Last week, we began talking about understanding the size of the Universe, and we continued this week with some information on distances and motion in the Universe. This brings us to my favorite application, which leads to the Hubble expansion:
Redshift. You see, whenever an atom or molecule emits light, it gives off that light at a very few particular wavelengths. For instance, if you have hydrogen, you'll always get light at wavelengths of 656 nanometers (red), 486 nm (cyan), 434 nm (indigo), 410 nm (violet), and 397 nm (on the border of violet/ultraviolet):
Now there are three things -- and only three things (unless you really want to get technical) -- that can happen to this light to change the wavelengths that you see. Let's go over what they are.
1. Gravitational Redshift. If you're deep in a gravitational field (like close to a black hole), you have to use up energy to climb out of it. For light of all types, energy and wavelength are very closely related to each other. Smaller wavelength = higher energy and larger wavelength = lower energy, so if you need to climb out of a strong gravitational field, you lose energy, and therefore your light gets shifted towards the red. This is what we call redshift, where something happens to make the wavelength of your light longer and lower in energy. But gravitational redshift is rarely significant; two other effects are far more important.
2. Redshift due to motion. If an object that emits light moves away from you, the light from it gets redshifted. This is the same exact effect -- the doppler shift -- that causes police sirens to sound lower pitched when they move away from you. One thing that's neat? If a light-emitting object moves towards you, the light gets blue-shifted, and becomes more energetic! (We see this happening for the Andromeda galaxy, one of the only ones in the Universe that moves towards us.) And although this is incredibly useful, this is not what's happening to light in the Universe. Remember, I told you that these distant galaxies aren't moving, the space between them is just expanding. Well, guess what?
3. Expanding space causes a redshift! (And thanks to av8n.com for the image!) You see, as space expands (above), the wavelengths of the light in it also expand, as you can see below.
And this last effect is so important for the expanding Universe. Why? Well, if we measure the light from many, many distant objects and determine their distances, we can -- simply based on the objects' redshifts -- learn the entire history of how the Universe expanded. The redshift isn't hard to measure, either:
It is from literally millions and millions of these individual measurements that we've been able to determine the entire history of how the Universe expanded. That, among other things, is how we discovered dark energy and the accelerating Universe! Pretty remarkable stuff, and yet, not intuitive at all.
So what should you take away from this? That as light travels through space and space expands, it causes the wavelength of that very light to expand, too. And that's how we learn about the history of cosmic expansion in our Universe. Again, it's expansion that's causing this redshift, and not motion. Hope this helps shed some light on some of the most confusing stuff out there!
Physical Science
Comments
Ha! I finally understand Gravitational Redshift now...thanks!
Posted by: Brando | August 5, 2009 3:05 PM
... and when light interact with anything (gravity, magnetic fields, "dark matter" = placeholder for anything we don't know) it will loose energy, kind of friction in mechanics: since energy and wavelength are related, redshift will happen with or without expansion of the universe
Posted by: Bernd | August 5, 2009 7:30 PM
A very clear and easily understood explanation with outstanding graphic. You clearly have a gift for teaching.
Posted by: Art | August 5, 2009 8:54 PM
I have a question. Let's say that two objects are some distance, x, apart, and a photon leaves one and heads for the other. The distance between the objects is n times the photon's wavelength, and there is no expansion of space between the objects, so the photon travels n times it's wavelength before hitting the second object. If we repeat this process but this time with expansion, then your number 3 says that the expansion of space would stretch the photons wavelegth throughout it's journey until it hit the second object with some wavelength greater than it started with. It would also travel more distance and take more time to reach it's destination than the first photon. My question is, would the photon still have travelled n wavelengths? In other words, if n1=x/lambda in the first scenario (where lambda = the photon's wavelength = constant), would n2=int(dx/lambda) = n1 in the second scenario (where lambda = f(x))?
Posted by: Trey | August 5, 2009 9:21 PM
Trey,
Only if the expansion rate is exactly a constant over time. In that special case, then yes, the number of wavelengths traveled will be exactly the same as it would've been in a static scenario.
However, in our Universe, the expansion rate changes with time. So in your theoretical case, yes, but only because you are using a constant expansion rate. Otherwise -- if you model the real Universe -- the decreasing rate that space is expanding before the photon gets there will skew your answer towards having more wavelengths than it would have in a static Universe.
Posted by: Ethan Siegel | August 5, 2009 10:02 PM
How can you differentiate the expansion redshift from the movement redshift? How can you determine that a galaxy's redshift is caused by the expansion of the Universe, and not simply by the movement of the galaxy away from us in a "solid" Universe?
Posted by: Autofocus | August 5, 2009 11:38 PM
Autofocus,
If I remember my cosmology correctly, you can't distinguish the cause of the redshift by itself, but there are several other observations that can discriminate between a static and an expanding universe. But I will defer to our good host.
Posted by: Anthony | August 6, 2009 12:35 AM
If the Andromeda galaxy is moving towards us, then some galaxies must be moving yes? You said "I told you that these distant galaxies aren't moving, the space between them is just expanding." and it has thrown me slightly. Some Galaxies must be moving yes, acting on gravity and such? If the Andromeda galaxy is moving towards us (are we also moving towards it?), then does that mean it us heading towards us faster than the rate at which the universe is expanding?
