Expansion of the universe and Einstein

originally posted by: HellaKitty
Einstein's E = mc2 predicts nothing that has mass can travel faster than the speed of light

The universe is/contains mass, so how come the equation does not count in the case of the expansion of the universe.

Either Einstein is wrong, or there's something I overlooked, anyone knows how this is possible?

Einstein's equations said it would take infinite energy for an object with mass to reach the speed of light traveling though local space. The expansion of the universe does not involve mass traveling through local space. You seem to have overlooked this answer which is the simplest analogy answering your question:

originally posted by: wildespace
It's the space itself that expands. There's no rules against that. The best example to illustrate that is a rising piece of dough with raisins in it. The raisins don't actually move through the dough, but the expanding dough makes the raisins move away from each other.

So to re-phrase this analogy in terms of Einstein's limits, the raisins can't move through the dough beyond a certain speed (galaxies can't move locally faster than light). But Einstein's math allows the dough to expand faster than the raisins can move through it as long as the distances are great enough to not be local, which is the case in the expanding universe.

originally posted by: HellaKitty
I have seen some reactions saying everything moves away, this is not true.
Andromeda is moving towards the Milky way which indicates there's holes in the theory (yes, I know gravitational forces play a part in this)

That's not a hole in the theory, that's a hole in your understanding of the model which doesn't kick in until the distances are greater than 10 megaparsecs, and you apparently already know why, so I don't know how you can call that a hole in the theory. Andromeda is much closer than that.

originally posted by: chr0naut

originally posted by: wildespace
a reply to: wildespace

Relative velocity (and the resulting redshift, as well as time dilation) is there. I don't know why you assume that's not part of the mainstream model.

Redshift is sub-luminal.

I will repeat that I am NOT denying the metric expansion of the universe. I am pointing out that the reasoning that 'explains' superluminality is invalid.

Relative velocity still doesn't mean the objects are accelerated through space like a rocket accelerates.

However, the relative movements of objects in the scenario are not a special case somehow outside of Einstein's relativity. We have no theoretical or mathematical basis to describe how space expands metrically creating distance between the objects without the relative motion of the objects. ... and C is still invariant!

The red# increase with distance is a direct observation. The "tired light" model was disproved a long time ago. That leaves the actual expansion of space. Plenty of strong observational evidence has been found to support it: en.wikipedia.org...

The redshift is found in all galaxies outside our Local Group, not just quasars.

Just because you don't understand it, doesn't mean it's a myth.

Again, I am not disagreeing with the metric expansion of space-time at sub-light speeds.

I am disagreeing with it as an explanation of the superluminal expansion of the universe.

The idea that beyond the Hubble radius objects can move apart faster than the speed of light is a fudge to fit the data. There is no theory to explain how and why this should be the case.

originally posted by: chr0naut
Redshift is sub-luminal.

I don't know what you mean by that. Light travels through the vacuum at the speed of light, whether it's red shifted, or blue-shifted, or not shifted at all. It would have to be traveling through something other than a vacuum to be subluminal.

However, the relative movements of objects in the scenario are not a special case somehow outside of Einstein's relativity. We have no theoretical or mathematical basis to describe how space expands metrically creating distance between the objects without the relative motion of the objects. ... and C is still invariant!

You could try reading this paper. It provides the mathematical basis for describing the expansion.

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard Lambda-CDM cosmology we point out confusions regarding the particle horizon, the event horizon, the ``observable universe'' and the Hubble sphere (distance at which recession velocity = c). We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests. Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts. We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23 sigma.

FYI looks like you got the infamous "double post", you may want to delete one of them.

originally posted by: Arbitrageur

originally posted by: chr0naut
Redshift is sub-luminal.

I don't know what you mean by that. Light travels through the vacuum at the speed of light, whether it's red shifted, or blue-shifted, or not shifted at all. It would have to be traveling through something other than a vacuum to be subluminal.

If an object emitting photons were moving away from us faster than the speed of light, the photons would never reach us because they can only travel at the speed of light. Therefore, for us to observe a downward frequency shift carried by those photons, the relativistic speed between observer and object would have to be less than C, or sub-luminal.

However, the relative movements of objects in the scenario are not a special case somehow outside of Einstein's relativity. We have no theoretical or mathematical basis to describe how space expands metrically creating distance between the objects without the relative motion of the objects. ... and C is still invariant!

You could try reading this paper. It provides the mathematical basis for describing the expansion.

