoot the monkey). Here is a quick video demo (seriously - first take too).

What is going on here and what does this have to do with g? Well, it doesn't really have anything to do with g, but it is a cool demo (meaning this demo would still work on the moon). The basic idea is that you aim a projectile launcher straight at a hanging target. When the ball is launched, the target drops and the ball collides with the target in mid-air.

Why does this work? Let me start with a diagram.

I guess it is clear, but the vector v₀ is the initial velocity of the ball aimed at an angle θ at a target that is a distance s horizontally away and a height h above the launcher. But why do they hit? Let me start with the ball. (here is a quick projectile motion review) The ball's motion can be broken into an x-direction motion and a y-direction motion with the following initial velocities:

Two quick notes: I am using v₀ to represent the magnitude of the initial launch speed. Also, the x-velocity does not change (no forces in the x-direction) so that I can just call it v_x instead of v_x0 (of course, the y-velocity does change). Using those velocities, I can get position-time functions for both directions.

There is the "g"! Also, I am assuming the ball launches at time t= 0 seconds from a position x₀ and y₀. Now, what about the target? The target also starts falling at t = 0 seconds, but its initial position is (x₀ + s,y₀ + h) as seen in the diagram. There is no x-direction motion for the target, so I can just write:

I am calling y_m is the y position of the target as a function of time. The target's initial velocity is zero. First question: what time will the ball be at the x-coordinate of the target? Going back to the function for the x-position of the ball,

And what will be the vertical position of the ball at this same time?

What about the target? Where will the target be at this same time?

Notice that the only difference between the y position of the target and the ball is that the ball has a "s tan(θ)" where the target just has an h term. Oh but wait. Look back at the original diagram and you will see that:

What does this mean? This means that at the time when the ball reaches the x-position of the target the ball and the target have the same y-position. If two things are at the same place at the same time, they hit. Boom.

Notice one cool thing - the value of the magnitude of the initial velocity does not matter (unless the ball hits the floor before it gets to the target). The only important thing is that the ball is aimed at the target. This means that θ for the velocity vector is the same θ for the geometrical set up of the target.

Wait! There is more! How about a nice python-generated graph? This is pretty simple to set up really. In python, I will model the shot ball and the falling target.

That is with a launch speed of 6.5 m/s. What if I increase the speed to 8 m/s?

You can't really see that the two paths cross at the same time. Let me draw fewer points.

There, that is with a time step of 0.1 seconds. The points are numbered and you can see that the two points labeled 4 are right next to each other.

That is it for g-day. I will have bigger plans for next year.

rallain Wed, 09/08/2010 - 06:36

Tags

I also love the shoot-the-monkey demo, and your demo of it was well executed. The huge arc the projectile takes (and hitting just before it falls out of frame) adds to the drama.

There should be some simple way to explain this in basic principles without any trigonometry, no?

Like earth's gravity causes constant acceleration, so what you see in your earth-based lab would have to match what would happen in a zero-g lab as observed by someone in a neighboring spaceship that's accelerating. Which then makes it pretty obvious that if the launcher is pointed at the monkey...

Or something about the linearity of something or other?

@AC,

I guess you could describe this in the accelerating frame of the falling objects. In that case, the target would stay at the same relative position with respect to the launched ball.

More basketball analysis

rallain — Fri, 20 Aug 2010 06:21:40 +0000

More basketball analysis

Reader Jorge has also looked at these amazing basketball shots. (here is my last basketball analysis) Jorge claims that at least one shot seems fake. He is referring to the following video (at around the 2:20 mark).

ARRGH Ok, new plan. For some dumb reason, youtube won't let me embed this video. Well, here is a link - Amazing Basketball Shots: The Legendary Shots 4 (at least I can link to the right time). It is even dumber that you can't embed it, but youtube gives you the download option. Oh well.

Let me tell you the part that Jorge has an issue with. This guy on a ladder throws a basketball through the hoop. The ball then bounces back up and through the hoop again. Here is an annotated screen shot.