Posted by: piratebrido | August 6, 2009 2:11 AM
piratebrido: As I understand it, distant galaxies are redshifted due to the expansion of the universe. Now, these galaxies are also moving (within their galaxy clusters), but expansion is a much larger factor. The Andromeda galaxy is within our own galaxy cluster, and is actually moving on a collision course with us (in a few billion years, mind), which is why it's blue-shifted.
Note: I'm not a cosmologist.
Posted by: Joel | August 6, 2009 2:41 AM
Theoretically.... could it be true that if I go really really fast with my car, I could reach a speed were I would see the red light of the traffic light as green as I get closer and then red again as I leave it behind?. Will the traffic lights become obsolete? Should we switch the colors?
Posted by: Funtio | August 6, 2009 5:48 AM
@Joel
That's what I had thought. Just looking to get it clarified as his statement seems to suggest that distant galaxies don't move and expansion accounts for the red shift.. If distant galaxies don't move, then why does Andromeda appear to be moving against expansion towards us; what's the difference? I could be reading too much into this, but it is a facinating subject.
Posted by: piratebrido | August 6, 2009 5:51 AM
Unless it is closer to the centre of the galaxy and is expanding out with us, thus it appears blue shifted from our perception? Like looking out the rear window of a car at the car behind us?
Posted by: piratebrido | August 6, 2009 5:53 AM
I could reach a speed were I would see the red light of the traffic light as green as I get closer and then red again as I leave it behind?
Sure.
Will the traffic lights become obsolete?
I hope to heck that we're using automated controls by the time we're going that fast. ;-)
Posted by: Naked Bunny with a Whip
| August 6, 2009 6:34 AM
Galaxies are clustered into galaxy clusters and groups, and within these they revolve around a center of gravity (just as planets do). Now, there's a lot of space between those distant galaxies and us, and it's the space itself which is expanding. So, compared to the amount of movement they're doing, they are expanding away from us quite rapidly - some are moving towards us, but they're all expanding even faster away from us. Which is why they're redshifted.
Now, Andromeda is the nearest galaxy to our own, and we're both in the same galaxy cluster. So there's not "much" space between us and them, so they're not expanding away from us as fast. However, it is moving within the local group toward us, at a rate which is faster than the rate it's expanding away. Therefore, blueshifted.
Posted by: Joel | August 6, 2009 6:55 AM
Piratebirdo,
Galaxies move with what we call "peculiar velocities", which is to say that, due to the gravity of the stuff around it, each galaxy "moves" relative to the space around it at a few hundred to a few thousand km/second.
However, the Hubble expansion rate, once you get farther than about 20-30 Mpc away, dwarfs these peculiar velocities, and is [b]independent[/b] of them. It's like having a road that slopes slightly uphill with a lot of bumps in it. At first, the bumps may confuse you, but the farther up the road you go, the more you realize it's just a bumpy, uphill road. In this case, the bumps are the "motions" and the hill is the Hubble expansion of the Universe.
Posted by: Ethan Siegel | August 6, 2009 7:31 AM
This is probably a really stupid question, but I'll ask it. If light from Andromeda is blue-shifted as it moves towards us, it's gaining energy. If, however, I was on a planet in the Andromeda galaxy and I could watch that light moving away from me, would I not see it red-shifted, and thus loosing energy? Given that light is described as both a wave and a particle, how does it have both energy levels?
Posted by: John Wilson | August 6, 2009 7:39 AM
Can you distinguish between "movement redshift" and "expansion redshift" physically, or is it the "it has to be expansion because it's faster than light" argument.
Posted by: Mu | August 6, 2009 8:03 AM
John Wilson: You couldn't see light that was moving away from you. You'd see other light, also from Andromeda, which is moving towards you.
Posted by: Joel | August 6, 2009 8:06 AM
Mu, physically, "movement" leaves other signatures besides redshift. But if all you measured was the redshift of one object, there would be no way to discern.
That's really the key to understanding cosmology, is to recognize the best way to put all the puzzle pieces together. If you're a fan of equations, then conceptually, redshift works like this:
Redshift*speed of light = Hubble Expansion + peculiar motion
Since Hubble expansion is just the Hubble Constant times the distance an object is away from us, we can get this value for a very large number of objects. Whereas peculiar motion always tops out at around 3,000 km/s, we can measure redshifts for objects with distances that are megaparsecs, 10s of megaparsecs, 100s of megaparsecs, and gigaparsecs away!
By time you get out to 100 megaparsecs or more, the peculiar motion is insignificant, and so we know we're looking at expansion. It also helps that it's the same rate everywhere in space *and* in all directions. Other explanations can be made to fit the data, but they are contrived (i.e., they place us -- and nobody else -- exactly at the center of the Universe).
Posted by: Ethan Siegel | August 6, 2009 8:50 AM
Thanks Ethan, that makes sense.
Posted by: Mu | August 6, 2009 10:11 AM
When figuring the expansion rate do you have to subtract the red shift due to the gravity of the galaxy the light is coming from? Or does the gravity well have to be black hole sized before it matters.
Posted by: the backpacker | August 6, 2009 11:42 AM
This is the best blog on earth, hands down.
Posted by: Magpie | August 6, 2009 9:02 PM
I have a question regarding the expanding universe redshift. Where can i find out more as to why an expanding universe causes or influences the expansion of wavelengths, and are there measurable effects for wavelengths above and below the visible spectrum?