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard Lambda-CDM cosmology we point out confusions regarding the particle horizon, the event horizon, the ``observable universe'' and the Hubble sphere (distance at which recession velocity = c). We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests. Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts. We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23 sigma.

I think the technical nature of the linked document itself can lead to confusion. They are explicitly talking about observational characteristics of expansion, not the instantaneous values of the 'now'.

The passage of light over vast distances takes time. In that time, a sub-luminal light source, that has emitted the light billions of years ago, is now (instantaneously) moving faster than light away from us as determined by Hubble expansion. Billions of years ago it wasn't, now it is.

This is the difference between the Hubble sphere and the light event horizon. The Hubble sphere can show us observational information that is now outside of the light event horizon.

FYI looks like you got the infamous "double post", you may want to delete one of them.

Thanks, I think I might have actually hit the 'quote' icon rather than the 'edit' one without noticing, so mea culpa.

a reply to: chr0naut

If an object emitting photons were moving away from us faster than the speed of light, the photons would never reach us because they can only travel at the speed of light. Therefore, for us to observe a downward frequency shift carried by those photons, the relativistic speed between observer and object would have to be less than C, or sub-luminal.

This from a hardcopy version of "Einstein's Telescope" , (Evalyn Gates, W.W.Norton and Company, New York, 2009, ISBN 978-0-393-33801-0) Pages 281 and 282, Note 8 for chapter 7. (Any typo's are my fault, I don't have a eBook to cut and paste.)

... The measured redshift is due to a combination of the intrinsic velocity of the galaxy (how fast it's moving around within the cluster) and the recession velocity due to the cosmic expansion. For galaxies well oustside our local area, the redshift is due almost entirely to the expansion of the Universe. Galaxies in a cluster 1 billion light-years away will be zipping around within the cluster at speeds on the order of 1 million miles per hour, while the entire cluster is expanding away from us at a speed of almost 50 million miles per hour. Thus, all the cluster galaxies, regardless of how they are moving within the cluster, will have close to the same redshift...
To be precise, it is the expansion of space itself that results in the redshifting of distant galaxies - galaxies are not moving through space away from us, but rather with space as it expands...
The light travel time distance is essentially the distance light would have traveled in the time since it was emitted if the Universe were not expanding. This is not the distance between us and the source of light today, especially at large redshifts. The object that emitted the light continues to expand away from us so that today it is no longer where it was when the light left it...

Thus, the light we see today from these very distant galaxies (or clusters) are from when they wer much closer to us and since the universe expansion is accelerating they are NOW moving away from us more quickly. It is possible that they are NOW moving away from us at faster than light. Which means that at some time in the future the light from those galaxies will disappear from our view after the last light emitted before they hit the Hubble Boundary reaches us.

If we are observing a galaxy that is a billion light years away, the light has taken a billion years to get here and the entire universe has in the meantime undergone a billion years worth of accelerating expansion. The galaxy is much farther away and the local space it is in is moving much faster.

originally posted by: rnaa
a reply to: chr0naut

If an object emitting photons were moving away from us faster than the speed of light, the photons would never reach us because they can only travel at the speed of light. Therefore, for us to observe a downward frequency shift carried by those photons, the relativistic speed between observer and object would have to be less than C, or sub-luminal.

This from a hardcopy version of "Einstein's Telescope" , (Evalyn Gates, W.W.Norton and Company, New York, 2009, ISBN 978-0-393-33801-0) Pages 281 and 282, Note 8 for chapter 7. (Any typo's are my fault, I don't have a eBook to cut and paste.)

... The measured redshift is due to a combination of the intrinsic velocity of the galaxy (how fast it's moving around within the cluster) and the recession velocity due to the cosmic expansion. For galaxies well oustside our local area, the redshift is due almost entirely to the expansion of the Universe. Galaxies in a cluster 1 billion light-years away will be zipping around within the cluster at speeds on the order of 1 million miles per hour, while the entire cluster is expanding away from us at a speed of almost 50 million miles per hour. Thus, all the cluster galaxies, regardless of how they are moving within the cluster, will have close to the same redshift...
To be precise, it is the expansion of space itself that results in the redshifting of distant galaxies - galaxies are not moving through space away from us, but rather with space as it expands...
The light travel time distance is essentially the distance light would have traveled in the time since it was emitted if the Universe were not expanding. This is not the distance between us and the source of light today, especially at large redshifts. The object that emitted the light continues to expand away from us so that today it is no longer where it was when the light left it...

