“A theory is a supposition which we hope to be true, a hypothesis is a supposition which we expect to be useful; fictions belong to the realm of art; if made to intrude elsewhere, they become either make-believes or mistakes.” -G. Johnstone Stoney
It's been another exciting week here at Starts With A Bang! This coming Thursday, I'll be speaking at Jacksonville University in Florida; if you're around that area come and say hello! Before we get any further, I'm pleased to announce that thanks to two very generous new Patreon donations from Ryan Schultz and Samir Kumar (shout-out!), we've now hit the next rewards tier on my Patreon campaign, meaning that we'll be commissioning the creation of the most scientifically accurate, beautifully illustrated history-of-the-Universe poster of all-time! Come be a part of our Patreon if you're not already, and get in on the rewards!
We've also, as always, had a slew of fantastic articles come out this past week. If you've missed anything, check them all out below, including:
- Does dark energy mean we're losing information about the Universe? (for Ask Ethan),
- The nearest supernova of our lifetimes turns 30, and still shines (for Mostly Mute Monday),
- Recent Claims Invalid: Emergent Gravity Might Deliver A Universe Without Dark Matter (by Sabine Hossenfelder),
- How NASA's James Webb Space Telescope will answer astronomy's biggest questions (a live-blog event),
- 7 ways Earth would change if our Moon were destroyed, and
- NASA's MAVEN discovers how Mars lost its atmosphere.
You've had your say in the comments section, and now it's time for me to call out the ones that I have the most (or most important) things to say about them in this edition of our comments of the week!
Outlined in light blue, giant collections of galaxies can be divided up into superclusters. But this classification doesn't make superclusters real. Image credit: The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède, Nature 513, 71–73 (04 September 2014).
From Paul on how much we still don't know: "It’s humbling to read such articles and realize how little we understand of everything that is around us……"
I think this is one of the most important things to recognize about science. Whenever we seek to answer a question, scientifically, it demands that we gather new data, make new observations or perform new experiments. We need additional degrees of precision and accuracy, and more information to decide on what the correct outcome/answer is. But even when we obtain them, it raises more questions. What's there at the next significant figure? Where does the current explanation break down? What's the next fundamental question to answer? And what additional puzzles arose because of the new information we have?
Our total knowledge about everything may be fundamentally limited, but we haven't hit those limits yet. In fact, we're not even close.
An artistic rendition of Benjamin Franklin drawing electricity from the sky at the Philadelphia Museum of Art. Image credit: Benjamin West, c. 1816.
From Omega Centauri on Ben Franklin: "Franklin’s kite experiment is not something you should try at home. I’ve heard that people have been killed trying it. Franklin was lucky."
Of course you shouldn't fly a kite in a lightning storm; Beavis and Butthead once did a whole episode about it. The legend of Ben Franklin -- that he flew a kite in a lightning storm grounded by a key and some silk -- and the likely actual story, that he tied a kite to a metal cage, are vastly different.
Don't try and attract lightning to your body, kids.
Heat-trapping emissions (greenhouse gases) far outweigh the effects of other drivers acting on Earth’s climate. Source: Hansen et al. 2005, Figure adapted by Union of Concerned Scientists.
From Denier on climate science and climate scientists: "I laughed out loud when I read this. Of course climate scientists are real scientists and I’m blatantly trolling when I say otherwise."
I will always take you at your word, so that makes me a very easy target for trolling. Just FYI. My other option is to selectively ignore what you say, which isn't really my modus operandi. Recently, Tucker Carlson had Bill Nye on his program and asked him, what percentage of the observed warming comes from human activity. The above figure, although it's a decade old, gives the approximate answer: around 125%. The light-blocking and light-reflecting properties of other human activities -- like pollution, additional cloud cover and jet exhaust -- actually help with the warming. It's observations like this that make geoengineering even possible; there are human activities we can perform that reduce the amount of incident sunlight.
The question is what's the optimal path forward? And this is something we can only model or simulate. There may be only one answer for orbital mechanics, but try simulating a more complex system -- like the large-scale structure of the Universe -- and each independent simulation will give you different answers in the details. Because you can't simulate something that requires more computing power than you have, so you make simplifying (and wrong) assumptions: that dark matter particles have masses of 10^9 suns; that the Universe acts like a mesh far away and individual masses act like particles up close; that the gravitational interaction "turns off" when you're too close; etc. Simulations are incredibly useful, but they are only good to the limits of the simulations.
And yes, there are bad scientists and unethical actors anywhere you go, and climate science is no different. We're not going to get anywhere arguing over who is smarter, more gifted, etc. The point is that this is robust, reproducible science, with quantifiable errors and uncertainties that lead to an overwhelming conclusion: humans are the cause of Earth's warming and that the consequences are increasing for the planet. Undark had an interesting piece on the assumptions that the left and right makes with respect to climate science. I make assumptions #2 and #4 from the left and none of the ones on the right. Which ones are you?
The idea that instead of 0-dimensional particles, it’s 1-dimensional strings that fundamentally make up the Universe is at the core of string theory. Image credit: flickr user Trailfan, via https://www.flickr.com/photos/7725050@N06/631503428.
From Naked Bunny with a Whip on what string theory predicts: "I thought the biggest problem with string theory is that you can’t use it to make predictions because there are so many different solutions."
Let me ask you a question: what's the energy contained in empty space? This is something we've recently measured (or perhaps more accurately, inferred) thanks to the discovery of dark energy. People's intuitions told them it would be "zero" for a long time; then they tried to calculate it and got a value that was so large it would destroy the Universe in about a Planck time; then they measured it to be ~10^-120 times the size of that second number. That value is known as the vacuum expectation value (or VEV) of the vacuum.
String theory doesn't have the same unknowns that the Standard Model does: masses, charges, quantum numbers, etc. That's all calculable. But the VEVs of each of the strings? No predictions. You can put in literally anything; they're free parameters. That's where the "so many different solutions" ideas comes in. Because you've taken a hard problem and made it even worse. That's definitely a big problem.
How cosmic inflation gave rise to our observable Universe, which has evolved into stars and galaxies and other complex structure by the present. Image credit: E. Siegel, with images derived from ESA/Planck and the DoE/NASA/ NSF interagency task force on CMB research. From his book, Beyond The Galaxy.
From Paul on doubting the Big Bang: "here’s problem with the “Big Bang idea…..it comes from the observation of dozens of galaxies…..what about the other billion trillion zillion ????????"
So I wrote a pretty well-reviewed book that addresses where the Big Bang idea comes from and how it was verified in chapters 3, 4, 5 and 6. The idea of the expanding Universe initially came from only dozens of galaxies; that number is now in the tens of millions. (Which are the ones we have data for.) The Big Bang idea came as one of many ideas out of that observation coupled with General Relativity, and -- as Denier says later -- was verified and validated by observations of the cosmic microwave background.
It is on much more solid footing than you give it credit for.
Combined X-ray, Radio & Optical Images of Abell 3411 and Abell 3412. Images credit: X-ray: NASA/CXC/SAO/R. van Weeren et al (blue); Optical: NAOJ/Subaru (white); Radio: NCRA/TIFR/GMRT (red).