So, what is the problem? Jorge claims that there is evidence of video-fakery - primarily by looking at the ball and the goal-pole. He also claims that the ball would not bounce that way if it wasn't spinning. So, what do I think? First, I tend to think things like this are real. Maybe someone would go through the trouble to fake it, but who knows. Could something like this be faked? I assume so - probably by shooting the ball through and then later bouncing a ball into the goal and combining the two.

First let me address the spinning-bouncing part. I think Jorge is correct in that a non-spinning ball on a flat surface would not bounce back. However, I am not certain the ball is not spinning. The video is not clear enough to show the spin. I would assume there would be some spin from the way he threw the ball. Enough about the spin.

Ok, is there anything I can look at to see if this particular clip is real or fake? Fortunately, this clip is a good one to analyze.

The camera is stationary
The camera is perpendicular to the motion of the ball
The camera is far enough away (at least it seems) so that there are no perspective problems

It would be nice if the video was in a little higher resolution, but I guess it is ok. Also, since the background is simple and stationary, this makes the great candidate for the autotracker feature of Tracker Video analysis.

In this analysis, I picked the height of the goal to be 3 meters. This is likely wrong because I get the wrong value for the acceleration while the ball is free falling. Oh well - that is ok. The goal could really be at any height. Here is a plot of the ball after it goes through the goal a second time. The nice thing about this is that it shows a couple of bounces.

This is a plot of the vertical velocity after it goes through. The slope of the three lines is around the same value (which is good - because they are all cases of free fall). What I want to get from this is an estimate of how the speed changes after a bounce. The first bounce hits at about 7.5 m/s (going down) and leaves at about 5.3 m/s going up. For the second bounce, it hits at 5.3 m/s and leaves around 4 m/s.

The ratio of the speed before and after the bounce should be a constant. This constant is called the coefficient of restitution. Let me calculate the coefficient (C_R) for these two bounces.

Ok, so it is in the 0.7-ish range. Now, what about the bounce after it went through the goal the first time? Here is a plot of the velocity of the ball.

This doesn't look too great. The velocity after the bounce looks fine. Before the bounce, I think there was a problem with the ball moving fast. This means that there aren't many data points to look at. How about I look at position data instead of velocity data?

If I fit a quadratic function to the position data, it mostly agrees that the velocity before impact is around 13 m/s. The velocity after the bounce is 8.5 m/s. This gives a coefficient of restitution of:

The coefficient seems a little different. Is this different enough to say that the before motion and the after motion don't go together? I am not sure. That collision with the floor seems to be different than the other two bounces. The coefficient of restitution can't possibly be an always the same constant for a basket ball. Imagine shooting it a mach 1 speeds. Would it bounce off with 0.7 times the original speed?

Where does this leave this? I know if you look at individual frames, some things can look funny. But I am just not enough of a video compression expert to really comment on those. So, I guess I will leave it where I started. There is nothing that says it has to be fake. I am sure you could get a basketball to do that motion.

Pre-emptive comments:

Why do you do this? Why do you analyze some video and at the end say "well, it could be real or fake?" - answer: I am really looking for some piece of evidence that says it HAS TO BE FAKE (or probably)
So, are you saying it is fake or not fake? answer: see above.

rallain Fri, 08/20/2010 - 02:21

Tags

coefficient of restitution

analysis

Actually, it looks to me as if the driveway is slightly raised compared to the front door, and that there is a slanted seam at just about the point the ball hit. I suspect that is what gave it the back-momentum it needed.

While I can't comment upon the authenticity of the referenced clip, such things are easily faked. I humbly submit the following as a potential explanation:

http://www.youtube.com/watch?v=UbvngiztFVk
http://www.youtube.com/watch?v=rqAt2akPHJ8

Again, just because it COULD be faked, doesn't mean it IS faked. I withhold judgment until the YouTube poster releases the unedited footage showing a brazillion failed attempts.

@Aaron,

You are correct. Thanks for posting those links. (I have been burned before - hint: giant water slide jump)

When I looked at the actual video, it is clear that the garage floor on the right is maybe one brick higher than the one on the left. The driveway slopes down from the edge of the garage door to the side door. This is hard to see in your frame grab because of the line you drew.