Also, what books would you recommend to a beginner for gaining a theoretical grasp of physics and/or basic astrophysics (My last formal class in physics of any sort was before i started studying logistics at the university, with the exception of statistical analysis)?
Finally, another question: is it possible that an expanding universe may also cause particles to expand in any way?
Thank you for writing this blog. I am an avid (if occasionally lost) reader, and your blog is one of the few theoretical physics outlines on the net where i can read about astrophysics and "cool stuff happening in space" that i can follow without a graphing calculator in one hand and a theoretical maths textbook in another.
Please keep on writing; i assure you i will keep on reading.
Posted by: dumbassnoob | August 12, 2009 10:39 PM
Ooppss!... I've been lazy and only now I translated it into Brazilian-Portuguese here.
Sorry, Ethan!...
Posted by: João Carlos | August 14, 2009 7:04 PM
The Economist recently published this item:
Correction: In "As important as Darwin" published on August 15th, we said that no astronomer can look beyond a distance of 13.7 billion light years. This was incorrect. The universe has expanded during the 13.7 billion light years that light has been zipping across it and, as a consequence, astronomers can see to distances of perhaps as far as 47 billion light years.
I'm baffled. Isn't the universe about 13.7 billion years old? How can anyone look back 47 billion light years? Will someone please comment on the issue, which seems to fly in the face of the usual view that we can peer back some 13 billion years or so to the earliest galaxies, but no further than that.
Posted by: Colin Norman | August 29, 2009 3:57 PM
If we were in a galaxy near the edge of the universe and looking toward the edge, would we see darkness or would we see a "mirroring" of our own universe? If so, would the mirrored light be red-shifted further than if we looked directly at it?
Posted by: Steve Clay | October 17, 2009 7:36 PM
@Colin: The correction had its own error: "The universe has expanded during the 13.7 billion light years..." They mean years (a time period) not light-years (a distance).
You're correct: No photons are older than 13.7B years, but many of them have traveled farther than 13.7BLY (the distance). Expansion is like upgrading from a 14" TV to a 47" TV in the middle of a baseball pitch: The pitch doesn't take longer but the ball (photons) now has gone farther across your living room.
Posted by: Steve Clay | October 17, 2009 7:52 PM
As I understand it (or don't) space expands in a proximate to gravity sources. If this is so, is "color" affected by gravity proximate to the observer in a "condensing" phenomena, as it was in the expanding areas? I'm not even an undergraduate, so I'm not sure this question is even meaningful.
Posted by: Jim Gentry | July 16, 2010 2:02 PM
@23
No, expansion does not affect sub-atomic particles. infact it doesnt even affect our solar system. As far as we know subatomic particles can neither be made any larger or smaller then they already occur in nature. The force that binds electrons to neutrons is called the strong force b/c it is the strongest force of the four.
FORCE: RELATIVE STRENGTH:*
Nuclear (aka strong) 10^3
Electromagnetic 1
Weak 10^-11
Gravitational 10^-39
*The relative strengths are given in exponential numbers, where 10^3 stands for 1,000 and 10^-11 for 1/100,000,000,000.
Table taken from The Collapsing Universe by Issac Asimov pg. 2
As I understand, the expansion cannot exert itself on individual particles (if it could we'd all be dead).
On a grander scale u can imagine the individual galaxy's within a galaxy cluster being held together by springs (springs= their gravity) so the dark engery (expansion) has a hard time expanding the space b/w the galaxies b/c of thier gravity. (I'm far from an expert and am probably wrong)
Hope that helps somewhat.
Posted by: crd2 | July 16, 2010 4:26 PM
If Andromeda is coming towards us, then where is the center of the universe? Back behind andromeda? That is where the big bang originated? Is that we all can go to heaven? big grinn
Posted by: BKK Willy | March 29, 2011 1:06 PM
Thank you so much for explaining redshift in such a simplistic way! I wish there were more people like you that teach Science!!!!!!
Posted by: Rhonda Cox | April 3, 2011 7:32 PM
I have read that about 3% of the volume of the universe is estimated to consists of galaxy clusters/super-clusters. Since these are bound structures, they do not participate in space expansion. This means however that a photon should be in a region of non-expanding space for about 30% of the time (volume = (linear distance)^3) and the redshift should thus be 30% less as well. However, I have not seen this issue addressed anywhere when it comes to redshift-distance calculations.
Thomas
Posted by: Thomas | May 2, 2011 5:42 AM
Thomas
I see your site (Physics Myths and Physics Facts,Flaws in Concepts and Theories of Modern Physics) and I'll go through it carefully.
At any rate, let me suggest that you are asking the wrong question.
Ethan says, "Now there are.. only three things.. that can happen to this light to change the wavelengths... 1. Gravitational Redshift... 2. Redshift due to motion... 3. Expanding space causes a redshift!" OK so far.
But as well, Ethan says, "But gravitational redshift is rarely significant." And with similar few words everyone, without a single calculation, for nearly the last 80 years has dismissed gravity as a redshift explanation.
But the gravitational redshift is of sufficient magnitude to account for the observed redshifts described by Hubble's law. Follow the links of my name to read page 36 to 39 of A Critigue of Pure Physics. It is fully readable online at google books.