From CFT on dark matter: "Dark matter is a fudge factor used to prop up failing cosmological assumptions and calculations based on those assumptions..."
Dark matter is a "fudge factor" in the sense that anything indirectly observed is a fudge factor. You could have said the same thing of atoms, of electrons, of the quantum wavefunction or of quarks. The fact that it makes predictions that have been borne out by observations is tremendous in the scientific sense. The fact that it hasn't been detected directly is a constraint on its (unknown, by the way) cross-section with normal matter and itself, not evidence of its absence.
Keep asking questions and learning, though. Eventually, you'll come to the dark side.
This multiwavelength composite shows dust (red), visible light (green), and ultra-hot gas (blue) from ALMA, Hubble and Chandra, respectively. Images credit: ALMA: ESO/NAOJ/NRAO/A. Angelich; Hubble: NASA, ESA, R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation) and P. Challis (Harvard-Smithsonian Center for Astrophysics); Chandra: NASA/CXC/Penn State/K. Frank et al.
Two supernova questions from PJ: "What would cause the SN to form a disk of material from the center of the star (assumed center) with ejected material symmetrically expanding along the objects axes? Why not explode in the form of a spherical apparition?"
Quite simply to your first question: rotation. Rapid rotation means that the equatorial material is less tightly bound to the star and easier to eject into space. We launch rockets closer to Earth's equator for that reason, and the effect is pretty small on Earth. Some stars can rotate at thousands of km/s, meaning any outward "push" preferentially pushes material out along the equatorial plane.
The second question is a big misconception that existed among even supernova scientists until the late 1990s/early 2000s when (surprise!) simulations got good enough: supernovae aren't spherically symmetric! If you start the supernova explosion off-center even by a tiny bit -- whether type Ia or core collapse (type II) -- you get a very non-spherical explosion.
If gravity itself isn't a fundamental force, but rather an emergent ones, many of the mysteries of space and time may have a different solution than the ones we're presently seeking. Image credit: Zoltán Vörös of flickr.
From Axil on emergent gravity: "The growing acceptance of Erik Verlinde’s work..."
STOP. You do not pass go. You do not collect $200. There is no growing acceptance of Verlinde's work, period. Verlinde's work is work in its infancy: it is the beginning of science. In two particular ways, it makes some predictions. One of those predictions was claimed to be falsified; that claim was incorrect. That is what the article states. That is what the article is about. There is no growing acceptance of his work or his ideas. It merely has not been ruled out yet.
The dark matter halo around galaxies could be explained, in principle, by a new type of entropy that's affected by the normal, baryonic matter present in space. Image credit: ESO / L. Calçada.
From Anonymous Coward on Verlinde's work and the true challenge: "Welp, seems that there’s still no word on whether it’s actually going to work for the ultimate test of any dark matter alternative: galaxy cluster and cosmological scales."
This is a big deal. You see, on galactic scales, it's relatively easy to modify gravity (or modify something) and reproduce the observed behavior. But on larger scales, dark matter is the only thing that works. So what about large-scale clustering? Well, it hasn't gotten as much attention, but as entropy changes (grows) over time, the emergent gravity phenomenon that acts like dark matter should grow. Meaning that observations of distant galaxies and clusters and filaments should show less evidence for dark matter, with the first galaxies showing practically none at all.
I believe that if this were put to the test, Verlinde's theory (or at least one of his equations) would be falsified. But no one is taking this approach yet, and I am kind of busy.
An artist's conception (2015) of what the James Webb Space Telescope will look like when complete and successfully deployed. Note the five-layer sunshield protecting the telescope from the heat of the Sun. Image credit: Northrop Grumman.
From MandoZink on JWST, its launch and what it means: "I have been waiting so eagerly for this launch event, complete with all of the magnificent things it would reveal. I was expecting this would be an unbelievable shift in my view of the universe.
Unfortunately I will not be here. I am laying in my new temporary hospital bed here at home, as cancer eats away at my body, with probably only a week or two to live.
—————————-
Ethan, your explanations of the workings of the universe have been absolutely delightful. I cannot say how much this website has meant to me. Really!I also want to thank you for the kind sentiments you expressed to me in the past when I was enduring totally unnecessary legal troubles. It was genuinely an uplift to receive your understanding comments."
My usual approach here is useless. I am happy I've been able to add a little bit of joy and wonder into your life, but sad that your journey is coming to an end. If you've got perhaps a few weeks left, feel free to privately (at startswithabang at gmail dot com, the same place Ask Ethan submissions go) send me the address of where you'll be and I'll send you a little something. If you want to speculate as to what the next great breakthroughs of James Webb (or WFIRST, in the 2020s) might bring, here was the best I could come up with.
The near and far sides of the Moon, as reconstructed with imagery from NASA's Clementine mission. Image credit: NASA / Clementine Mission / Lunar & Planetary Institute / USRA.
From Nerd on destroying the Moon: "Hmmm…. what could possibly destroy our moon?"
An asteroid made of antimatter. A large enough (e.g., moon-sized) impactor. The death star. Princess Celestia. Or, as Michael Kelsey suggested, Chairface Chippendale.
You never know.
A large collection of many thousands of galaxies makes up our nearby neighborhood within 100,000,000 light years. It's dominated by the Virgo Cluster, but many other mass collections abound. Image credit: Wikimedia Commons user Andrew Z. Colvin.
And finally, from Gab on the idea of a cosmic supercluster: "When I think of cluster I think something bunched together, I think some parts might move away, but generally its a clump or cluster. It still exists/ed."
You know, before dark energy, it made a lot of sense to call these huge collections of galaxies in space "superclusters." We said that we, ourselves, lived on the outskirts of the Virgo Cluster. Why? Because, in a decelerating Universe with overdensities of the magnitude these objects have, we would someday see ourselves fall into Virgo, and wind up bound together with the rest of the Virgo Cluster galaxies. We'd also see these clusters merge together -- often along the dark matter filaments -- into a true, bound supercluster.
Dark energy now means that we are not a part of Virgo; we are part of our local group and that will remain forever isolated from not only Virgo, but from all the nearby groups like the Leo group, the M81 group and even the Maffei group. But it also means that of all the "superclusters" we've drawn circles around, none of them are real structures. All of them will wind up forever unbound. That's why there's no such thing. At least, not according to a reasonable definition of structure.
Thanks for a great past week, and looking forward so very much to the coming one!
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I can't get an answer to a simple question: Does special relativity actually claim that distance, between stars for instance, depends on the speed of a traveler between them... not just "apparent" distance, but actual astronomical distance? (See my comments on the article about the variable orbit of Earth, depending on the speed of the "Trekker. No answer.)
I can’t get an answer to a simple question: Does special relativity actually claim that distance, between stars for instance, depends on the speed of a traveler between them… not just “apparent” distance, but actual astronomical distance?
In SR, reality will look different to different observers. To someone observing the starship from the outside (watching it fly by), the astronomical distances between stars and things will not appear to change. The starship will appear to foreshorten/contract along it's travel axis and the people in it will move very slowly due to time dilation. But to people *on* the starship, the starship is normal, time is flowing normally, and it's the stuff outside that appears to have changed.
"I can’t get an answer to a simple question:"
The question is quite meaningless. The distance is whatever you measure and how you measure it.
