Galaxies recede faster than light

In summary, based on an article in Scientific American March 2005 addition, it was stated that galaxies recede faster than light. This is due to the recession of a galaxy being directly proportional to its distance from us, with the Hubble constant as the proportional constant. This constant explains how fast space is stretching, not just around us, but around any observer in the universe. This phenomenon is known as Hubble's Law. While it may seem impossible for light to pass the Hubble distance and travel faster than the speed of light, it is actually consistent with some scenarios in General Relativity. The expanding universe and the constant speed of light do not create a barrier, and there is no point in the universe where the laws of physics change
  • #1
Seeruk
6
0
This is my first post on this message board. So if this message does not represent itself the way I am trying to express it, I apologize in advance.

Based on an article in Scientific American March 2005 addition, it stated that galaxies recede faster than light.

"The recession of a galaxy away from us (v) is directly proportional to its distance from us (d), or v = Hd. The proportional constant, H, is known as the Hubble constant and qualifies how fast space is stretching - not just around us but around any observer in the universe."

This is my views from what I gathered from different sources:
This is Hubble's law. It goes on to say that when a galaxy travels in space it increases in speed as it nears the Hubble distance. The Hubble distance is a curve in space where light exists on one side and not the other. The Hubble distance barrier is not constant, it continues to move further outward. The relative Velocity of space increases as space expands constantly. Where light occurs on one side of the Hubble distance, the laws of physics take place. On the other side the laws do not take place. Once light passes the Hubble distance it now moves faster than the speed of light. Thus if light can not be seen or subject to physics, it can not be measured. This may be why Einstein said nothing can move faster than the speed of light. If the Hubble distance is not constant, than if the barrier moves behind the Galaxy that is already going faster than the speed of light it would now be behind the Hubble distance and subject to the laws of physics and Einstein's concept. Would it not be Galactic chaos? The force on the Galaxy going from faster than to slower than the speed of light would be tremendous. An example supporting my hypotheses is a toy top. As it spins it gains speed,as you continue to spin, it will gain enough momentum to move. If a force comes in contact with the spinning object it causes a negative reaction in the tops movements. Thus the object becomes unbalanced and unpredictable. I believe, the same effect should happen to Galaxies. Why does this not occur.
-Seeruk
 
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  • #2
Seeruk said:
Once light passes the Hubble distance it now moves faster than the speed of light.
Is it possible for light to "pass" the Hubble distance -- or does the Hubble distance serve as a "limit" for the movement of light toward it ? Also, see these links for recent experiment that has documented that "light" can travel faster than speed of light:
http://www.scienceblog.com/light.html [Broken]
http://www.livescience.com/technology/050819_fastlight.html
as well as "solitons": (defined here: http://en.wikipedia.org/wiki/Soliton[/COLOR]) [Broken]
http://prola.aps.org/abstract/PRD/v63/i12/e126004
 
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  • #3
For what I can find out light passes the Hubble distance. They say recession velocity can move faster than light and it still does not violate the special relativity rule. It is also mentioned that it is still true that nothing can overtake a beam of light.

Thank you for the links Rade and I hope this answers your questions.
 
  • #4
i thought nothing can exceed the speed of light?
 
  • #5
vincentm said:
i thought nothing can exceed the speed of light?


(Sigh) We should have a FAQ on this. How many times has this question been asked.

The galaxies are not moving through space away from us, the space between us and them is expanding. This is not a velocity and it can happen so fast that the distance between us and the galaxies increases faster than light, but nothing is moving faster than light.
 
  • #6
selfAdjoint said:
(Sigh) We should have a FAQ on this. How many times has this question been asked.

The galaxies are not moving through space away from us, the space between us and them is expanding. This is not a velocity and it can happen so fast that the distance between us and the galaxies increases faster than light, but nothing is moving faster than light.
Thanks, that makes perfect sense. It's kinda like this image explains.
http://www.leyada.jlm.k12.il/proj/black/images/inflate.jpg [Broken]
 
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  • #7
Seeruk said:
Based on an article in Scientific American March 2005 addition, it stated that galaxies recede faster than light.

"The recession of a galaxy away from us (v) is directly proportional to its distance from us (d), or v = Hd. The proportional constant, H, is known as the Hubble constant and qualifies how fast space is stretching - not just around us but around any observer in the universe."

Welcome to PhysicsForums, Seeruk!