There you will find a simple calculation that shows that indeed gravity is sufficient to account for the Hubble redshift.
Posted by: Thomas Neil Neubert | May 2, 2011 4:20 PM
Thomas
I see your site (Physics Myths and Physics Facts,Flaws in Concepts and Theories of Modern Physics) and I'll go through it carefully.
At any rate, let me suggest that you are asking the wrong question.
Ethan says, "Now there are.. only three things.. that can happen to this light to change the wavelengths... 1. Gravitational Redshift... 2. Redshift due to motion... 3. Expanding space causes a redshift!" OK so far.
But as well, Ethan says, "But gravitational redshift is rarely significant." And with similar few words everyone, without a single calculation, for nearly the last 80 years has dismissed gravity as a redshift explanation.
But the gravitational redshift is of sufficient magnitude to account for the observed redshifts described by Hubble's law. Follow the links of my name to read page 36 to 39 of A Critigue of Pure Physics. It is fully readable online at google books.
There you will find a simple calculation that shows that indeed gravity is sufficient to account for the Hubble redshift.
Posted by: Thomas Neil Neubert | May 2, 2011 4:43 PM
The following are the explanations why the discovery of Edwin Hubble does not provide a good evidence that our universe would be expanding currently:
a)Despite many red shifts through telescope from astronomers, it does not provide the proof that this universe could be expanding for the following reasons:
1) The possibility that our universe could be very huge that it would take more than trillion of years to reach the opposite end of the unverse (sphere). The assumption is based upon the following factors: This universe is assumed to be as a shape of sphere with external boundary and all galaxies are assumed to move within the boundary of this universe.
Let’s imagine you stand at one end of the sphere (the universe) to have a full view of all the surrounding movement of galaxies. As all the galaxies were advancing at a high speed from your end to the edge of the sphere that is right opposite from you that form a half complete round, you certainly would visualize that all the galaxies are advancing as if that they are leaving away from you since their movement in speed is a few time faster than your galaxy. As this universe is very huge so much so that it would take a very long time, let’s say, more than a trillion years to reach the point that is right opposite to the point so as to make a half complete turn of this universe. Despite many galaxies have been moving towards the point that is right opposite to the point where you are viewing through telescope, the result would turn up to be many red shifts to have appeared in the universe. As universe is too huge for galaxies to travel from one end to another and only a few have completed a half turn to move than to the starting point of the sphere where you are to the edge of the sphere that is right opposite from you, it turns up that they are many red shifts than blue shifts.
2) The second possibility is that many galaxies might have advanced faster than us and yet many galaxies might have made a complete half turn within the sphere (the universe) and yet the galaxies might not as what we think that they would keep on rotating themselves in a circle. Instead, they might not return to the previous track where they have passed through. These could result that they do not turn back to us.
3) The third possibility is that all the clusters of galaxies could be advancing in the same place and same direction just that most of the galaxies are advancing faster than us as if that their galaxies are moving further away from us. As we are in this tiny world and cannot have the full sight of this universe, we could not reject this possibility since it might be so without our full view of this universe since the astronomers just looked at the sky with a telescope that comes to their conclusion without viewing the universe as a whole. No matter how advance is the technology, it could never be possible to build an advice that could capture the whole view of universe from one end (the earth).
4) The fourth possibility is that majoirty of the galaxies might have made a full complete turn in this universe within the boundary of the universe in many years ago, such as, more than a few thousand years ago. Or in other words, there might be a time in the past in which there were many blue shifts than red. What the astonomers that have seen right now with many red shifts do not reflect the universe might be expanding since there might be a period of times in many years ago that almost all the galaxies have made a complete full turn and it turns up that many galaxies have turned up to be red shifts currently. Or in other words, it would take many years later, such as more than a few thousand years later, in order to have many blue shifts instead of red shifts at that time.
5) The fifth possibility is that universe was created in infinity and that all galaxies are advancing ever since the past. If that is so, it is erroneous to use many red shifts as discovered by astronomers to conclude that the universe is expanding.
There might be other possibilities that you could think of why there are more red shifts than blue shifts and yet it does not come to the conclusion that the universe is expanding. As there are many alternative possibilities, to jump into conclusion that the universe is expanding through many red shifts being discovered is rather a little speculation.
Posted by: Li Kong | August 16, 2011 1:27 AM
The reasons why the discovery of Edwin Hubble does not prove that our universe could be expanding:
Despite his discovery about many red shifts in the galaxies through observations instead of hypotheses or theory drawn from the data, there is a shortfall in his discovery. This is due to his observation about many red-shifts in the galaxies was throughout his limited span of life instead of throughout generations from generations since it might take many years, let’s assume more than 1000 years or even higher, in order to get all blue shifts at that time.
There could be a possibility that there were many blue-shifts in the past, let’s say, more than a few hundred years ago, due to many galaxies might have made a full turn at the same time. As many galaxies might have made a full turn in the past, the current view that galaxies have shown many red shifts do not reflect that the universe is expanding.
As we are living in this small little earth, our perception through telescope could not give a full view pertaining to the situation about how our universe is responding.
Edwin Hubble mentioned that the universe is expanding as if there is a boundary in this universe. If there could be no boundary that could restrict the universe, the universe should be in infinity. As we do not have a full view of the universe as a whole, to mention that this universe is expanding is little speculation in the sense that we do not know whether the universe could be in infinity or not.