All that SR means is that if two people start off at the same point and both measure the time and their speed to get the distance travelled to the end point, the one who went faster will measure a shorter distance travelled than the other.
Space is expanding too, and what was where you thought it was has moved on by the time you get there, so what distance you measure depends on your trajectory and where you tracked the end point to.
And then there's the proper motion. So if you were to travel at Voyager speeds to Andromeda, the distance would be a lot less than the 2Mly because it's travelling in our direction.
Ethan are you going to do anything about that fucking annoying retard shithead john? Or is the upping of the money for your site worth more than the ability to actually reach people?
What are you here for? Cash or to educate?
Wait, wait...you, Wow are complaining that Ethan may be allowing someone else to post excessively just for the clicks?
How many posts did you make on this board in Feb? And most of them basically just replies to John.
Yes, eric, I'm complaining. Got a problem with your eyesight, you fucking idiot?
I take it you posted #5 to increase the clicks, yes? Because apparently to you, posting what isn't needed is what you think is shitposting for clickbaits.
Or maybe you need to get a frigging clue and stop being such a priggish twat and get out of your fucking bed and do something useful for once in your pitiful life.
Now fuck off.
Ethan it looks like it's clearly what you want to have that shithead john lying about what you said and shitposting bullshit and lies because you prefer to get paid far far more than anyone get educated, and that even if the education aspect is fucked beyond all repair, you will just accept the cash anyway.
You can fucking defend yourself and your site then you lazy asshole, I'll be only posting to lulz the trolls and not even care that bullshit gets posted and not give one tiny shit myself if I'm going overboard, because you clearly do not give one singly tiny miniscule of a fuck if this site goes to shit.
Well done, retard, you've just let this site turn into the shitpool that Deltoid became when Tim stopped caring about the site and did fuck all.
And still John "teabaggie" keyes 1000 shitposts repeats his lies because he knows nobody cares about lies, especially not Ethan, who really only wants to get views. Fuck whether any actual real information and learning is buried under bullshit.
About the only learning moment is how fucking batshit crazy the "moderate" christians like him are and how little difference there is in their insanities than it is for the "vilified" extremists.
But the only ones who would benefit from seeing that are not the sort who would want to learn from it, and so it's a fucking waste.
I hope you put some actual effort into your day job, Ethan.
6.0 for the flounce. 9.0 for the quality of the threat not to post much any more, but I'm forced to deduct three points because you'll never stick the landing.
Eric, I do not challenge that, as you said, "In SR, reality will look different to different observers." I challenge the SR dictum that length contraction is not just an "apparent " contraction but an actual shortening of lengths of objects and distances between them. Traveling at high speed between stars (or around the sun, as in Ethan's recent article) would not, obviously shorten the actual astronomical distance between stars... or Earth's orbit around the Sun. Clearly if the orbit were "really" shortened, the radius would also shrink and Earth would fry. And the distances between stars would not vary with all possible speeds and directions of "star trekkers." Ps: The nasty tone of comments here degrades the scientific credibility of this site, which allows them.
What fucking flounce you assclown?
Find somewhere from your arse a small nugget of reality and chew on that for a while, retard.
Yeah, the tone argument doesn't mean shit here. John teabaggie Keyes has dropped to spam the fuck out of a second thread and now given up doing any more than posting the same three posts again and again, even lying about what Ethan says to "support" his nonexistent case, and Ethan doesn't give a flying fuck.
So, yeah, if you don't want rude words, fuck off somewhere else. If you want to learn, ignore the tone and look at the content. But if you're going to piss and moan at the tome and ignore learning, well that's your frigging choice, not anyone else's fault. Take responsiblitiy for your own actions, you snowflake, and learn to live this life instead of demanding that you get everything served to you on a platter as you like it.
In that example the "observers" of importance are the Earth and the Sun. And yes they in fact do experience relativistic effects in relation to each other. You could calculate the time dilation experienced by observers on Earth in comparison to some observer on the 'surface of the Sun' due to our orbital motion - there will be some, and at least in theory this will affect the Earth's orbital mechanics. Though I bet the opposite GR relativistic effect would be larger, so that the net effect is that an observer 'on the surface of the Sun' would age slower.
In any event, the reason a suddenly accelerating starship wouldn't cause the Earth to dive into the Sun or cause Alpha Centauri to suddenly loom large in our Earth-bound telescopes is because the starship doesn't impact how the Earth moves in the Sun's frame of reference, or how either moves in Alpha Centauri's frame of reference (or vice versa). When the starship accelerates to near-c, these objects do not suddenly change v or a in each other's frame of reference. So they experience no new relativistic effects in relation to each other. The suddenly accelerating starship would experience relativistic effects between itself and Earth, between itself and Alpha Centauri, because its v and a have changed in their frame of reference (and vice versa).
@Ethan wrote:
There are kernels of truth in most of it. I’m swapping right side #3 with #4 just because I think it lines up with the left counters better.
This one is easy. It is not the Apocalypse. I have not read a single credible projection showing that a rise in temperatures or sea level threatens to wipe out humanity.
Both are true. We both agree on Scientists as Friends so I won’t waste time on it. The term ‘Cultish Cabal’ is used here as a pejorative. The more scientifically correct term would be ‘Cohesive Moral Community’ and academic scientists absolutely qualify.
Currently self-identified Democrats outnumber Republicans in American society by 1.06:1[Gallup 2010]. In academia the number is roughly 14:1. It was only 4:1 as recently as 1990 so the problem is quickly getting worse.
http://heterodoxacademy.org/wp-content/uploads/2015/09/diversity-graph…
Research has shown that viewpoint diversity has a larger positive effect on the quality of research efforts than does ethnicity, race, or gender diversity (Menz, 2012; Williams & O’Reilly, 1998). Despite demonstrable quality advantages, research academics are going in the opposite direction.
From Inbar and Lammers (2012):
From Inbar and Lammers (2012):
The hostility is not limited to just workplace climate or gaining employment. There is published research showing viewpoint biases in receiving grants and getting published. Academic Scientists are now a Cohesive Moral Community that has been screaming that they want nothing to do with moderate or conservative America. It shouldn’t be a surprise if the feeling is becoming mutual.
It seems that both sides agree on this one.
Per the description on the left:
Per the description on the right (quoting Rick Santorum)
Is the climate getting warmer? Yup. Are there people of the left trying to leverage it for political gain? Yup.
Although I love a good conspiracy theory I’m not sure there is much of one here. There may have been money put towards marketing efforts to dispute the warming climate narrative, but that is politics not conspiracy and all sides engage in it. There are definitely those on the political left who have pushed talking points to ridiculous extremes.
Al Gore made a lot of money. James Hansen made a lot of money but not nearly as much as Al Gore. California Governor Jerry Brown just spends boatloads of my money on his stupid multi-billion dollar bullet train. The world would have been just fine if none of them entered public life but you can count on there being more individuals endeavoring to leverage the situation to trying to make money, gain fame, or grab political power. It is not much of a conspiracy, just people working in their own best interests.
Nah, looks like standard rightwing nutjob conspiracy talk, manufactured to let them pretend that it doesn't matter how much of a fuckup they are, "the other side" are far worse, therefore your own craptaculence is not merely acceptable but the "moral choice".