The situation as described above is accurate. It is important to realize that many articles and discussions of physics necessarily use shorthand terminology. Such terminology is often later used out of context. So you need to make sure you are working within the right context before you can expect to understand it.

General Relativity (GR) is the theory used to describe the interaction of spacetime and mass. While there are a few things which are not known about cosmology and GR, there are many that are known. The discovery of galaxies receding at speeds much faster than the speed of light (c) has led to this realization: our universe is not flat but is actually expanding at an accelerating rate. This is completely consistent with some GR scenarios.

It may seem impossible, but light from such receding galaxies can reach us even though the speed of the light particles does not ever exceed c locally. The details of this are fairly complicated, and a reference can be provided if you want to read something technical.

I would not think of the Hubble distance as some kind of curtain beyond which we cannot see. There is no point in our universe at which the laws of physics change (that we know of) or that c is different. Keep in mind that c is a constant value describing the speed of light particles in a "vacuum". The speed of light in varying mediums can be modified as described in some of the references above; however, that does not change the value of c.
 
  • #8
It is explained here, again. And, for those who haven't, please go to the top of the page and read the whole FAQ. That will help keep the number of questions about the basics at a minimum
selfAdjoint said:
.(Sigh) We should have a FAQ on this. How many times has this question been asked.

The galaxies are not moving through space away from us, the space between us and them is expanding. This is not a velocity and it can happen so fast that the distance between us and the galaxies increases faster than light, but nothing is moving faster than light.
is right on.
 
  • #9
selfAdjoint said:
(Sigh) We should have a FAQ on this. How many times has this question been asked.

The galaxies are not moving through space away from us, the space between us and them is expanding. This is not a velocity and it can happen so fast that the distance between us and the galaxies increases faster than light, but nothing is moving faster than light.

While I agree with most of this, its important not to disregard the motions of galaxies as simply a byproduct of the Universes expansion.

'Space-time expansion' is a dubious concept. How do we know 'space' is expanding without matter? By definition, space can not even be measured without the existence of objects: thus, the 'expansion of the universe' is infered from the motions of matter. In GR, the very existence of space is redefined as the relations between interval-events.
So saying 'it is space which expands' is not entirely correct, since space (or time) cannot exist of itself.
 
  • #10
Seeruk said:
This is my first post on this message board. So if this message does not represent itself the way I am trying to express it, I apologize in advance.

Based on an article in Scientific American March 2005 addition, it stated that galaxies recede faster than light.

"The recession of a galaxy away from us (v) is directly proportional to its distance from us (d), or v = Hd. The proportional constant, H, is known as the Hubble constant and qualifies how fast space is stretching - not just around us but around any observer in the universe."

This is my views from what I gathered from different sources:
This is Hubble's law. It goes on to say that when a galaxy travels in space it increases in speed as it nears the Hubble distance. The Hubble distance is a curve in space where light exists on one side and not the other. The Hubble distance barrier is not constant, it continues to move further outward. The relative Velocity of space increases as space expands constantly. Where light occurs on one side of the Hubble distance, the laws of physics take place. On the other side the laws do not take place. Once light passes the Hubble distance it now moves faster than the speed of light. Thus if light can not be seen or subject to physics, it can not be measured. This may be why Einstein said nothing can move faster than the speed of light. If the Hubble distance is not constant, than if the barrier moves behind the Galaxy that is already going faster than the speed of light it would now be behind the Hubble distance and subject to the laws of physics and Einstein's concept. Would it not be Galactic chaos? The force on the Galaxy going from faster than to slower than the speed of light would be tremendous. An example supporting my hypotheses is a toy top. As it spins it gains speed,as you continue to spin, it will gain enough momentum to move. If a force comes in contact with the spinning object it causes a negative reaction in the tops movements. Thus the object becomes unbalanced and unpredictable. I believe, the same effect should happen to Galaxies. Why does this not occur.
-Seeruk

Don't confuse galaxy velocity with expansion of space. They are not the same. Space can expand faster than the speed of light and doesn't violate relativity. Nothing is moving, just space is expanding.
 
  • #11
Symbreak said:
'Space-time expansion' is a dubious concept. How do we know 'space' is expanding without matter?

How about examining the characteristics of the Cosmic Microwave Background?

thus, the 'expansion of the universe' is infered from the motions of matter.