For instance, if this universe were in infinity, there should not be any reason for us to mention that this universe is expanding. Many red-shifts that the astronomers gather from galaxies could only show that many galaxies are advancing further away from us and it does not reflect that our universe is expanding since the universe is in infinity.
For instance, if this universe could have a finite space, it is rational to assume that there should be a boundary to restrict the space of this universe. If there could be no boundary to restrict the space of this universe, how could there be a finite space in this universe? If there could be no boundary in this universe, how could the astronomers presume that the universe is expanding by seeing many red-shifts in the galaxies? To jump into the conclusion that the universe is expanding without realizing whether this universe has a finite space is a little speculation.
If this universe has a finite space, it is rational to assume that this universe should look like a sphere or a sphere with oval shape. It is irrational to assume that this universe should look like cube or rectangular shape or whatever. To assume that the universe would look like a sphere, is simply an illustration so to give the possibility of why red shifts do not reflect the truth that the universe is expanding. We could not have a full sight of this universe whether there could be a boundary. What if the universe does have the shape of sphere in reality, giving an example that this universe as a sphere would be the most appropriate approach. As we could not have the full sight of this universe, to jump into the conclusion by seeing many red-shift is rather a little speculation.
Posted by: Jason Tannery | August 17, 2011 7:05 PM
Edwin Hubble mentioned that the universe is expanding by observing the existence of many red-shifts appear in the galaxies is itself an assumption. One might argue that the universe is not a sphere and that we have no proved to deny it since nobody in this earth did see the boundary of the universe. Some might assume that there is no ‘empty place’ in the universe into which matter expands. If that is true that there is no ‘empty place’ in the universe into which matter expands, questions have to be raised due to the uncertainty about what would go beyond the matter in which the universe itself is expanding: What materials could it be that would make up of that materials? Nobody in this world has ever seen in the past whether there could be any matter that covers the universe. So, nobody in this world would know whether the matter could be stretchable or non-stretchable. What if the matter that covers the universe is not stretchable, how could the assumption that the universe could be expanding to be true? By the way, as nobody could see that there could any matter that covers the universe and this includes Edwin Hubble. His theory that the universe is expanding by observing many red-shifts in the galaxies is just some kind of speculation. If there could be matter beyond the matter, how big could the matter be? Could there be anything or any other universe or anything that is beyond this universe that could block the expansion of this universe in many years later? What could that matter be made up of so much so that it could allow this universe to be expandable? If that could be some matter that covers this expanding, could the thickness of this matter be lasted into infinity? If there could be a matter that covers this universe, could this matter be breakable since the support that the continuous expanding of this universe is true? Would there be any substance after the matter that covers the universe that could be expanding? As there are many uncertainties about this universe and whether there could be any matter that covers this universe since nobody could have a full sight of this entire universe, Edwin Hubble jumps into the conclusion that this universe is expanding by seeing many red-shifts in the galaxies is a little speculation unless he could be certain that there were people in the past did see the matter that would cover the universe so as to make this conclusion. Or else, there could be a possibility that this universe might be lasted until infinity without any matter covering this universe.
Posted by: Li Kong | August 17, 2011 9:25 PM
Edwin Hubble’s theory does not provide any support for the Big Bang’s theory since his theory involves speculation since we do not have the full sight of how this entire universe could look like.
Is it true to mention that there is no blue shift in this universe? The following are the websites addresses in which you could locate evidences that there are blue shifts in the galaxies to disprove the argument:
http://ned.ipac.caltech.edu/cgi-bin/nph-allsky?ra_constraint=Unconstrained&ra_1=&ra_2=&dec_constraint=Unconstrained&dec_1=&dec_2=&glon_constraint=Unconstrained&glon_1=&glon_2=&glat_constraint=Unconstrained&glat_1=&glat_2=&z_constraint=Less+Than&z_value1=0&z_value2=&z_unit=km%2Fs&ot_include=ANY&ex_objtypes1=Clusters&ex_objtypes1=Supernovae&ex_objtypes1=QSO&ex_objtypes2=AbsLineSys&ex_objtypes2=GravLens&ex_objtypes2=Radio&ex_objtypes2=Infrared&ex_objtypes3=EmissnLine&ex_objtypes3=UVExcess&ex_objtypes3=Xray&ex_objtypes3=GammaRay&nmp_op=ANY&out_csys=Equatorial&out_equinox=B1950.0&obj_sort=RA+or+Longitude&zv_breaker=30000.0;
http://www.beskeen.com/gallery/galaxy/m31/m31.shtml
The following are the possible reasons for the above blue shifts to arise:
a) This universe could have an immense space in which it might take more than 12 billion light years or even trillion light years to travel from one end of the universe to another initially. These galaxies might have travelled more than a half round in their usual routine tracks of rotation to its return and that there could be a possibility that there were a period of long time and that could be more than 12 billion light years ago that most of the galaxies might be in blue shift. As some of the galaxies are advancing slower than majority of the galaxies, it turns up that majority might have completed their full turn and moving upward and advancing further away from us and leaving a few galaxies to be in blue shift currently. As nobody could see the universe as a whole from the very past, especially what was beyond 12 billion light years ago or even trillion years ago, there could be such a possibility to occur in this universe. To jump into the conclusion that this universe is expanding simply by seeing many red shift is rather speculative.
b) There could be a reason in which that all the galaxies might have travelled faster than the above-mentioned galaxies bypass our galaxies in numerous years ago and ultimately causes these galaxies to fall behind due to their rotating speed is slowly than most of the galaxies. This assumption includes the possibility that there could be many blue shifts in numerous years ago and that could be beyond 12 billion light years ago, as the galaxies were travelling a rapid speed toward us. As most of the galaxies have bypassed our galaxies in the past and at the same time they have completed a full turn from its rotation, these certainly result in many red-shifts in current world due to most of the galaxies have moved upward following its usual movement tracks for its half turn of its rotation. As a result, this causes us to have more red-shifts than blue currently.