Basically, the rightwinger projection.
Try visiting reality on the subject. You managed it where your politics don't get involved, it's only when your libertarian ideals are shown up to be a failure and immoral that you get all ballistic and ignorant.
This is selective use of data if I've ever seen it. "Academics" are not the same groups as "scientists." A much much better data set to use would be the PEW 2009 survey of AAAS scientists. The result there was 6% registered Republicans, 55% registered Democrats, 32% independent,and 4% other. Which is still a liberal skew, but far far more diverse and more centrist than your claimed 14:1. When you ask the independents which way they 'lean,' it gets even more reasonable: 82% lean left to 12% leaning right. That's less than 7:1. so the actual breakdown is much closer to the 1990s ratio you used than your putatitve 14:1. Also keep in mind that when PEW asked the general public the same 'lean' question, it was 52% left vs. 25% right, so a 2:1 skew left is the baseline to which we should be comparing, not 1:1.
Exactly what political gain do you think I get from carbon taxes? From higher energy prices? Do you think the people who accept the mainstream position on climate change are sitting around going "ooooh, I can' wait until my power bill goes up! That will show those deniers! Muhahahaha!" That's absurd. There is no overall or general economic gain in having to address the damage humans have done to the environment. It's pretty much just costs. Bills the human race has to pay for being short-sighted in the past. The tragedy of the commons. I would love not to pay these costs. However, part of being a grown up is accepting when the data tells you something unpleasant, that's going to cost you and that you'd rather wasn't true.
In terms of party politics, I'd much rather have both parties accept that climate change is occurring, a problem worth addressing and discuss what to do about it, than have Dems win youth and science votes because they're the only major party who thinks it's an issue. And I think my position on that is pretty standard for any non-denier - after all, the former is pretty much the political situation in the rest of the first world, and AFAIK most people who accept climate change here in the US consider that a good thing. We want both parties to work on the problem. And frankly, any dem who thinks "oh good, the GOP is denying climate change..well, we'll get a couple more representatives out of that" is an idiot who is putting tribal loyalties ahead of the good of the country.
@eric wrote:
That comes out to a 9.2:1 ratio in 2009. The source I cited showed the ratio to be ~11.5:1. Those numbers are in the same ballpark. The 14:1 ratio is simply newer data. A quick glance at the internals show there is even more bias in the pipeline.
http://c1.nrostatic.com/sites/default/files/Democrat-to-Republican-rati…
Professors under the age of 36 have a 22.7:1 Democrat to Republican ratio. What few Republicans there are seem to be older. As they retire the Democrat to Republican ratio will continue to slide ever more in the favor of Democrats.
I'm not even sure what you are arguing. Even in your out of date numbers where you squint to add in independents, there is still a ridiculous viewpoint bias. It is bad. It is getting worse. Hostile work environments and prejudiced hiring practices clearly demonstrate that it isn't accidental.
"Exactly what political gain do you think I get from carbon taxes?"
He neither knows nor cares, all he wants is to give you a BAD reason for your claims, therefore your assertions and evidence are only fake evidence to support your bad intent.
After all, this is how the rightwing roll, they can't conceive of anyone doing anything different.
When you see denier give you a bad intent, it is always 100% projection.
Denier, the reason why democrat academics so outnumber republicans is because of two reasons
1) Democrat and progressive policies are just the sane and rational choice for anyone who thinks about more than themselves, and academics got into the job to teach others.
2) Republican policies are dumbass and short sighted, so the more intelligent you are, the less likely you are to accept them.
3) Republicans hate academia so choke it and reduce the pay, so they're hardly going to go into that job, are they.
4) Repunlicans, thinking only of themselves and their "winning" in life go for the high paying jobs where ethics and morality do not matter, meaning that politics and big business (and lawyers) are their go-to professions.
Basically if you're an academia you're smart enough to work out how abhorrently stupid republican politics is, and the pay is so tiny as to make republicans, who only count wealth for themselves, avoid academia.
Want more academics being Republican? Tell your pals to take the jobs. Currently they no more want that job than women want to work down coal mines.
PS didn't you pretend to have a missus who was a scientist? Unless she's a democrat too, it looks like the academics aren't trying to force their political opinions on their students, so what exactly is your whinge about?
Eric, You have not addressed my challenge. SR claims that there is no objective world independent of all possible different frames of reference, i.e., that length contraction is not just "apparent" (as Ethan confirmed in the "trekker" article) but actual, because "all frames are equally valid" and "length (or distance) is not invariable" (It actually varies.)... so the distances between stars (etc.) depends on the speed and measurements of the trekker. No "real" world... it all depends on how we look at it. Address that if you will. ( I'll be unsubscribing from this trash talk site soon.)
Well you HAVE been answered but it appears you just insist it's not answered by making it a different demand.
How dumb.
There is a defined distance between two objects in meters or whatever linear dimension you choose for your unit, but that only applies to something in an inertial frame "at rest" between the two, and both of those are also "at rest" with each other.
Stand still and measure the length of a table and as long as you and the table are stationary together, that table will measure its "real" size. Someone NOT stationary with respect to the table measures a different length of the table.
You changed you demand.
And therefore THAT is why you never get your demand answered: you don't want it answered.
And that's why your dumb ass deserves the trash talk.
I note too that you are a SERIOUSLY fragile little snowflake sine you've not been trashed talked by me but you've merely witnessed it happen to others. Yet STILL you are massively butthurt, so that you can't help but pre-emptively whine about it. Well you can keep your whining ass safe in the internet by shutting the fuck up and staying in your safe little cave.
Note you don't subscribe to this channel, dumbass.
Michael Mooney,
"... I’ll be unsubscribing from this trash talk site soon ..."
Just ignore the background noise. There's very little information content there.
Yeah, but you're the retard who keeps lying about what people have said and then, as opposed to finding an actual argument, repeats the same posts.
So, really, it's all just a reaction to your idiocy that's going on.
YOUR FAULT, teabaggie. And oh so easy to fix: buy a gun, blow a hole in your head! It'll let the ideas in, then! Be open headed!
Michael Mooney,
Res ipsa loquitur.
"Hostile work environments and prejudiced hiring practices clearly demonstrate that it isn’t accidental."
You have no more clue about academic life than you do science.
Or he's giving us the admission that he's trolling, badly, because his shit hasn't been believable for a few months now and recently descended into just spam posting the same three debunked arguments to avoid being wrong on the internet.
I.e. his idiocy has not been accidental.
'course it's really not clear that we have an actual person in Mooney here, since he came along, said he'd never been answered a question, was answered at least three ways quite accurately, then complained it was not answered, all the while whining about tone.
A coherent picture arises if you take the question mooney posted as a vehicle to complain about tone rather than an actual request.
Meanwhile teabaggie, having not had to repeat his lies because they're currently the last word on the killer thread and he takes that, like any three year old would, as having won, is pretending on any thread anyone would visit without cancelling thinking the site broken that he's not a sick mad individual with a massive problem they can't handle. Perfectly matching the abusive personality disorder.