Since we can't directly measure the proper motion of distant objects, the expansion is inferred from things like the redshifting of light from those objects.

So saying 'it is space which expands' is not entirely correct, since space (or time) cannot exist of itself.

So you're saying spacetime doesn't exist and it's all just an illusion based on our measurements of matter? Sounds like you'll need to replace GR.
 
  • #12
How can you say "The Hubble distance is a curve in space where light exists on one side and not the other." and then argue that light moves "faster than the speed of light" on one side of the Hubble distance and "at the speed of light" on the other? You just said there was NO light on the other side of the Hubble distance to move at all!
 
  • #13
selfAdjoint said:
(Sigh) We should have a FAQ on this. How many times has this question been asked.

The galaxies are not moving through space away from us, the space between us and them is expanding. This is not a velocity and it can happen so fast that the distance between us and the galaxies increases faster than light, but nothing is moving faster than light.
This is paraded around as if it were indisputable fact. I always keep this subject open for discussion, because of the (fact) that expansion of space is not a slam dunk. The possibility that no galaxy recedes from us past the speed of light is most definitely still a possibility. I would consider myself remiss to not consider it as a potential. We could easily be wrong for hundreds of years taking on this sort of practice of perhaps the blind leading the blind.
 
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  • #14
Symbreak said:
So saying 'it is space which expands' is not entirely correct, since space (or time) cannot exist of itself.
The idea of space, however, is suggested by certain primitive experiences. Suppose that a box has been constructed. Objects can be arranged in a certain way inside the box, so that it becomes full. The possibility of such arrangements is a property of the material object "box," something that is given with the box, the "space enclosed" by the box. This is something which is different for different boxes, something that is thought quite naturally at being independent of whether or not, at any moment, there are any objects at all in the box. When there are no objects in the box, its space appears to be "empty."

So far, our concept of space has been associated with the box. It turns out, however, that the storage possibilities that make up this box-space are independent of the thickness of the walls of the box. Cannot this thickness be reduced to zero, without the "space" being lost as a result? The naturalness of such a limiting process is obvious, and now there remains for our thought the space without the box, a self-evident thing, yet it appears to be so unreal if we forget the origin of this concept.
- Einstein, Relativity: The Special and General Theory, Appendix 5: Relativity and the Problem of Space
 
  • #15
Pi_314B said:
This is paraded around as if it were indisputable fact. I always keep this subject open for discussion, because of the (fact) that expansion of space is not a slam dunk. The possibility that no galaxy recedes from us past the speed of light is most definitely still a possibility. I would consider myself remiss to not consider it as a potential. We could easily be wrong for hundreds of years taking on this sort of practice of perhaps the blind leading the blind.
Darn, Pi! you should be be prepared to be treated like the village idiot for even suggesting such a thing around here. The mere suggestion that the Hubble relationship (reshift=distance) is not proof of the expansion of the universe can earn you insults and dismissal in these parts, IF your threads are not summarily shut down. Edwin Hubble would probably be shut down here repeatedly, since he was uncomfortable with the interpretation that the redshift=distance relationship must be interpreted as evidence of universal expansion.

If "empty" space is a transmissive medium, and light can lose energy by crossing it, we should expect that the redshift=distance relationship will give us a pretty good approximation of the density of "empty" space that light traverses between any distant source and our receptors. This is all well and good if you believe in classical optics, but the GR notion that the speed of light in a "vacuum" is invariable is a little too firmly entrenched in the minds of the faithful to allow reasonable consideration of the concept that light may be redshifted by interaction with the space that it traverses.

I hope you're ready for the ride. Good luck!
 
  • #16
εllipse said:
- Einstein, Relativity: The Special and General Theory, Appendix 5: Relativity and the Problem of Space
Thank you for that quote! Epistemology was not a mere mental exercise for Einstein. He was quite willing to consider the properties of space whether it was fully inhabited by sensible matter or devoid of it.
 
  • #17
Hubble was resistant to the concept of redshift = distance, and Einstein was resistant to the concepts of quantum physics. Both men would probably reassess their position if presented with the body evidence since accumulated. That does not diminish their achievements, nor do their achievements diminish the findings of those who stood upon their shoulders. In fact, I suspect they would be quite proud of the fruit their efforts inspired.
 