Estimate that angle and see if the bounce angle is more likely. It is also more reliable than the familiar problem of dribbling on a joint.

What is suspicious is the nearly constant downward v.

In response to Ahcuah, take a look at the shadow when the ball hits the grounds. Any variation in the angle of the surface from the horizontal is negligible. Also, any anomaly on the surface that is large enough compared to the basketball to significantly affect its trajectory should be clearly visible.
In response to CCPhysicist, I don't think that a constant downward velocity is suspicious for the initial throw. Is 13 m/s an unreasonable terminal velocity for the basketball?

Pouring tea in a plane - upside down

rallain — Tue, 17 Aug 2010 18:19:54 +0000

Pouring tea in a plane - upside down

Let me start with the video. Here is a guy flying a plane in a barrel roll and pouring some tea at the same time. Talk about multitasking.

How can he pour upside down? Well, there are two ways to look at this. First, I can look at this in the frame of the plane. For this case, I can invoke the fake force - centrifugal force. Oh yes, I am going to do it. You probably remember all your physics instructors warning you to never ever do this. Well, they say that because they are afraid you will do something bad with it. Here, I will only use the centrifugal force for good.

What is the centrifugal force? Well, suppose I am in a rotating frame and I want to pretend that it is not rotating. To do this, I will need to come up with some fake forces to account for the behavior of objects in this frame. A fake force is one that is not based on fundamental interactions (most forces you see are electromagnetic forces and some are the gravitational force). Here are some previous posts about fake forces if you are still interested.

So, I am in the frame of reference of the aircraft. The aircraft is doing a barrel roll - meaning that it is moving both forward and in a circle perpendicular to the main direction of motion. The center of this circle is outside of the plane. First (to make sure we agree on the situation) here is a diagram of the plane doing the maneuver.

Note: I am not a pilot except for in Microsoft Flight simulator - in that I landed a 747 on a tiny runway. Ok - back to the aircraft. Let me draw the interior at say the instance where it is sideways.

Here the "F-net" force is the net apparent force in this frame. So the red ball would kind of fall if released. At the top, as long as the fake centrifugal force is greater than the gravitational force, the ball will "fall" up. The magnitude of the centrifugal force would be:

It is important to note that the "v" in this expression is the velocity as it moves around the circle - not the total or forward velocity.

Now on to the other way to look at this problem - from outside the aircraft. In both the frame inside the aircraft and outside, there must be an agreement about the motion of the ball (or "free falling tea"). Here is a quick video of a vpython simulation. A couple of notes:

The red ring represents the aircraft (you are looking at it "head on")
The blue ball is some object in the aircraft.
For the first part of the barrel roll, the ball is being supported by something - maybe it is Harry Potter with his invisible cloak on.
After that time, the ball is released. Notice that the path of the ball after that point is parabolic.

Ok, now you can watch the simulation (sorry for the poor quality - I will have to work on that)

So, from the outside, after the ball is released, it moves towards the "floor" of the plane which happens to be in the up-ish direction.

One final note (but is it ever really 'final'?) This is very similar to one of my all time favorite demos - the water on the serving tray suspended by a string.

rallain Tue, 08/17/2010 - 14:19

Tags

Is that why rotating sections in space stations/ships provide artificial gravity?

Dale: yeah, this has been invoked for at least 50 years to get around the biological problems of long periods of microgravity etc.

I have to take this opportunity to give a massive cheer for Bob Hoover, one of the most incredibly skilled pilots ever. Anyone who flies will sing his praises.

Well it makes sense is some sort of way. Never thaught of it myself but bob hoover made a great video. Well I have a new topic for class next week! Thanks for the share!

For this case, I can invoke the fake force - centrifugal force. Oh yes, I am going to do it. You probably remember all your physics instructors warning you to never ever do this. Well, they say that because they are afraid you will do something bad with it.

You mean like Dr. No in this XKCD cartoon?