Most of the galaxies might not pass through us to be the centre of the point for rotating. However, it could be the possibility that most of the galaxies could have bypassed us in numerous years ago and this could be the reason to have the result in many red shifts than blue currently.
As some of the galaxies were moving slower than most of the galaxies, this results that there are more red-shifts than blue currently.
c) There could be a reason that some galaxies are moving fastest speed than the other and this causes some galaxies to be in blue shift since they have completed a half round turn in facing our universe in advancing.
d)There could be many other possible reasons that we could think of for the possibilities to have more red-shifts than blue currently and that does not come to the conclusion that our universe is expanding or this universe could create something out of nothing.
Some might mention that the discovery of many red shift in the galaxies have moving further away in rapid speed, could provide the support of dark matter theory or Big Bang theory. However, there is a possibility that most of the galaxies might well perform their routine movement and it might not give any signal that this universe could be expanding. As most galaxies are travelling in rapid speed, this causes them to bypass us fastest than a few galaxies and this has resulted in more red shifts than blue currently.
Some might have mentioned that the observation could be through 12 billion light years old that the galaxies have been moved in all directions further away from us. However, consideration has to be taken into accounts pertaining to the size of the universe since the size of the universe could be so immense that galaxies might take more than 12 billion light years or even much longer than that, such as, a few trillion years in order for galaxies to make a half turn in rotation in order for us to have most of the galaxies to be in blue shift. As nobody could have the full view of this universe and nobody did see whether there could be a boundary of this universe, we could not reject the possibility of the vast space of this universe. Or in other words, there could be a possibility that galaxies might take more than 12 billion light years or even trillion light years in order that most of the planets could complete their half round turn so that we could have the many blue shift from that time onwards.
Nevertheless, it is irrational to jump into the conclusion that the universe is expanding simply by observing the galaxies are advancing further away from us to conclude that our universe is expanding.
Posted by: Jason Tannery | August 19, 2011 6:15 PM
Some might argue that there is no boundary in this universe and yet the universe could be expanding to support the Big Bang theory. There are a number of questions have to be raised:
a)As nobody in this world in the past has seen there is a restriction in the space of universe, how could we be so sure that this universe could be in limited space for this universe to expand?
b)As there could be no boundary in this universe and there has been no eye-witnessing that our universe could be restricted in space, how could we be so sure that there could be place for this universe to expand?
c)As there could be no boundary in this universe and there has been no eye-witnessing that this universe could be restricted in space, how could we be so sure that this universe could be expanding since nobody could have eye-witnessed that this universe could be limited in space and that causes it to be able to expand further or even until eternity?
d)As there could be no boundary in this universe and there has been no eye-witnessing that our universe could be restricted in space, how could we determine the diameter of this universe?
e)As there could be no boundary in this universe and there has been no eye-witnessing that our universe could be limited in space, what yardstick has been set to determine that this size of this universe or whether this universe could be itself in infinity?
Posted by: Li Kong | August 19, 2011 9:10 PM
The following are some of the explanation pertaining to the websites address from : http://www.physlink.com/education/askexperts/ae384.cfm pertaining to the reply of blue-shift:
The fourth paragraph of the reply as listed in the above website address has been listed here for discussion:
A useful analogy here is to take an empty balloon, draw dots all over it to represent galaxies, and pretend that we live on one of the dots. As you blow up the balloon, ALL of the dots move apart from each other. And the ones that are farthest away from us move the fastest.
There are some discrepancies between balloon and the galaxies in which balloon might not be suitable to be used to support Edwin Hubble’s theory:
a)There is a visible boundary in the empty balloon and that is the plastic that is made up of that balloon. However, we do not know whether there is any boundary in this universe or whether this universe could be itself in infinity and there could be no way to talk about expansion since there could be no limited in space. Even if there is a boundary that covers the universe, we do not know what matter that is made up of that boundary. The example that is used for balloon is plastic. The plastic is indeed stretchable. However, we do not know even whether the boundary of this universe is stretchable. As you continue to blow the plastic balloon, it would soon burst. This should not be applicable to the universe. As there are discrepancies between balloon and the uncertainty whether there could be a boundary of this universe, it is irrational to use balloon as an illustration to support Hubble’s theory.
b) As we blow the balloon, all the air would go into one direction to cause the balloon to expand. However, there are a few galaxies are in blue shift that could not go adversely. As there are discrepancies between balloon and this universe, how could we use balloon for the illustration of this universe?
c)As we blow the balloon, all the air would go into one direction. If we assume that there is a strong force from the centre of the earth to blow in all its surrounding, certainly all the galaxies in the surrounding would move farthest away from this earth. As there is a continuous force to push from the centre of the earth to other surrounding galaxies, all galaxies whether they are near or far would move farthest away from the earth and there should not be any reason for some galaxies to have blue shift. This assumption is simply using the earth as the centre to be the force to cause other galaxies to advance away from us.