  • #18
Chronos said:
Hubble was resistant to the concept of redshift = distance
That is not accurate, and I know you understand the distinction, but to clarify: Hubble established that the distances to objects of similar types can be estimated by comparing their redshifts. More distant objects have higher redshifts. Hubble was resistant to the concept that the redshift was due to cosmological expansion. He would probably also be very reluctant to blindly assign cosmological distances on the basis of redshift alone regardless of the type of body under examination. Remember that he was very carefully building the redshift/distance relationship using standard candles, and when standard candles became unavailable at greater distances, other considerations like galaxy morphology became more important in making the extrapolations. He and his contemporaries were observational astromoners who made observations and measurements. Hubble thought that the theoreticians who took his redshift/distance relationship and built an entirely new cosmology on the assumption that redshift=expansion were premature. To Hubble, the causes of cosmological redshift remained an open question.

If one regards space as a transmissive medium (classical optics) it is a trivial matter to explain the redshift/distance relationship in a Steady-State Universe, without resorting to the concept that all space-time is expanding.
 
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  • #19
turbo-1 said:
Darn, Pi! you should be be prepared to be treated like the village idiot for even suggesting such a thing around here. The mere suggestion that the Hubble relationship (reshift=distance) is not proof of the expansion of the universe can earn you insults and dismissal in these parts, IF your threads are not summarily shut down. Edwin Hubble would probably be shut down here repeatedly, since he was uncomfortable with the interpretation that the redshift=distance relationship must be interpreted as evidence of universal expansion.

If "empty" space is a transmissive medium, and light can lose energy by crossing it, we should expect that the redshift=distance relationship will give us a pretty good approximation of the density of "empty" space that light traverses between any distant source and our receptors. This is all well and good if you believe in classical optics, but the GR notion that the speed of light in a "vacuum" is invariable is a little too firmly entrenched in the minds of the faithful to allow reasonable consideration of the concept that light may be redshifted by interaction with the space that it traverses.

I hope you're ready for the ride. Good luck!
I didn't say the expansion of space is wrong. I'm saying it could be, and as a result all possibilities are on the table. To offer the expansion of space as the only possibility with no wiggle room, does a diservice to the very nature of science.

Now there is probably some expectation that I am to lead us all to the promise land for making these statements. I've got news - It won't happen. I am just making a point. The theory that space is expanding is not etched in stone. I repeat - The theory that of space expansion is (not) etched in stone. It is the leading candidate and nothing more.
 
  • #20
Chronos said:
Hubble was resistant to the concept of redshift = distance, and Einstein was resistant to the concepts of quantum physics. Both men would probably reassess their position if presented with the body evidence since accumulated. That does not diminish their achievements, nor do their achievements diminish the findings of those who stood upon their shoulders. In fact, I suspect they would be quite proud of the fruit their efforts inspired.
I whole heartedly agree with you, If they only knew how much they are revered in the science world today and how much they have contributed it, they would be very proud, heck I'm very proud of them.
 
  • #21
Pi_314B said:
I didn't say the expansion of space is wrong. I'm saying it could be, and as a result all possibilities are on the table. To offer the expansion of space as the only possibility with no wiggle room, does a diservice to the very nature of science.

Now there is probably some expectation that I am to lead us all to the promise land for making these statements. I've got news - It won't happen. I am just making a point. The theory that space is expanding is not etched in stone. I repeat - The theory that of space expansion is (not) etched in stone. It is the leading candidate and nothing more.
You are absolutely correct.

The BB model has over 40 years of work from countless physicists invested in it, though, and some folks consider it akin to heresy to question its basic assumption - that cosmological redshift is due to the expansion of the whole Universe. The more radical extension - that all objects, regardless of their types, are at the cosmological distances implied by their redshifts - is also vigorously defended, although I think Hubble would have been loathe to make that assumption, as well.
 
  • #22
Pi_314B said:
Now there is probably some expectation that I am to lead us all to the promise land for making these statements. I've got news - It won't happen. I am just making a point. The theory that space is expanding is not etched in stone. I repeat - The theory that of space expansion is (not) etched in stone. It is the leading candidate and nothing more.

So would you say the theory of the Earth going around the sun is just the "leading candidate"? The evidence is overwhelmingly in favor of the expansion of space and the community has not seriously considered a non-expanding universe for a very long time. Emphasizing that very tiny bit of uncertainty would seem to me counter-productive, especially since the general public seems less convinced about it than the people who actually know what they're talking about. Perhaps you should drop by the relativity and biology forums to emphasize the miniscule bit of uncertainty surrounding the theory of relativity or evolution. That would help, since [sarcasm]we don't get enough of that attitude from the crackpots[/sarcasm].
 