Thank you Eric Lund. I was going to cite the same XKCD strip. It's the last word on centrifugal force.

More on turning and braking

rallain — Mon, 16 Aug 2010 10:49:37 +0000

Tags

> Is it possible you could turn right then left then brake? Maybe.

But it will have a longer stopping distance than just braking. See my comment to your last post - you can show this is the best strategy without any calculation (assuming your starting velocity is normal to the wall and the wall is infinitely wide).

> But, I am surprised that turning 90 degrees is not the largest stopping distance.

It's an interesting result, but easily understood.

The more you've turned (i.e. the larger the angle between your velocity vector and the normal to the wall) the more "efficient" turning becomes: in the limit that you're moving parallel to the wall, 100% of the acceleration of turning is normal to the wall.

So if you're already at a large angle (having turned, say, 70%) it's now better to turn (where most of the acceleration is going into reducing the normal vector to the wall) than brake (where most of the acceleration is NOT reducing your velocity along the normal vector).

I tried a little bit of back-of-envelope math, and it put the "tradeoff angle" happening at the solution to the equation (1-sin(x)) = (cos(x))/2, which is around 37 degrees. This is the angle of travel at which it's better to turn rather than brake, and does NOT include the braking vs. the turning required to get to that angle (assuming starting normal to the wall), but with a little bit more work you should be able to turn this into your numerical result.

Ok, what about a 180 degree skid and accelerating, with smoking tires and a loud pounding bass line, and a supermodel riding shotgun, twins (with puppies) in the back seat, and a MacGuffin in the trunk? Does it make a difference if you are Bruce Willis?

It's fairly obvious that the optimal solution is to always have 100% of your deceleration be normal to the wall. Let's break your force into two parts: Normal Force and Parallel Force, and similarly normal/parallel displacement and velocity. It's fairly simple to see that you will stop approaching the wall when (NF * ND) + 1/2 * m * NV^2 = 0; parallel force and motion is entirely irrelevant.

If you start moving straight towards the wall, 100% of force being away from the wall is deceleration. If you don't, it's turning, because the optimal solution doesn't involve any change in PV, and in fact your PV should remain constant over the entire period of the turn.

So, at any given angle, how much of your force will be turning, and how much will be braking? Well, the turn vector will be a force at 90 degrees from your current course, and the deceleration will be a force at 180 degrees from your current course, and you want them to add up to a force which is directed away from the wall, your braking winds up being sin(approach angle) * coefficient of friction, your turning winds up being cos(approach angle) * coefficient of friction.

Oh, and, since the normal force is constant, your path when using an optimal braking solution when coming in at an angle will be a segment of a parabola.

I'd agree with #3 that, in the case with a barrier of infinite width, the best case is the one in which all of the force is exerted normal to the wall.

Of course, in the more realistic case of an object with finite lateral extent, it may be better to swerve than attempt to stop. Of course, this depends heavily on the width of the object to be avoided. In the limit of an infinite object it should reduce back to the results you are getting here.

I suspect if you look hard enough an autos motions can be decomposed into a few basic types, just like a planes motions are in Stick and Rudder. A plane basically can fly level, climb, glide (decrease altitude) and turn, everything else is just a superpostion of these. With these motions you can get planes to slip and skid (rudder versus aileron motion I don't get the details) and stall and spin (bad news) Unless you assume an asymettric auto, then a car can accelerate, slow, or turn. Again its just a super position for the more complex motions. The symmetry assumption is to make left and right the same otherwise you take turns to left turns and right turns.

You know there is one other option no one mentioned: turn and accelerate. It is well known that you can get more centripetal force from the drive wheels when racing on surfaces like dirt and ice than you can from the lateral grip of even the most expensive tires.

Now in this case you don't turn the motion of the car, you turn the car relative to its motion so the nose is pointing somewhat towards the center of the turning circle followed by the center of mass. The advantage of this is tied into the fact that the coefficient of friction is not a constant independent of the motion of the tire relative to the surface. However, I believe most of the analysis remains unchanged. In this last case, the shortest stopping distance would be found by snapping it around in a 180 and flooring the gas rather than the brake.