Yes I did. You asked if SR means the distance between objects is contracting when some relativistic spaceship travels between them. I said very clearly that to you on Earth, it doesn't.
This is a different challenge, not what you asked before. AFAIK in SR the passage of time is dependent on reference frame, yes. I have honestly never heard anyone talk about length contraction of the space traveled; in SR, "length contraction" almost always refers to how an object traveling at relativistic speeds in comparison to an observer will look to that observer - it is not used to refer to how the space between stars will look to that observer.
The first sentence may be true (I hedge simply because this is not my area of expertise). The second is your philosophical interpretation of what it means. Relativity is the theory most consistent with observation. It's highly accurate. Not liking what you think are the implications is not a valid criticism of it.
Or to put all that more simply: you appear to be just asserting the 'personal incredulity' fallacy. The theory of relativity appears to be accurate. If you don't like the implications, well, the universe doesn't owe you rules and laws that are intellectually satisfying to you.
Eric, You said, " I have honestly never heard anyone talk about length contraction of the space traveled." You will see it in any science forum with a relativity section, "Ask a Physicist" (about the contracted distance to the nearest star at near light speed) and from Ask Ethan's piece about trekking around Earth's orbit at high speed, as follows:
" The faster you move... the more space **appears to be contracting** in your direction-of-motion. ... If time runs at a different rate, then space needs to **appear** a different length for everything to match up." (My **emphasis.) My comments on that piece complimented him on using the word "appears" rather than insisting on an actual physical contraction of distance traveled. Finally, you said: "You asked if SR means the distance between objects is contracting when some relativistic spaceship travels between them. I said very clearly that to you on Earth, it doesn’t." My point is and always has been that differences in *apparent length* "to you on Earth," for instance, do not indicate differences in actual length, "in the real world" as per changing distances between stars with all possible different speeds of theoretical trekkers. That is as clear as I can be about my challenge... which Ethan still refuses to address. I'll wait for your reply before I unsubscribe. Thanks.
Well I guess the best way to answer is to say:
1. If by 'real world', you mean some preferred frame of reference, then there isn't one in SR.
2. If by 'real world' you mean the frame of reference of you and me here on Earth, then for the third time: no, the space between stars doesn't contract as we observe a relativistic starship moving from the Earth to some distant star system.
I suspect you have a philosophical problem with #1. You either don't see how it can be true or don't want to accept that this is true. I can't really help you with those problems, except to say that relativity is more accurate than any other theory that posits a preferred frame of reference, and that when one's intuition of how the world ought to work collides with facts that seem to demonstrate your intuition is wrong, I would recommend giving up the intuition rather than the facts.
Eric, " If by ‘real world’, you mean some preferred frame of reference, then there isn’t one in SR." "In SR." I understand. In fact, the cosmos is at least 13.8 billion years old, if not eternally oscillating, so "it" (the "real cosmos") exists independent of all "observation and measurement" from different points of view ("frames of reference.") I speak for objectivity in science. Relativity is based on the basic philosophy that It all depends on how you look at it ... from different speeds." Again, "no real world independent of observation."
That's just babbling now, mooney.
Reality is what you objectively see, therefore you#re making a problem out of something you've made up yourself. No wonder you've never had an answer: you don't even know what a question is.
This is a fairly common error. When scientists speak of 'observers' in relativity or QM, they just mean anything interacting with the subject. Photons are observers. Particles are observers. So the universe does and can exist independent of people observing and measuring it under relativity. If that's what you're worried about.
The effects of relativity are objective; they can be measured independent of individual human perspective. Mercury will continue to precess regardless of whether we are looking at it or not and we know this, because it developed a stable orbit long before humans existed. The light from distant stars is a view back in the past long before humans existed. And so on.
Moreover, as I said before, the fact that you "speak for objectivity in science" doesn't mean the world is objective in whatever wierd way you mean. Again, the math works and is accurate regardless of whether you accept it or not, whether you think it makes sense or not. The universe did not promise you an 'objectivity' that you agree with.
@ Michael Mooney
"Does special relativity actually claim that distance, between stars for instance, depends on the speed of a traveler between them… not just “apparent” distance, but actual astronomical distance?"
Like eric and other pointed. No, SR doesn't claim anything of sorts. It might have been a good idea to show/link why you think so in the first place, but SR doesn't claim what you think it claims. What SR showed is that Lorentz coordinate transformations are real, for space and for time. In fact, they transform in union, thus spacetime. And if speed of light is same for all, then spacetime has to change depending on the speed of observer.
If you label stars A and B, and observers o1 and o2. SR doesn't say that the distance between starts A and B changes for o1 (who is maybe on one of the stars... or on some star C i.e.) IF o2 is moving anywhere. What it does say, is that thing will change for o2 IN REFERENCE to o1 depending on his speed. It says that all measurements are relative to the reference frame from which they are measured. Or in other words...you can claim "reality" only from local reference frame, you can calculate "reality" for other reference frames. But those two are not the same.
To end with your two stars. There is no absolute distance between stars A and B. There is distance from A to B from reference frame A, there is distance from reference frame B to A.. (they are same only if A and B are in rest with one another)... and then there is distance from A to B for someone looking from C... and from D which is much further then C... Depending on relative speeds between all of these actors... every distance or time measurement will be different for every one of them.. or same.. but the point is that it can and doeschange.. it's not absolute like in newtonian dynamics, but depends on motion.
p.s. one problem with your question is that you say... "apparent distance" and "astronomical distance". I don't know what you mean by those two, since they are not standard measures. What is apparent distance between A and B? Distance between A and B for me here on earth? Or distance between A and B for someone in a spaceship going to B? Or distance from A to B for someone on A? See what I mean?
Same for astronomical distance. For more about different distance measurements in cosmology, try
https://en.wikipedia.org/wiki/Distance_measures_(cosmology)
The "speed of the observer" is with respect to the emitter of the light whose speed you are measuring. Just clarifying that for you, SL. IMO this may be where a lot of morons and just uninformed (the former being wantonly the latter, the latter on its own is the default state for all humans until you find out) get the idea that there's some "absolute frame of reference", because the "speed of the observer" is nil compared to the speed of the observer, so it can appear like the speed here must be relative to something else and since it's never defined when this phrase comes out, presume it to be some absolute still point.
It doesn't, it's speed relative to the speed of the light emitter you're measuring the speed of the light that came from
The “speed of the observer” is with respect to the emitter of the light whose speed you are measuring.
Yes.
@Michael Mooney,
I suspect your problem with relativity is that its effects don't really manifest themselves in everyday situations. Very likely, there has never been a situation where length contraction has been observable for you, for instance.
That means that relativity's effects can seem to contradict common sense. That's okay, though; common sense is nothing more than the knowledge acquired by your own experiences. Science can and does go beyond common sense. Contradicting common sense does not indicate that a scientific idea is untrue.
To really understand relativity, you must give up ideas of common sense. One of these is absolute motion. We talk about objects as either stationary or moving. There really is no such distinction in reality, though. Consider, for instance my velocity as I sit in my chair typing this. What is my velocity? With respect to my chair (and the floor of the room, the surface of the earth, etc.) my velocity is indeed zero; you would say I am stationary. With respect to the center of the earth or the north pole, though, I am moving at a quite high velocity in a circular path. With respect to the sun, I am moving in an elliptical path with an even higher velocity. With respect to the center of the galaxy, I am moving even more rapidly.