Thus, the light we see today from these very distant galaxies (or clusters) are from when they wer much closer to us and since the universe expansion is accelerating they are NOW moving away from us more quickly. It is possible that they are NOW moving away from us at faster than light. Which means that at some time in the future the light from those galaxies will disappear from our view after the last light emitted before they hit the Hubble Boundary reaches us.

If we are observing a galaxy that is a billion light years away, the light has taken a billion years to get here and the entire universe has in the meantime undergone a billion years worth of accelerating expansion. The galaxy is much farther away and the local space it is in is moving much faster.

Precisely.

But the acceleration due to expansion cannot actually exceed the speed of light from our theoretical observational frame due to Lorentz contraction of spacetime. I say 'theoretical observational frame' because we cannot actually observe the distant object (at some time in the future) because its photons will never reach us.

originally posted by: chr0naut
But the acceleration due to expansion cannot actually exceed the speed of light from our theoretical observational frame due to Lorentz contraction of spacetime. I say 'theoretical observational frame' because we cannot actually observe the distant object (at some time in the future) because its photons will never reach us.

The paper I posted says otherwise so I don't think you understood it if you read it, and I don't know why you bring up Lorentz contraction of spacetime in a discussion of photons, that applies to things like "rods", not photons.

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests.

originally posted by: chr0naut
I think the technical nature of the linked document itself can lead to confusion. They are explicitly talking about observational characteristics of expansion, not the instantaneous values of the 'now'.

Again I don't think you understand the paper. It calculates and provides spacetime diagrams which indeed show instantaneous values for "now" in addition to past positions for the history of the universe.

a reply to: chr0naut

You are still missing the concept. Relativity is only applicable to matter in space-time. It is not applicable to space-time itself.

A matter in space-time cannot move (relative to some reference framework) faster than light.

Space-time is not 'matter' and it is not 'in' space-time. Space-time can expand faster than light.

Matter in a local area (I believe the mathematics says a local area is less than about 10 parsecs, but I could be wrong) will be 'carried along with' the expansion of space-time and will therefore be getting farther away from other bits of local area.

Matter in local areas that is being carried away from matter in other local areas due to space-time expansion does not violate the FTL speed limit because there is no appropriate frame of reference. It is not moving through space-time, it is being carried along by space-time.

originally posted by: chr0naut

originally posted by: rnaa
a reply to: chr0naut

If an object emitting photons were moving away from us faster than the speed of light, the photons would never reach us because they can only travel at the speed of light. Therefore, for us to observe a downward frequency shift carried by those photons, the relativistic speed between observer and object would have to be less than C, or sub-luminal.

This from a hardcopy version of "Einstein's Telescope" , (Evalyn Gates, W.W.Norton and Company, New York, 2009, ISBN 978-0-393-33801-0) Pages 281 and 282, Note 8 for chapter 7. (Any typo's are my fault, I don't have a eBook to cut and paste.)

... The measured redshift is due to a combination of the intrinsic velocity of the galaxy (how fast it's moving around within the cluster) and the recession velocity due to the cosmic expansion. For galaxies well oustside our local area, the redshift is due almost entirely to the expansion of the Universe. Galaxies in a cluster 1 billion light-years away will be zipping around within the cluster at speeds on the order of 1 million miles per hour, while the entire cluster is expanding away from us at a speed of almost 50 million miles per hour. Thus, all the cluster galaxies, regardless of how they are moving within the cluster, will have close to the same redshift...
To be precise, it is the expansion of space itself that results in the redshifting of distant galaxies - galaxies are not moving through space away from us, but rather with space as it expands...
The light travel time distance is essentially the distance light would have traveled in the time since it was emitted if the Universe were not expanding. This is not the distance between us and the source of light today, especially at large redshifts. The object that emitted the light continues to expand away from us so that today it is no longer where it was when the light left it...

Thus, the light we see today from these very distant galaxies (or clusters) are from when they wer much closer to us and since the universe expansion is accelerating they are NOW moving away from us more quickly. It is possible that they are NOW moving away from us at faster than light. Which means that at some time in the future the light from those galaxies will disappear from our view after the last light emitted before they hit the Hubble Boundary reaches us.

If we are observing a galaxy that is a billion light years away, the light has taken a billion years to get here and the entire universe has in the meantime undergone a billion years worth of accelerating expansion. The galaxy is much farther away and the local space it is in is moving much faster.

Precisely.