Some more info on basketballs

rallain — Fri, 13 Aug 2010 10:10:57 +0000

Some more info on basketballs

You know I have trouble letting stuff go, right? I am still thinking about these crazy long basketball shots. Here are some more thoughts.

Really, there are two things I am interested in. First, commenter Scott Post suggests that the drag coefficient might be around 0.25 instead of 0.5. I don't know. For the discussion before, it doesn't really matter. My point was to see a numerical model for a falling ball would be similar to the time and distance from the video. Changing the drag coefficient to 0.25 gives values that are still close to the video. So, I still think the video is real.

The other thing that I would like to explore is the range of launch angles and velocities for a person throwing a ball. This would be important to have a feel for the spread of initial values so that I could estimate how many times you would have to try a shot to make it.

After a short search online, I found two interesting articles. One of them I know you can read - the other you might only be able to access if you are at an academic institution or if you are a subscriber to the American Journal of Physics. Below I will extract the useful details from these two papers.

The Perfect Shot - Seleh Satti

This pdf paper does not appear to be published in a journal, just online. The author looked at a few shots of a basketball indoors from the same distance away from the goal (5 shots). It seems the main point was to determine if you would need to include air resistance and spin effects in the analysis of this shot. To do this, Saleh used a video camera to capture the 5 shots (one of which was a miss) and then did some video analysis.

For air resistance and spin, the author claims there are not noticeable effects - mostly because there is no horizontal acceleration. It is odd that the vertical values for acceleration were around 9.1 m/s². But maybe this was just a scaling problem.

Here is a table showing the initial velocities for the 5 shots. This can give some idea of how consistent a shooter could be (although it would be nice to have more than 5 data runs).

That could be useful.

Physics of basketball - Peter J. Branczio

This paper is from the American Journal of Physics (didn't I already say that?) and really tries to do a lot of stuff. Part of it covers bouncing of a rotating ball (which is interesting, but not what I am looking for). The author also discusses the kinematics of projectile motion (but not with air resistance). There are some more details about projectile motion for an object of finite size that has to hit a target. This, in particular, diagram is interesting:

Basically, the lower the angle of incidence for the basketball, the smaller the apparent size of the hole. And here is another great diagram showing the range of initial velocities and angles that will result in a successful shot (where it doesn't hit the rim).

Finally, the author compares no-air resistance with air resistance for some cases. The result is that you would have to adjust the initial velocity by about 5% to compensate for the drag.

Where does this leave me?

The problem with both of these papers is that they are for normal basketball shots - not super duper shots, so air resistance isn't such a big deal. I would really like to have an experimental value for the drag coefficient of a basketball. Probably the best bet would be to get a nice video of a basketball traveling very fast. From this, I should be able to get the coefficient (I will put this on my to-do list).

The second paper was very detailed, but it approached the problem from the wrong direction. It said "what initial conditions would you need to hit the goal". I want to know what variation a player would have in throwing a ball. Oh well, I think I can get this data myself also.

rallain Fri, 08/13/2010 - 06:10

Tags

What about the backboard? I'm not much of a basketball player, but I do recall that it's supposed to be easier to make the shot if you bounce it off the backboard.

Well, I found that a different basketball shot that The Legendary Shots took was digitally manipulated, so it makes all their shots questionable. Take a look at http://jorfer88.blogspot.com/2010/08/irrefutable-evidence-that-legendar… .

Turn or go straight? Quick!

rallain — Thu, 05 Aug 2010 14:07:24 +0000

Turn or go straight? Quick!

This is a classic problem. You are in a car heading straight towards a wall. Should you try to stop or should you try to turn to avoid the wall? Bonus question: what if the wall is not really wide so you don't have to turn 90 degrees?

Assumption: Let me assume that I can use the normal model of friction - that the maximum static friction force is proportional to the normal force. Also, I will assume that the frictional coefficient for stopping is the same as for turning.