Let’s assume that the force has come from one of other galaxies far away from us. The force that is directed would cause other galaxies and these include our galaxy to advance further away from that galaxy. Or in other words, our galaxy would also be advancing instead of merely other galaxies. As the force might not be from us and it might be from one of other galaxies, our earth could not be assumed to be the centre to the force to cause other galaxies to move. If that could be so, there should be many blue shift at all time instead of many red. Thus, the assumption that the force could be come from one of other galaxies to cause galaxies to advance could not be acceptable in Hubble’s law.
Nevertheless, it seems to be that Hubble’s theory could not be acceptable if we could use the earth to be the centre as a force that causes the surrounding of the galaxies to advance further. However, there is a shortfall in Hubble’s theory since why blue shift should appear then.
d)As we blow the balloon, all the particles in the balloon is moving in one direction in a constant speed. Let’s assume that there is a force that causes other galaxies to move farthest away from us. There are a few queries to be raised: As there is a constant force to cause the galaxies to be expanded and this has resulted that the galaxies should move farthest away in constant speed from us, why is it that some galaxies could move faster than the other? If there is a force to cause our galaxies to be expanded and this has resulted that the galaxies to move further away from us, our galaxy should indeed join the queue in advancing instead of stationing here and many of other galaxies seem advancing further away from us except that we are not advancing further.
Posted by: Jason Tannery | August 20, 2011 10:13 PM
Some might mention that they have photos of stuff occurring about 14 billion years ago to support Edwin Hubble’s theory that there were many red-shift in the galaxies in the past. However, there are two possibilities that many red shifts that have appeared about 14 billion light years might not give the proof that this universe could be expanding:
a)There could be a possibility that the universe itself is not expanding. The original size of the universe could be so huge that it might take more than a few trillion light years for galaxies to travel pass from one end of the universe to another. As the size of the universe might be very huge so much so it would take more than a few trillion years for galaxies could be very huge, it turns up that the galaxies would take about 14 billion years to travel and yet they have not yet reach nearly the end of the galaxies in order to make a turn for their return in advancing towards us. As a result, there shows more red-shifts than blue currently. Or in other words, there would be a time in which there could be more blue shifts than red and it should be at more than a number of billions of light years later in which most of the galaxies have completed their half round of travelling in turning to us for advancing.
b)There could be a possibility that the universe could be advancing as supported by Edwin Hubble.
c)There could be a possibility that the universe could be lasted until infinity. If there is no boundary or space limit for this universe, many red-shifts that have discovered in the past would not give us the information that the universe could be expanding due to our universe could be lasted until infinity and there is no space limit at all.
As there are two out of three possibilities that could not come to the conclusion that many red shifts in the galaxies that had been discovered by Edwin Hubble could come to the conclusion that this galaxies could be expanding, to jump into the conclusion that the universe is expanding is rather speculative.
Some might comment that we could compute the size of the universe in miles from the age dimension to conclude that the size of the universe could be measured. However, by tracing the years backward in which red shifts have been advancing would not tell the size of the universe since it only could tell the number of years from now to then. It could not tell whether there could be size from the galaxies and that is beyond. For instance, if the universe could be lasted to infinity, the method that has been adopted to compute the size of universe would not turn up to be accurate.
Posted by: Li Kong | August 23, 2011 3:13 AM
"and yet they have not yet reach nearly the end of the galaxies in order to make a turn for their return in advancing towards us. As a result, there shows more red-shifts than blue currently."
Sorry, doesn't make a blind bit of sense.
If you're talking about redenning because of dust in the way, then this reduces the blue component but doesn't cause the absorption spectra to change.
But maybe you mean something else. In either case, this statement makes no sense.
"c)There could be a possibility that the universe could be lasted until infinity."
However, work done requires a temperature difference. And therefore your universe started 14 billion years ago will get less and less active. This is the heat death of the universe.
It isn't, however, an alternative to point b.
"However, by tracing the years backward in which red shifts have been advancing would not tell the size of the universe"
Another statement that makes no sense.
We don't see red shift advancing. We see wavelengths of light shifted to the red.
"For instance, if the universe could be lasted to infinity, the method that has been adopted to compute the size of universe would not turn up to be accurate."
Sorry, no. It can last for another infinity years, but this doesn't mean it always lasted infinity years in the past.
What makes the age of the universe difficult is the definition of the distance to galaxies, which depend on certain types of supernova to be visible AND of (somewhat) predictable nature. Taking the apparent magnitude and knowing the brightness of the supernova you can work out the distance.
IF you are accurate in determining the type of supernova.
And IF you account for intervening matter dimming the light (and, oddly enough, making it redder).
Posted by: Wow | August 23, 2011 6:46 AM
"b) As we blow the balloon, all the air would go into one direction to cause the balloon to expand. However, there are a few galaxies are in blue shift that could not go adversely"
Galaxies too move in the universe. And the expansion close to us is very low. Therefore a galaxy close to us and moving toward us will show a blueshift, despite a redshifting expansion of the universe.