Which of these, then is my real velocity? Am I stationary or am I moving? I hope you can see that these questions really don't make any sense as they stand. ALL of these velocities are equally real; they simply represent my velocity in different reference frames. This idea that velocity is not absolute, but relative to a reference frame PREDATES relativity. It is part of classical mechanics. It is possible to grasp this from common everyday experience, such as the ones Galileo outlined in some of his writings.
Relativity merely extended this idea to distances and times. The distance between two points depends on the state of motion of the observer who is measuring it. The time between two events likewise depends on reference frame. Does this mean that NOTHING is absolute? Relativity answers this with a resounding no. Objectivity is alive and well; it just doesn't have the form you think it does. Distances and times are not objective in that sense. Only something called a spacetime interval turns out to have an observer-independent value. The subject of discussion in relativity is events. We can specify an event by recording three spatial and one time coordinate - ie. when and where the event occurs. A spacetime interval then is simply the difference between two events. It is given by:
s^2 = c^2(t1-t2)^2 - (r1-r2)^2. This is the objectivity in relativity; ALL observers looking at two events will get the same value for this expression. They will not all agree on the distance or the time between the two events.
If you really think carefully about this, this is as it should be. Relativity is nothing more than the idea that all observers are equally valid. There is nothing special about a person who is stationary with respect to the earth's surface. The laws of physics should not apply differently to people on earth, people travelling in fast spaceships, or anyone else. The implications of this simple idea are counterintuitive, to be sure, but that's simply because there has never been anyone who has directly experienced anything close to a relativistic situation.
Eric (and all), I understand that a frame of reference does not require a personal observer. Yet, for instance, any frame of reference approaching Earth at 86% of light speed will "see" Earth as flattened to half its *actual* diameter in the direction of the approach. Clearly that would be only "apparent," to use Ethan's word, as I quoted above. Likewise the actual distance between stars does not vary with the frame of reference from which they might be "observed"
As I replied before I *do not challenge* that, as you said, “In SR, reality will look different to different observers.” I challenge the SR dictum that length contraction is not just an “apparent ” contraction but an actual shortening of lengths of objects and distances between them.
Again, Ethan said, "If time runs at a different rate, then space needs to **appear** a different length for everything to match up.” (My **emphasis.) My comments on that piece complimented him on using the word “appears” rather than insisting on an* actual physical contraction of distance traveled.*
Either there is an "objective world" independent of how one (anything) looks at it (objective realism) or "It all depends on how one looks at it (subjective idealism,... subject being any theoretical point of view.) SR insists on the latter as The Truth. Yet Earth remains nearly spherical regardless of how it might **appear** from various relativistic frames of reference. Do you at least agree with the last statement? It sums up the debate here for my part. Btw, thanks for the serious answers.
I think you may be missing the point, however, that the calculations of motion, orbits, momentum, etc. done in each reference frame will be consistent with each other once the correct frame of reference translation is done between them. It's not like one person will say "based on it's measured speed, size, and orbital parameters, I calculate the Earth should fall into the Sun" and a person in a different frame of reference will get "based on speed, size, and orbital parameters, I calculate it won't." They'll both get exactly the same answer. That's because the relativistic traveler will also have a frame-of-reference different view of the Sun's size and motion and the Earth's speed and orbital parameters - not just a sole difference in the Earth's apparent size. And all those differences will add up to the exact same prediction that his friend sitting on Earth would make. So there aren't 'different realities' here; there is one. Viewed from different perspectives.
I'm not sure what shape it would appear to an oncoming relativistic traveler. However let's say it appears to them flattened like a face-on coin. In that case, if that traveler wanted to make a correct mathematical prediction as to the Earth's movement around the sun, or make a correct prediction about how to establish a stable orbit around the Earth when he get's there, he would have to use a 'flattened coin' geometry of the Earth - consistent with what he observes out his window - to get the correct answer. If he treated the Earth as a sphere in his frame of reference, he would get all the wrong answers. So for him, the Earth is not best approximated as a sphere. Heck, even if you asked him to calculate "the shortest path from London to Beijing", he would do that most accurately using the flattened coin geometry. But then, when you took his answer and converted it into an arc in our frame of reference, you would get the correct arc to use on a spherical Earth.
So again: one reality, different frames of reference used to describe it.
Eric, Regarding your statement, " I’m not sure what shape it would appear to an oncoming relativistic traveler." I am sure that at .86 c, Earth would *appear* flattened to half its factual diameter. Earth's nearly spherical shape does not change with every passing "observer" at whatever speed, in whatever direction. The math works just fine to translate 'appearance' into actual physical reality. Most planets and stars remain close to spherical, because the laws of physics are the same everywhere. Point of view does not change the physical cosmos. Sorry, but that is merely "common sense," now debunked by relativity theorists. ... so you all insist. Last call to show me how Earth changes shape to accommodate all passing high speed points of view. (Kidding but also serious, if you know what i mean.)
@ Michael
I think I understand your objection, but have to say... it's a personal objection.. doesn't change reality :)
You say " any frame of reference approaching Earth at 86% of light speed will “see” Earth as flattened to half its *actual* diameter in the direction of the approach....Yet Earth remains nearly spherical regardless of how it might **appear** from various relativistic frames of reference."
I guess, at the end you are asking.. "so which one is it?" Which one is real? The answer according to SR is they are both equally real. Not in some QM sense of multiple universes... but in a sense.. that to you.. who is stationary in reference to the earth.. it does appear as a sphere.. and every measurement you make will tell you it's a sphere. That's your objective reality.. or apparent reality as you say. But to someone moving at 85% of c in reference to earth and you.. it just ain't so. Like you correctly said.. to him the earth looks flattened. But not only "looks" or "appears" like it's some kind of illusion. This is maybe what confuses you. The correct wording should be.. To him/her earth is not a sphere. Any experiment he does will give him an answer that earth is in fact a pancake. In his reality bodies that are spherical are elongated in our reality. Earth is not a sphere to him, but some asteroid that doesn't look spherical to us, is spherical to him moving at 85%c in reference to it. We say it "appears different".. because to us, reality is being in relative rest with our surroundings.. but the fact is .. it really is different and is relative to your motion.
p.s. like eric mentioned.... physics stay the same.. it's just the geometry that changes. So reality is that you can say.. this ball is made of rubber.. and it will bounce.. but that it's a ball and round is true only if you are at rest in reference to it.
At the risk of introducing an excessively simple analogy, Michael, you might think of relativistic frame of reference transformations as somewhat analogous to unit transformations. If I say I am 150 lb. and you say I am 68.25kg, there aren't "two realities" to my weight. There's just one reality of my weight, measured in two different ways. If you know the lb.-to-kg mathematical transformation, you can switch between one and the other. The theory of relativity came with (well, I believe a bit afterwards) a set of mathematical transformations that allow us to do the same thing between relativistic and non-relativistic frames of reference. When you do the transformation right, you find that all frames of reference yield functionally equivalent answers for questions like "what path do I chart", "will the Earth fall into the Sun today", or "how much does eric weigh." I am glossing over so much that no doubt some several of the regular contributors are probably facepalming right now, but for a beginner at this stuff, I think that may be a helpful analogy for approaching the subject.