Stopping

I am going to start with the case of trying to stop. Suppose the car is moving towards the wall at a speed v₀ and an initial distance s away from the wall. Diagram time:

This is a 1-d problem. So, let me consider the forces in the direction of motion. There is only one force - friction. Now - you might be tempted to use one of the kinematic equations. Well, I guess that is just fine. The following equation is appropriate here.

Really though, I would think - hey distance. That means use the work-energy equation. It gives you the same thing though - essentially. Since I already started with this kinematic equation, let me proceed. In the direction of motion, I get:

Putting this into the above kinematic equation (with the change in x-distance as just s). Oh, note that I am using the maximum static frictional force. I am assuming that this will be the shortest distance you could stop. Also, I am assuming that I the car stops without skidding.

There you have it. That is how far the car would need to stop. Quick check - does it have the right units? Yes.

Turning

Now, how far away could the car be and turn to miss the wall? Really, the question should be: if moving at a speed v_o, what is the smallest radius turn the car could make?

For an object moving in a circle, the following is true:

Here is my review of acceleration of an object moving in a circle. Key point: I said I could have used work-energy for the stopping part. I could NOT have used work energy for this turning part (well, I could use it but it wouldn't give me anything useful). There are two reasons why the work-energy principle won't do you any good. First, the speed of the car doesn't change during this motion. This means that there is no change in kinetic energy. Second, the frictional force is perpendicular to the direction of motion so that it does no work (we can discuss work done by static friction later).

Back to the turning calculation. I know an expression for the frictional force and I want the radius of the circle to be s. This gives:

And there you have it. If a car is traveling at a certain speed, it can stop in half the distance that it would take to turn.

I kind of like this result. Long ago, I took a driving class. You know, to learn how to drive. One think stuck in my mind. While driving, something came out in the road in front of me (I can't remember what it was). I reacted by swerving just a little into the next lane. The driving instructor used that annoying brake on the passenger side (that he would sometimes use just to show he was in control - I was going to stop, but he didn't give me a chance). Anyway, he said "always stay in your lane". He probably said that because he was so wise in physics even though he did smell funny.

Oh, it is probably a good idea to stay in your lane not only for physics reasons but also because you don't want to hit the car next to you (unless you are playing Grand Theft Auto - then that is encouraged).

Another question

I wonder if you could stop in even shorter distance? Is stopping the best way? Is there some combination of stopping and turning that could work?

Let me try the following. What if the car brakes for the first half and then turns for the second half. Would it hit the wall? First, how fast would it be going after braking for s/2 distance? The acceleration would be the same as before:

Using the same expression for the stopping distance from above, I get:

And this makes sense. If the car is stopping just half the distance, then it should have half the kinetic energy (which is proportional to v²). Ok, so if that is the new speed, what radius of a circle would it be able to move in? Again, using the expression from above:

Using this with half the distance - the total distance it would take to stop would be:

This is still greater than the stopping distance for just braking (which is s). But, did I prove that just stopping is the shortest distance? No. Maybe I just convinced myself to stop for now.

Bonus

Here is a short bonus. Let me show that the work-energy principle is the same as that kinematic equation I was using. So, a car is stopping with just friction. The work done on the car by friction (and I can do this if I consider the car to be a point particle):

The work-energy principle says this will be the same as the change in kinetic energy of the car. If the car starts at a speed of v₀ and stops at rest then:

See. Same thing.

Homework

How wide would the wall have to be so that it wouldn't matter if you brake or turn? Either way you would miss?

rallain Thu, 08/05/2010 - 10:07

Tags

One of the things I remember being drilled into me during driver training was brake and avoid.

There's an interesting dynamics aspect to this, in that braking results in a transfer of the car's weight forwards, which gives you more traction to make the turn. In the absence of ABS, slamming on the brakes will result in your wheels locking up and thus a complete inability to steer (not to mention, an increased stopping distance).

What about hard left, then brake? After all, in America, that would get the driver's side away from the wall, so that if your stopping distance is too much, you at least avoid a head on collision, and provided you have no passenger, there shouldn't be serious injury. Because if s> the distance between the car and the wall, you really need to think in terms of minimizing damage.