Posted by: Wow | August 23, 2011 6:50 AM
"There are a few queries to be raised: As there is a constant force to cause the galaxies to be expanded"
There's no force. Not on our universe, anyway. The balloon is expanding. There is no force on the dots of the balloon (no force in our universe), just expansion of that universe.
"and this has resulted that the galaxies should move farthest away in constant speed from us,"
This isn't the case. The more distant a galaxy, the more space there is currently between us. Since space is expanding, there's more expansion to that distant galaxy. Since there's more expansion, there's more redshift.
"why is it that some galaxies could move faster than the other?"
Because they're moving on the "surface" of the balloon. That gets added to the velocity we interpret from the redshift.
Posted by: Wow | August 23, 2011 6:53 AM
"But as well, Ethan says, "But gravitational redshift is rarely significant." And with similar few words everyone, without a single calculation, for nearly the last 80 years has dismissed gravity as a redshift explanation."
However, since we're deeper in the gravity well, the red shift would be a blue shift. The photon gains energy.
There's a reason why it's been dismissed for 80 years.
Posted by: Wow | August 23, 2011 6:55 AM
The following is the website in which the calculation of the size of universe has been mentioned:
http://curious.astro.cornell.edu/question.php?number=151
The following are the verses quoted from the above websites:
My bright teenage son, after considerable calculation, has concluded that the universe is approximately 68 sextillion miles wide. He based his calculation on the basic 186K mi/sec speed of light x the estimated 15 billion year age of the universe.
There are a few shortfalls in above computation of the size of the universe:
a)It is a clear cut from the explanation above that the computation of the size of the universe is subjected to the travelling speed of 184 mi/sec speed of light for the movement of the galaxies. However, there is a limitation in the computation of the size of the universe and that is the computation does not take into consideration whether there could be a possibility that this universe could be in infinity and there could be no space limit after its formation. For instance, if size of our universe that has been formed could be in infinity and there would be no space boundary and space limit, the computation of the size of the universe would turn up to be speculative. This is due to we could not use the speed of the advancement of the galaxies farthest away from us to monitor the size of the universe due to the universe could have already been formed in infinity ever since its creation and there could be no reason for the universe to extend further since there could be no space limit in the first place.
b)It is irrational to use the estimated age of the universe as a guideline to determine the size of the universe since there could be a possibility that the size of the universe could have been formed initially with its extension to infinity. If the size of the universe could have been formed initially with infinity, there should not be any boundary or space limit for this universe to extend further since the initial size of this universe could have already been extended to infinity. To fix the age of the universe in the computation of the size of the universe, would not determine the exact size of the universe since the size of it could have been lasted until infinity initially.
Despite Edwin Hubble could produce the photos to prove that many red shifts in the galaxies ever since the commencement of the universe, to jump into the conclusion that the universe could be expanding is rather speculative for the following reasons:
a)One possibility is that this universe might have been created initially with boundary and yet the size of the universe might be so immense that it might take more than a trillion years for the galaxies to travel from one end of the universe to another. As the size of the universe could be so immense that galaxies would take more than a trillion years to travel from one end to another, it turns up that most of the galaxies are advancing further away from this galaxy due to they would take many more years to complete their half turn in order that these galaxies would turn back to us in rotation to show majority to be in blue shift in the future. That could be the reason why there are many red shifts than blue. This possibility is there since nobody ever really sees that there could be a boundary in the galaxies.
As nobody has ever seen the boundary of the universe, we could not deny that there could be a possibility that the universe could be so huge that it would take more than a trillion of years for galaxies to travel from one end of the universe to the other end.
As nobody has ever seen the boundary of the universe, there is no support that the size of the universe could not be so immense that it might take a few trillion light years to travel from one end of the universe to another.
If this universe could be so in reality, many red shifts in the galaxies do not reflect the universe could be expanding since the galaxies would take more than a few trillion of years to travel farthest away from our galaxy before they could make a u-turn so that we could have the view of many blue shifts since then.
b)Second possibility is that this universe might have been created initially with infinite space. Or in other words, there could be no boundary or space limit in the universe ever since its creation. As there could be no space limit in this universe, the observation that there have been many red shifts than blue ever since 15 billion light years ago would not give us the information that this universe could be expanding.
As nobody has ever seen there could be a boundary of the universe, there is no support that there could be any boundary in this universe. Or in other words, we could not deny that there could be a possibility that the universe could have been created in infinity and that this universe could be without space limit initially.
If this universe could be so in reality, many red shifts in the galaxies do not reflect the universe could be expanding since the universe itself could be in infinity and there could be no space limit.
c)Third possibility could be as what was described by Edwin Hubble that the universe could be expanding.
As there are two out of three possibilities that could not come to the conclusion that the universe could be expanding, to jump into the conclusion through many red shifts in the galaxies is a little speculative.
The reason why Fred Hoyle defended steady stage and yet later supported the expansion was merely due to many red shifts in the galaxies. However, there are other possibilities that might not come to the conclusion that the universe could be expanding simply by observing many red shifts in the galaxies ever since the creation of the universe.
Posted by: Li Kong | August 25, 2011 9:45 PM
A red shift would also occur if c is decelerating. This could also explain the greater amount of red shift from the most distant bodies.
Posted by: Russell crosby | January 23, 2012 9:25 AM