But the acceleration due to expansion cannot actually exceed the speed of light from our theoretical observational frame due to Lorentz contraction of spacetime. I say 'theoretical observational frame' because we cannot actually observe the distant object (at some time in the future) because its photons will never reach us.

"Cannot be observed" doesn't equal "cannot actually exceed". We can't see those galaxies moving away at or faster than c, true, but we know they must be, due to how the visible galaxies are redshifted, and how the rest of space is black rather than filled with glow of the infinite (or nearly-infinite) number of galaxies.

Take a look at one of those Ultra-Deep-Field Hubble images. The most distant galaxies visible there are very visibly redshifted. Even more distant ones are detectable in infrared and radio waves, beyond which they are too redshifted to be detectable.

originally posted by: rnaa
a reply to: chr0naut

You are still missing the concept. Relativity is only applicable to matter in space-time. It is not applicable to space-time itself.

A matter in space-time cannot move (relative to some reference framework) faster than light.

Space-time is not 'matter' and it is not 'in' space-time. Space-time can expand faster than light.

Matter in a local area (I believe the mathematics says a local area is less than about 10 parsecs, but I could be wrong) will be 'carried along with' the expansion of space-time and will therefore be getting farther away from other bits of local area.

Matter in local areas that is being carried away from matter in other local areas due to space-time expansion does not violate the FTL speed limit because there is no appropriate frame of reference. It is not moving through space-time, it is being carried along by space-time.

Perhaps you could consider this: If spacetime is expanding, it is either that more spacetime that is coming into existence or it is that the spacetime which is there is being stretched out.

In the case of more spacetime coming into existence, we know it has certain values such as its permittivity, its bubbling field of transient vparticles and its vacuum field strength. These are tangible and measurable things. If spacetime is coming into existence, how and why? Where is it coming from? How do we explain it?

If spacetime is merely being stretched to expand, what provides the negative energy sufficient to stretch it to such an incredible degree as to comply with the Hubble rate of expansion?

originally posted by: wildespace

originally posted by: chr0naut

originally posted by: rnaa
a reply to: chr0naut

If an object emitting photons were moving away from us faster than the speed of light, the photons would never reach us because they can only travel at the speed of light. Therefore, for us to observe a downward frequency shift carried by those photons, the relativistic speed between observer and object would have to be less than C, or sub-luminal.

This from a hardcopy version of "Einstein's Telescope" , (Evalyn Gates, W.W.Norton and Company, New York, 2009, ISBN 978-0-393-33801-0) Pages 281 and 282, Note 8 for chapter 7. (Any typo's are my fault, I don't have a eBook to cut and paste.)

... The measured redshift is due to a combination of the intrinsic velocity of the galaxy (how fast it's moving around within the cluster) and the recession velocity due to the cosmic expansion. For galaxies well oustside our local area, the redshift is due almost entirely to the expansion of the Universe. Galaxies in a cluster 1 billion light-years away will be zipping around within the cluster at speeds on the order of 1 million miles per hour, while the entire cluster is expanding away from us at a speed of almost 50 million miles per hour. Thus, all the cluster galaxies, regardless of how they are moving within the cluster, will have close to the same redshift...
To be precise, it is the expansion of space itself that results in the redshifting of distant galaxies - galaxies are not moving through space away from us, but rather with space as it expands...
The light travel time distance is essentially the distance light would have traveled in the time since it was emitted if the Universe were not expanding. This is not the distance between us and the source of light today, especially at large redshifts. The object that emitted the light continues to expand away from us so that today it is no longer where it was when the light left it...

Thus, the light we see today from these very distant galaxies (or clusters) are from when they wer much closer to us and since the universe expansion is accelerating they are NOW moving away from us more quickly. It is possible that they are NOW moving away from us at faster than light. Which means that at some time in the future the light from those galaxies will disappear from our view after the last light emitted before they hit the Hubble Boundary reaches us.

If we are observing a galaxy that is a billion light years away, the light has taken a billion years to get here and the entire universe has in the meantime undergone a billion years worth of accelerating expansion. The galaxy is much farther away and the local space it is in is moving much faster.

Precisely.

But the acceleration due to expansion cannot actually exceed the speed of light from our theoretical observational frame due to Lorentz contraction of spacetime. I say 'theoretical observational frame' because we cannot actually observe the distant object (at some time in the future) because its photons will never reach us.