For that matter, if you hit the wall at an angle instead of head-on, you'll slide along it instead of stopping instantly. This should reduce the deceleration forces acting on you, decreasing your odds of injury. So it seems to me that combined steering and braking is the way to go.

Don't forget the crumple zone you have if you hit front on

In Sweden you learn to break and swerve. Reason being, your normal obstacle (a moose, a human) is not all that wide, and the road is pretty likely to be empty apart from yourself. If there's lots of traffic, it's unlikely that there'd be a static obstacle on it after all.

There's a secondary consideration too. If you just swerve and fail, then you're likely to hit the object at close to your original speed. And as speed is by far the most important determinant of injury and death, that's a Bad Thing.

On the other hand, obstacles are very rarely really wide. Anything remotely likely to show up on a street is pretty narrow - a moose, a car or something like it. So once you're slowed down a bit chances are still pretty good that you'll be able to avoid it. And if you don't, you'll still hit at much lower speed than if you just swerved and failed.

@Samantha,

Turn and then brake? Why didn't I think about that? I did brake then turn. Hmmm.. I will have to do a follow up post.

if you have a choice of a head on collision with, say an oncoming car, or swerving a bit so it isn't head on, choose the swerve option.

your momentum can be broken up into components parallel and perpendicular to the other objects motion. by avoiding headon, you can decrease the parallel component by the cosine of the angle, and thus decrease the magnitude of your change in momentum, the acceleration and thus the damage.

If your wall is infinitely wide (as stated in the original problem), you can show that braking is always the best option if you want to avoid a collision with the greatest car-wall separation (assuming the car is a point).

Just decompose your velocity vector into the component normal to the wall and a component along the wall.

If you turn (and avoid the wall) or do some combination of braking and turning:
1) the component normal must decelerate to zero at the point of closest approach
and
2) the component along the wall will increase to something nonzero.

If you just brake, you still have to do #1, but you avoid any forces required to achieve #2. Thus braking requires less total force.

So, for the infinite wall (and a point-mass car) braking along a straight line is superior to any braking/turning combination.

For the finite wall (or moose, as discussed above) it would probably require some algebra.

I agree with break and trun. With that, how fast would your speed have to be to flip your vehicle during your turn (depending on weight, center of gravity, width of tires, etc.)?

A lane change can be done in significantly less distance than either of the two extant options, but that will not work in the classic homework version of this problem where the road is completely blocked but there is a side street open if you turn. This works because you don't turn 90 degrees. Not even close. However, see my final observation below.

Minor detail in your solution: The standard problem assumes the same coefficient of friction for braking and turning, but this is only an approximation. Most tires have more grip under braking than when turning, which favors the braking solution even more.

What Anonymous Coward says is a result of what is known as the "friction circle" in racing. You trade sideways acceleration for fore-aft acceleration, which is why you brake and then turn ... leaving out all sorts of fine details. (Tires are complicated. Kinetic friction is a bit more than static friction as long as the slip is a small fraction of the velocity, then falls off rapidly once the tire is not rolling at all. This applies to both forward motion and the "slip angle" when cornering and is significantly different, depending on tire design, when cornering. The "friction circle" is usually an ellipse with the coefficient bigger for braking as noted above.)

The coefficient of friction when rolling, or (even better) rolling and slipping slightly, is bigger than when the tire is sliding sideways. This means that tossing the car so it slides sideways is a really bad solution and will result is significantly larger values for the variable "s" in your solution.

All of this ignores vehicle dynamics and traffic. If you are in the right car and are fully aware of the space around you, a lane change is the best way to avoid a problem in the road ahead. If you are not fully aware of the space around your vehicle, changing lanes can make things worse, and even skilled drivers are not always paying full attention to the road. Hence the driving instructor advice to stay in your lane. Worse, you might be in a van or SUV where sudden turning movements, particularly lane changes, with under-inflated tires can cause the vehicle to roll. Even passenger cars can get in trouble this way if one tire is off the pavement, which is why you should have been taught to slow down in a straight line before pulling the car back on the pavement from an unpaved shoulder.