Here is something that gives a real world example and might give insight into length contraction
https://en.wikipedia.org/wiki/Muon#Muon_sources
one thing i want to edit about pancake earth.. is that since the transformation applies only to the coordinate of movement, our would be 85%c traveler would never observer the "coin" side (or would observe it only if passing by earth and moving on), but if he wanted to actually view the coin side.. he would slow down and get a sphere again.. or even if he did a 90% manouver at 85%c .. he would still get the face again...even tough he saw it as pancake while he was approaching. So yeah... geometry is funny that way :)
Thing is, going at 85% the speed of light, to measure the distance you have to at least shine a light and see it reflected back from the nearest surface, and then it has to travel back. By which time you've moved a LOT closer, and the reading you got is incorrect.
Just like if I ask you for the precise time. By the time I've heard it, it's no longer that time and it's imprecise.
And if you're looking at a spherical earth, then you'd have to be going past it, not toward it, and then you're not seeing lorentz contraction. No matter how your metric has changed, you will only see a disk face on and "perfectly" round. Not elliptical at all.
Mooney, your "problem", if it were actually genuine, was mixing up two different frames of reference and trying to make them both agree, when they don't have the same frame of reference and they do not have to agree on some third party or obejct.
Travel to earth and in the dimension you can't see, it's not the same axis, but since you can't see or even measure it, it's rather moot to call it different, isn't it.
Dr. Einstein, why did the chicken cross the road?
"Whether the chicken crossed the road or the road crossed the chicken depends on your frame of reference."
Just a quick reply to your condescension, Eric: (I'm busy): "... but for a beginner at this stuff, I think that may be a helpful analogy for approaching the subject." FYI, I have been an avid student of relativity for over 50 years. I'm 71 and started young.
Try to understand the error in the philosophical basis of SR,... that, as Einstein insisted, (paraphrased) 'It all depends on how you look at it.' So then there is no world existing independent of "observation" from whatever .perspective. End of this reality check.
You clearly haven't been avidly studying it for comprehension then. Three years of avid study is more that sufficient, even time spent as a hobby doing it.
And you don't get to claim "the error in the philosophical basis of SR" based on your half-assed and entirely personal definition of the theory.
"“Whether the chicken crossed the road or the road crossed the chicken depends on your frame of reference.”"
Actually, this is why the entire thing is relative.
If the chicken was travelling at a large fraction of the speed of light, you would not see the chicken cross the road at the same time as the lorry passed before it safely, since the sight of the chicken's arrival at the road arrives to you BEFORE the lorry's reflected light reaches you, therefore you "see" the chicken cross the road before (if it were travelling toward you) it really did.
Time dilation really is nothing more than the realisation of the invariable law of cause and effect.
...then...
Change 'observation' to 'frame of reference', and I think you've got it. Any time you calculate an interaction between objects, you must describe them in a common frame of reference in order to get an accurate prediction of how they will behave.
The math of SR may be difficult in some ways, but conceptually this idea is not. if I describe a parabola as y=x^2 and a circle as r(phi) = 1 and I want to know where they cross, I must first choose either the polar or cartesian system in which to work the problem. Then I must translate one of those equations into the form appropriate for the system I chose. Then I solve the problem. If, instead, I try to combine a polar coordinate equation with a cartesian coordinate equation without first using the right transformation between them, I'll get gobbledigook.
Eric and Sinisa, first, thank you for your time and sincere attempts to "explain" length contraction to me. Yet I have studied SR arguments for most of my life. My constant appeal is to clearly distinguish between how things *appear* differently contracted from different moving frames of reference (as per relativity) and the actual physical shape/length of things prior to (independent of) any observation/measurement. I hope we can agree (with astronomy) that stars and planets are physically nearly spherical, due to the *laws of physics* acting upon them during their formation. (Yes?) So if a theoretical near-light-speed traveler (or nominal point of view) "sees" Earth as flattened ("pancaked") in the direction of approach, he must apply the Lorentz formula to correct for the *distortion* and deal with it as the near sphere it actually IS, for whatever purpose... say to slow down and orbit, at which time its *proper diameter* and shape as a sphere will come into focus. But Sinisa insists, "It really is different (ed: flattened, in the example) and is relative to your motion.... to him/her earth is not a sphere." "To him/her" insists that there is no objective physical stable body, Earth independent of whoever/whatever approaches at whatever speed, from whatever direction. I understand that it will *appear flattened" in the direction of the approach and to a degree of contraction depending on the speed of approach. (Half its proper diameter at about 86 c.) It is my impression from Ethan's use of the word "appears* as cited above, that he agrees with the above. I hope he will either confirm or deny and explain his position on *apparent contraction. "If a tree falls in the forest and no one is there to hear it, does it make a sound?" (Classical idealism says no. Objective realism says yes.) Yes, there is a "real world" independent of observation or point of view.
@ Michael
I think that we all agree on what SR says and what occurs. The only difference is that you seem to infer that we ought to really consider things at rest as default state of being. All I'm saying is that "default" isn't a default. The only way I can explain is... consider a scenario where an observer CAN'T (for whatever reason) alter his frame of reference.. i.e. like a muon... or our 85%c observer. Let's discuss a scenario where he can't slow down... or accelerate more.. His whole life he's moving at 85%c in relation to planets/stars in our galaxy. What's reality for him? You say.. " he must apply the Lorentz formula to correct for the *distortion*"... I say no to this. He doesn't have to do anything... nor would Lorentz tranformation do anything for him. Only thing they will do is show him i.e. what someone not moving as fast as he would see. But that won't change how he experiences the universe. So there's no point for him to calculate anything since he can't slow down. What you consider distorted, he considers normal, what you consider normal, he considers distorted. And that's it. It's like looking at the world through lenses... you think he is wearing lenses... and he thinks you are wearing lenses. But I don't see a point of going with ... it's the one who sees contraction that's actually wearing lenses.. and what we see is the real state of things.
as for realism.. don't think the old tree example applies here. This isn't a philosophical issue like which interpretation of QM to go with. When you compare two clocks in the lab after one has been in orbit.... there's no going back from that. No transformation of coordinates will make the clock come back in sync with the stationary one. Those two clocks are in different time "realities" forever.. down to the subatomic parts. You can't say that the timeframe of first clock is more real or correct than of the second clock. And since time and space are correlated... IMO same applies for geometry.
I am still hoping that Ethan will clarify his position, in the article cited, on his use of "appears." Sinisa, Considering your example of the traveler who can't slow down to orbit and measure the *proper length* of Earth's diameter (and observe that it IS a near sphere... Do you agree that **the laws of physics** operate on all forming physical bodies throughout the cosmos in the same way, tending to form stars and planets into near spherical shapes? If so, calling a flattened Earth an "equally valid" description is simply false. It IS a philosophical issue... whether a theory is based on "it all depends on how you look at it" or on the immense body of scientific knowledge which is astronomy and the gravitational physics of how stars and planets are formed. (Near spheres, not pancakes.)