  • #23
No one is saying that scientific theories are set in stone...of course they are open to modification or even replacement. But as Chronos and SpaceTiger noted, there is a significant weight of evidence supporting the mainstream model and it will take some extraordinary new evidence to cause any dramatic shifts in the model.
 
  • #24
The evidence is overwhelmingly in favor of the expansion of space
I would consider this to be a false statement. The evidence is anlogous to going to a folder called expanding space, then to a sub folder, then to a file, then to a page in the file, wherein lies the evidence, while the theory of the Earth going round the Sun has it's evidence located in the folder call Earth round the Sun.
 
  • #25
Pi_314B said:
I would consider this to be a false statement. The evidence is anlogous to going to a folder called expanding space, then to a sub folder, then to a file, then to a page in the file, wherein lies the evidence, while the theory of the Earth going round the Sun has it's evidence located in the folder call Earth round the Sun.
:confused:
 
  • #26
No one is saying that scientific theories are set in stone
The theory regarding expanding space is in most every case passed off as absolute undeniable fact, stated like as if we know exactly what space is. If there is direct observational evidence as to what space is, and exactly how it is that space expands...I'd sure like to hear and see it.
 
  • #27
Pi_314B said:
I would consider this to be a false statement. The evidence is anlogous to going to a folder called expanding space, then to a sub folder, then to a file, then to a page in the file, wherein lies the evidence, while the theory of the Earth going round the Sun has it's evidence located in the folder call Earth round the Sun.

That's not a particularly good analogy, since our level of confidence in a theory depends more on the relative quality of the observations than on the total number of them. If one is going only by the number of different kinds of observations, then the expanding universe likely beats out the sun-centered solar system, despite the latter clearly being more certain. I'm curious, though, what do you think the evidence for the expanding universe is? If it's a "file" worth of information, surely that wouldn't be a tall order.
 
  • #28
relative observations?

I would like to see it too Pi_314B. Like a black hole time discrepancy, is it not relative to the observer. For those who believe in the expansion theory, which I do, you would not feel space expanding because your experiencing it from a single point within space. The closer an object is to your observable field the less of an expansion occurs. Thank all of you who have posted so far. Although I have not read all of the posts due to illness, I have been pondering this question for quite some time.
 
  • #29
Pi_314B said:
The theory regarding expanding space is in most every case passed off as absolute undeniable fact, stated like as if we know exactly what space is. If there is direct observational evidence as to what space is, and exactly how it is that space expands...I'd sure like to hear and see it.

Of course, it depends on what you call direct. In the past 20 years, many galaxies have been discovered with recession speeds (relative to us) exceeding c. If you accept general relativity, then the explanation of this would be an expanding universe will accelerating expansion. The CBMR is also considered direct evidence of the expansion of the universe, although it is not proof it is accelerating.

Nothing we know is absolute. So whatever standard you are holding your breath for, don't expect everyone else to go along with you. Newton was not "wrong" just because he didn't have the facts we have today. When new knowledge is gained, we will adjust for it. No one is trying to put one over on anyone.
 

1. Why do galaxies recede faster than light?

This phenomenon is known as the "metric expansion of space" and is a consequence of the universe's expansion. As the space between galaxies grows, it causes them to move away from each other at faster rates.

2. Does this mean that galaxies are actually moving faster than the speed of light?

No, galaxies themselves are not moving faster than the speed of light. The expansion of space is a fundamental property of the universe and is not constrained by the speed of light.

3. How can we observe galaxies that are receding faster than light?

The light from these galaxies has been traveling for billions of years to reach us, and during that time, the universe has expanded. This means that the galaxies were not receding faster than light when the light was emitted, but the expansion of space has caused them to appear that way to us now.

4. Is there any limit to how fast galaxies can recede?

The expansion of the universe is currently accelerating, but there is no known limit to how fast galaxies can recede. It is possible that the expansion could continue to accelerate, causing galaxies to recede at even faster rates in the future.

5. How does the expansion of space affect the distance between galaxies?

The expansion of space causes the distance between galaxies to increase over time. The farther apart galaxies are, the faster they will be moving away from each other due to the expansion of space.

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