@comment 1- You can still steer when braking, independent of whether or no the car has ABS. It's called the Emergency Brake, and in most vehicles it is attached only to the rear wheels.

I see I've been beaten to the Brake and Turn. I have done just that in a car- E-brake and a turn so that I do a complete 180. That would seem the best choice- and the distance needed to stop is far less than braking alone.

@11 - Unless you're a trained stunt driver, I wouldn't advise yanking the hand brake and then turning, because you're going to end up locking up the rear wheels and then going into an uncontrolled skid/slide.

But sure, it will look really cool.

@11 - The only advantage to doing a 180 is that you hit the wall going backwards. Your stopping distance will be greater because the coefficient of friction is less than with threshold braking or modern ABS while going straight.

The disadvantage might be that you kill the kids in the backseat because cars are not designed to crash that way.

Sure would make a great Mythbusters episode, however.

Visual and MatplotLib - holding hands at last

rallain — Mon, 19 Jul 2010 10:28:03 +0000

Visual and MatplotLib - holding hands at last

(alternate title: how to make pretty graphs in vpython)

I am happy. Finally, I can use the visual module in python (vPython.org) and plotting with Matplotlib. Maybe this isn't such a big deal for many of you, but for me, it never worked until now.

In the past, I blogged about plotting in vpython vs. matplotlib. My conclusion was that it was easier in vpython, but prettier in matplotlib. So, why not just use matplotlib? There are a couple of things that make vypthon very attractive.

Vectors. Vpython has a built in vector class (or function - I don't know what I am talking about). There are also things like dot-product, magnitude, normal vector. With matplotlib, I would have to use arrays to represent vectors. It is just a little more clumsy.
Objects. In vpython, I can make an object ball=sphere(). Then I can do stuff like calling the mass ball.m and the momentum ball.p.
3d. If you want to make a visual representation of what is happening - basically you are there.

If you look back at one of my zombie posts, I actually did the calculation twice. First I did it in vpython, then I redid it with matplotlib to make a pretty graph. Now, I don't have to do that.

Setup

First, what was the problem. I found out from the visualpython-users mailing group that the problem was with my installation of matplotlib. I had used the Enthought python distribution and this was the problem. Vpython and Enthought were doing things different with the installation. Let me just leave it at that.

To fix this, I manually installed matplotlib (apparently only the older version works - 0.99.1.1). Boom. That did it. Now I can load both visual and pylab modules at the same time. If you are using a Windows computer, your fix might be easier (I am on Mac OS X). Reports say the pythonxy project has all this stuff together already.

There is still one problem. If you try to run a visual display window and a matplotlib graph at the same time, bad things can happen. Sort of like crossing the streams in Ghostbusters.

Making graphs

Let me go back to the same example I used when talking about matplotlib vs. vpython, but I will make some modifications. Here is my program:

And here is the pretty output. Shiny, right? Well, way better than the normal vpython graphs (sorry vpython, but it is true)

If you want to go back to vpython output, just comment out the scence2.visible=false line. Also comment out all the matplotlib stuff at the end. Boom, there it works again.

Let me point out one final difference between plotting in matplotlib and vpython. In matplotlib, you have to collect all the data and then plot it. In vpython, you can plot one data point at a time as you calculate this stuff. The nice thing about the vpython way is that you can see how the plot develops over time.

rallain Mon, 07/19/2010 - 06:28

Tags

numerical calculations

ploting

pylab

vpython

I believe you can plot data points one at a time in matplotlib. I assume my tabbing will be mangled, but run this from within ipython:

import pylab

pylab.figure()
for a in range(10):
(tab)b = a**2
(tab)pylab.plot([a], [b], '.')
(tab)pylab.show()
(tab)print "Hit enter to continue..."
(tab)raw_input()

Why not use Gnuplot? http://www.gnuplot.info/ I assume it's a little easier than both vPython and Mathplotlib.