Ps: We all know that clocks accelerated to higher speeds ( or exposed to different forces of gravity) "tick" more slowly the faster they go or in higher gravity fields) No doubt the same for the aging process in humans. Please reply to the physics argument for formation of spherical physical bodies in space.
yes, I agree that the laws of physics are the same in all reference frames.
" whether a theory is based on “it all depends on how you look at it”" am sorry that you feel SR says that. It doesn't. Not how you look at it. How you move through it.
The reason I mentioned clocks is because the treatment is same. Does it appear to be moving slower.. or is it moving slower? You are stuck on some beef with spheres and words "appear" for probably reasons known to you, so I'll leave it at that.
So you choose to ignore my last sentence/ request. The physics of star and planet formation makes them nearly spherical. I'm not " stuck on some beef." It makes a huge difference whether the claim is "appears flat" (from a moving frame i.e. a length contracted diameter or "IS flat." "To this observer it's flattened" means "appears flattened" not "is" physically flattened." Physics does not form flat stars or planets, so they can only *appear* flattened to a fast moving frame of reference. Maybe this is just too obvious for someone "thoroughly schooled" in SR to the point of ignoring how physical bodies are formed in space. This is mere common sense physics, disdained by the elite club of SR theorists, for whom there is no objective physical world independent of all varieties of frames of reference Nuff said.
"This is mere common sense physics, disdained by the elite club of SR theorists, for whom there is no objective physical world independent of all varieties of frames of reference Nuff said"
Why do I think your "objection" isn't based on physics (which you seem not to understand as well as you think you do) but on the mistaken idea that relativity and "relativism" are linked?
This again assumes a specific frame of reference, where bodies are at rest with respect to each other and there are no other forces operating on them. I expect you understand that the rotation of planets tends to flatten them at the poles, right? So you accept that the "natural' shape of a rotating planet isn't actually a sphere; its an ellipsoid shape that is in part dependent on parameters of rotational speed, mass, etc...
So why do you find it hard to understand that when relativistic effects change an objects mass in comparison to another object, as well as the way time flows around it, a sphere won't necessarily be the "natural" shape of it either? Consider relativistic effects analogs of pseudoforces if it helps you.
In some ways its a distinction without a difference. You could just as easily say that physics does not form spherical stars or planets, they only "appear" spherical in those frames of reference.where objects are moving comparatively slowly in relation to each other.
The point is, every calculation, every measurement, every interaction takes place within a frame of reference. Yours too. The one you're attached to is the one that is most accurate when objects aren't too heavy and aren't moving too fast in relation to each other - like the things around humans, on earth. Thus it's very convenient for us. But that doesn't make it philosophically special. As Sinisia says, you seem very insistent that we all take the frame of reference of things at rest to each other as a philosophical defualt. There is no mathematical or physical reason to do that.
However, I guess to try to be conciliatory, I would also say there is nothing stopping you personally from preferring it. To be honest, IMO most scientists do calculations in whichever frame of reference or using whatever coordinate system its easiest to solve their particular problem in, without regard to any question of philosophical priority. They just don't care about the philosophical 'priority of frames' question you seem very concerned about. If, however, you wanted to do every cosmological calculation in your preferred frame of reference and spend money on supercomputer time to do it, rather than use a more convenient frame of reference using your laptop, well, it's your money.
Odd thing about spherical planets is that they're spherical in their own rest frame. But in a different rest frame, they're not spherical. In a non euclidian space, they're again not spherical.
And you move toward that spherical planet at high speed and it will not appear spherical form your point of view, but that's because you're moving very very fast toward it, and definitely NOT in the planet's rest frame.
No problem there at all.
"The physics of star and planet formation makes them nearly spherical."
Please write out the full 4-d relativistic equations that show this claim to be true, mooney.
Because in the ones you should be using, they don't. They're only mostly spherical based on spherical symmetry of forces and space, and in a high velocity space reference, there is no spherical symmetry of forces.
This is (AIUI) a general property how we use reference frames, that we arbitrarily pick something to be considered 'at rest' and calculate everything else around it. This tends to be the object we're on, or the perspective we want to take. Thus when the object of interest is a planet, that planet will typically be calculated out to be (mostly) spherical, just like when the object of interest is the relativistic starship on which we are traveling, we'll typically calculate that starship's shape to be it's resting shape.
We could always do it the other way (i.e. calculate Earth's shape from the perspective of a relativistic starship we aren't on, or calculate our moving starship's shape from the perspective of someone on Earth), but AIUI that tends to be much more mathematically complicated if you're interested in the physical interactions between things on Earth or in your starship (respectively), so why bother?
Ethan addressed my objection to physical length contraction yesterday, confirming that the *appearance* of contraction at relativistic speeds does not mean actual physical contraction as per physical flattening of stars and planets. I commented, thanking him for the clarification and suggesting that he and his friends at Starts With A Bang "inform the SR theory community" of this dissent from mainstream SR. Today both his comments and mine are deleted. CENSORSHIP! No one challenges physical length contraction! B.S.!
Yet it is universally true that the gravitational physics of star and planet formation make them nearly spherical. The flattening effect is only *apparent* (as Ethan said in the article I've repeatedly sited), not an actual physical contraction of their diameters. Now he has withdrawn his comment or has been gagged, and my reply deleted. THIS IS NOT SCIENCE.
CENSORSHIP RULES. I quit.
Sorry about the above post. My mistake (No "delete" capability. Ethan's comment about my length contraction challenge was in "Comments of Week # 152, as follows:
" From Michael Mooney on traveling close to the speed of light: “Does special relativity actually claim that distance, between stars for instance, depends on the speed of a traveler between them… not just “apparent” distance, but actual astronomical distance?”
It depends on the distance and to whom. If you’re in the spacecraft and moving towards a star 4 light years away, but you’re doing it at 88% the speed of light, then yes: the star will be only 2 light years from you, and you will reach it in a little over two and a quarter years. That contraction is “real”. Now your spaceship, to an outside observer, will also appear contracted, as the ball in the above image appears. Is that contraction physically real? We don’t think so. Relativity is still challenging to wrap your head around, even more than 100 years after we’ve first discovered it." (End quote. So the distance between stars depends on the speed of the traveler (no objective cosmos independent of frame of reference), but spherical bodies in space don't flatten out (contract in diameter) depending on speed of the observing point of view. ("We don't think so" anyway.) So what is the difference here. Please explain. Also explain how stars become nearer to each other the faster the observer moves. Neat trick for massive stars in the "real cosmos."
"This is (AIUI) a general property how we use reference frames, that we arbitrarily pick something to be considered ‘at rest’ and calculate everything else around it. "
Well, it's the result of using a system that is spherically homogenous. But in a moving frame of reference, the system is no longer spherically homogenous: the axis of motion is distorted in SR, and gravity can also distort the system in GR.
"but spherical bodies in space don’t flatten out "
They don't from their own frame of reference, where they are stationary.
But from the frame of reference of someone else, they do.
Mooney, instead of getting pantie-wadded, try and work out how you, travelling at, say 99% of the speed of light (so the change is quite extreme" toward an earth-sized planet, right at the middle, therefore you don't see a change from a circular shape from your face-on view, measure the depth of that planet to work out how it is not a sphere?