"Cannot be observed" doesn't equal "cannot actually exceed". We can't see those galaxies moving away at or faster than c, true, but we know they must be, due to how the visible galaxies are redshifted, and how the rest of space is black rather than filled with glow of the infinite (or nearly-infinite) number of galaxies.

This doesn't indicate that galaxies are moving away faster than c because before we get to that velocity, we loose visibility (at least on time frames that are less than the age of the universe).

We know that spacetime dilates to keep ALL velocities below c from ALL timeframes. This is why c is a constant. If matter tries to move faster than c, spacetime deforms, keeping c constant. If things were able to move faster than c, then c would be a variable, not a constant. The superluminal expansion of the universe is exactly opposite to relativistic movement in many aspects.

The assumption that outside of local inertial reference frames things can exceed c, would disconnect the very nature of what spacetime is. It would mean that distant spacetime is different stuff than local spacetime and that we therefore couldn't trust any of our known physics to actually operate in expected ways for non-local events.

Take a look at one of those Ultra-Deep-Field Hubble images. The most distant galaxies visible there are very visibly redshifted. Even more distant ones are detectable in infrared and radio waves, beyond which they are too redshifted to be detectable.

Some distant objects, known as blue outliers, are notably blue shifted. If spactime was isotropic and homogenous, as is suggested, that should be impossible, but we observe them.

a reply to: chr0naut

If spacetime is merely being stretched to expand, what provides the negative energy sufficient to stretch it to such an incredible degree as to comply with the Hubble rate of expansion?

We don't know yet. But until we do we have a nickname to use as a placeholder until we know more.

For the time being we call it 'Dark Energy'.

originally posted by: rnaa
a reply to: chr0naut

If spacetime is merely being stretched to expand, what provides the negative energy sufficient to stretch it to such an incredible degree as to comply with the Hubble rate of expansion?

We don't know yet. But until we do we have a nickname to use as a placeholder until we know more.

For the time being we call it 'Dark Energy'.

Oh, I see.

When you meet a roadblock in one hypothesis, you can fully fill all the holes with another hypothesis?

So, two (bad?) guesses = truth?

originally posted by: chr0naut

originally posted by: rnaa
a reply to: chr0naut

If spacetime is merely being stretched to expand, what provides the negative energy sufficient to stretch it to such an incredible degree as to comply with the Hubble rate of expansion?

We don't know yet. But until we do we have a nickname to use as a placeholder until we know more.

For the time being we call it 'Dark Energy'.

Oh, I see.

When you meet a roadblock in one hypothesis, you can fully fill all the holes with another hypothesis?

Well, in a way yes. If an hypothesis, after testing, is found to not accurately describe the observed phenomenon it addresses, it is either rejected in favor of another, better hypothesis or corrected and retested. That is, in essence, the scientific method. Do you have a problem with that?

So, two (bad?) guesses = truth?

What guesses are involved here, good or bad?

Dark Energy isn't a guess. It isn't even an hypothesis. Its a reaction to an observation pending an hypothesis.

Observed: the universe is expanding.
Observed: the expansion is accelerating.

Question: what causes the acceleration?
Answer: I dunno, but it must have a crap load of mass/energy and have a rather peculiar set of properties in order to do it.

Question: well what things do we know that have those properties?
Answer: nothing. And we are still finding out what all those weird properties are so we can have some idea about what to look for.

Question: OK then, what are you looking for?
Answer: We don't know enough to answer that question yet. We know it is there because of its influence on the universe. For the time being we are calling it "Dark Energy" but we don't know that it is energy and the "dark" part is there because we can't see it.

It isn't a guess, the expansion of the Universe is observed to be accelerating; there is no guesswork involved. What is causing the acceleration is unknown. We currently call that cause "Dark Energy", but that is not a guess and it is not an hypothesis; it is a nickname for that unknown cause.

originally posted by: Arbitrageur

originally posted by: chr0naut
But the acceleration due to expansion cannot actually exceed the speed of light from our theoretical observational frame due to Lorentz contraction of spacetime. I say 'theoretical observational frame' because we cannot actually observe the distant object (at some time in the future) because its photons will never reach us.

The paper I posted says otherwise so I don't think you understood it if you read it, and I don't know why you bring up Lorentz contraction of spacetime in a discussion of photons, that applies to things like "rods", not photons.

The photons have to travel to reach us, hence their path is 'rod like' and the space-time distance covered dilates relative to the sum velocities between the objects (calculable by Lorentz contraction).

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests.

originally posted by: chr0naut
I think the technical nature of the linked document itself can lead to confusion. They are explicitly talking about observational characteristics of expansion, not the instantaneous values of the 'now'.

Again I don't think you understand the paper. It calculates and provides spacetime diagrams which indeed show instantaneous values for "now" in addition to past positions for the history of the universe.

There are other and later papers that disagree with many aspects of the linked paper. But also:

Martin Rees & Steven Weinberg (1993) state: "...how is it possible for space, which is utterly empty, to expand? How can nothing expand? The answer is: space does not expand. Cosmologists sometimes talk about expanding space, but they should know better".

Feynman Lectures on Gravitation (1962/63), “It makes no sense to worry about the possibility of galaxies receding from us faster than light, whatever that means, since they would never be observable by hypothesis.”

Raine, D. J. 1981, The Isotropic Universe, (Bristol: Adam Hilber Ltd) p. 87, “One might suspect special relativistic effects to be important since some quasars are observed to exhibit redshifts, z, in excess of unity. This is ncompatible with a Newtonian interpretation of the Doppler effect, since one would obtain velocities v=cz in excess of that of light. The special relativistic Doppler formula 1 + z = (c + v)/(c − v) 1/2 always leads to sub-luminal velocities for objects with arbitrarily large red-shifts, and is at least consistent. In fact we shall find that the strict special relativistic interpretation is also inadequate. Nevertheless, at the theoretical edge of the visible Universe we expect at least in
principle to see bodies apparently receding with the speed of light".

originally posted by: chr0naut
If spacetime is merely being stretched to expand, what provides the negative energy sufficient to stretch it to such an incredible degree as to comply with the Hubble rate of expansion?

Vacuum itself provides it, just as it's being stretched. Vacuum isn't like rubber which requires an outside application of energy and wants to come back to its original shape when released. Vacuum drives its own expansion.

a reply to: rnaa

Observed: the universe is expanding.
Observed: the expansion is accelerating.

Again expanding space has not been observed nor measured.

It is the absorption lines in light that have shifted to the red end of the spectrum that have been observed from distant galaxies and Quasars. Some of these objects have higher redshifts than others and this is thought to indicate greater distances and velocities. This is where we get the expanding space theory.

Since we are unable to take in situ measurements of these objects we use the Hubble as a constant to indicate both speed and distance. A problem arises with apparent faster than light velocities as per high redshifts observed.

Question: what causes the acceleration?
Answer: I dunno, but it must have a crap load of mass/energy and have a rather peculiar set of properties in order to do it.

Question: well what things do we know that have those properties?
Answer: nothing. And we are still finding out what all those weird properties are so we can have some idea about what to look for.

Question: OK then, what are you looking for?
Answer: We don't know enough to answer that question yet. We know it is there because of its influence on the universe. For the time being we are calling it "Dark Energy" but we don't know that it is energy and the "dark" part is there because we can't see it.

Or the Hubble is not a constant and the observed redshift is caused by an intrinsic property. There are many other problems with 'H', see Halton Arp.

a reply to: Arbitrageur

The paper I posted says otherwise so I don't think you understood it if you read it,

I read it, thank you for the link, and I failed to understand it. I still do not get how this is not a violation of relativity. I wish you could explain this in terms I could understand. Until then I'll remain skeptical.

Do you think an easier explanation could be a problem with 'H' as a constant. If this were thought of as a problem I feel there are several directions we could go in attempting to disprove this as a constant.

a reply to: Devino

Again expanding space has not been observed nor measured.

Oh... so that's why the discoverers got Nobel Prizes for their work?

Again, from Professor Wikipedia: Accelerating expansion of the universe

The accelerating expansion of the universe is the observation that the universe appears to be expanding at an increasing rate,[1] so that the velocity at which a distant galaxy is receding from the observer is continuously increasing with time.[2]

The accelerated expansion was discovered in 1998, by two independent projects, the Supernova Cosmology Project and the High-Z Supernova Search Team, which both used distant type Ia supernovae as standard candles to measure the acceleration.[3][4][5] The discovery was unexpected, cosmologists at the time expecting that the expansion would be decelerating due to the gravitational attraction of the matter in the universe. Three members of these two groups have subsequently been awarded Nobel Prizes for their discovery.[6] Confirmatory evidence has been found in baryon acoustic oscillations and in analyses of the clustering of galaxies.

Notice that the observation was first made TWENTY YEARS AGO.

Please try to keep up.