Relativity and expansion question

a reply to: Archivalist

Well, relatively either the universe is expanding or everything we use as a comparison is shrinking. This would have to include energy as spacetime has an energy density, which is reducing and raising entropy as it goes.

We can propose methods to explain the expansion of empty space and that matter and energy are being dispersed in it but it is difficult to explain a process by which everything could be shrinking (in absolute terms).

I would suggest that the expansion of spacetime is an artefact of our perception in that we can observe (mathematically) event horizons of various types. If the universe is expanding, even by quite small rates, its outer edges would be expanding away from their opposites superluminally, due to the vastness of space.

In such an expanding universe, event horizons (as a differential between expansion and contraction and limited by c) would be exceptionally unlikely, if not totally impossible.

Even in a static universal topology, event horizons should not be likely.

In a contracting universe, however, event horizons become a mandatory feature.

Therefore, if we can observe the effects of event horizons, the universe must be contracting, which makes our observations of effects such as the Hubble constant to not be what we believe we are seeing (i.e: the Hubble constant based upon assumed redshift may not be due to optical doppler shift).

What it may be telling us is anyone's guess. Suffice to say, we only know that we don't even have a glimmer of an answer. So the future is wide open.

originally posted by: argentus
a reply to: projectvxn

Unless Edwin Hubble's constant is wrong, which is possible, but improbable. An interesting (to me) facet of Hubble's work indicates that nearby galaxies are moving away from ours at a slower rate than those much further away.

Couldn't this also be explained then by simple energy dissipation? Photons of light from more distant sources will dissipate in energy and therefore have a lower wavelength aka redshift. Correct? (Inverse-square law energy dissipation)


Unless there is proof that the redshift for galaxies are all increasing every year, then this would insist they are actively moving further away.

originally posted by: projectvxn
a reply to: odzeandennz
The space in galaxies and local group clusters is not expanding.

Space is expanding everywhere, even at a galactic scale. It is the intrinsic property of space to be expanding.

It's just that local gravitational forces are stronger than that expansion, so the local groups and clusters move in their own way.

However, it's theorised that, since the expansion of the universe is accelerating, eventually the galaxies and all matter in them will stretch themselves out to the point the universe rips itself apart.

originally posted by: wildespace
However, it's theorised that, since the expansion of the universe is accelerating, eventually the galaxies and all matter in them will stretch themselves out to the point the universe rips itself apart.

I think to say that theory is unlikely is an understatement, maybe very unlikely is closer.

Why is a cosmological Big Rip scenario not likely?

phantom energy violates the dominant energy condition (basically, it allows mass-energy to flow faster than light) which is a strong reason to believe that phantom energy does not exist. Which is why the big rip scenario is indeed unlikely.

That theory is not a necessary consequence of the accelerating expansion of the universe. The expansion of the universe can be accelerating without it ending in a big rip, and in fact a "Big Chill or Big Freeze" is the most likely fate based on current data.

a reply to: wildespace

Space is expanding everywhere, even at a galactic scale. It is the intrinsic property of space to be expanding.

Sorry, but observations do not support that position.

a reply to: projectvxn
Maybe it's trying to expand everywhere but on local scales where gravitational (or electromagnetic) interactions dominate, the realized expansion is too small to measure. I once saw a calculation of how much the Earth's orbit should be expanding based on the model for the expansion of the universe. The model resulted in a theoretically predicted result which was too small to accurately measure. So on that basis, the fact that observations don't support it doesn't necessarily mean that it's not happening, it could be happening and matching theoretical predictions which say that it should be too small to measure.

You are correct that observations don't support it, but I think that needs to be put in context so I tried to do that. You could turn that around and say that observations also do not reject the idea, they are inconclusive since they would be consistent with either no expansion or an immeasurably small theoretically predicted expansion.

One example I like to cite is, drop a paper clip. The paper clip accelerates toward the Earth. Theory also says the Earth accelerated toward the paper clip, but you'll never measure that acceleration. That doesn't mean it doesn't happen, it's just too small to measure.

originally posted by: Archivalist

originally posted by: projectvxn
a reply to: Archivalist

Space is not equally expanding everywhere.

As I said and referenced, dark energy, which is what is causing the expansion and acceleration of that expansion, is overcome by local group clusters and has no effect within galacies at all. The galaxy has been around since the beginning and it is still a cohesive structure.

Look up IC 1101. It is the most massive galaxy ever discovered. 1 million ly across, with over a trillion stars worth of mass. It is among the most ancient objects in the known universe. If it were going to fly apart due to the accelerating expansion of space, it would not be visible to us at all now because the structure would have fallen apart.

So, dark energy...

Dark energy is the coefficient we add in to our formulas, as a way to explain the fact that our expansion model doesn't seem to work the same, when looking at clusters of matter?

So... Why do we assume dark energy is a thing, and that our model of expansion is correct?
Rather than assuming our expansion model is incorrect?

The universe is expanding due to the pushing effect of quantum fluctuations in zero-point energy field. This effect has been observed in the lab, and is also caled the Casimir effect.

a reply to: Arbitrageur

If it is too small to measure, it is effectively not happening. There is no expansion. We have been in roughly this orbital position for billions of years. The rate of expansion being as fast as it is (and continues to get) would have us lightyears from our sun by now.

No measurable change, means no change effectively. Which means that it isn't happening at these scales. Gravity is too strong.

originally posted by: Arbitrageur
a reply to: projectvxn
Maybe it's trying to expand everywhere but on local scales where gravitational (or electromagnetic) interactions dominate, the realized expansion is too small to measure.

Exactly. The expansion is happening at these scales, but it's incredibly small. The larger the scale you're looking at, the stronger the expansion.

Like I said, expansion is the intrinsinc property of space itself, regardless of what the galaxies are doing.

a reply to: wildespace

Like I said, expansion is the intrinsinc property of space itself, regardless of what the galaxies are doing.

There is no evidence that the accelerated expansion is a property of space.

Not that there isn't an argument for it. We don't know what is causing the expansion of space to accelerate. That requires a form of energy. This energy is NOT strong enough at the local group or at the galactic scale to overcome gravity. Expansion in these regions is NOT happening. Observations are consistent with this view.

a reply to: Archivalist



deep space telescopes have identified many Quasars and other Exotic Stars which are 'birthing' all types of young and already developed Stars... these are the Stars which were once theorized as 'White Holes' where matter burst forth into the Vacuum of Space


And as a result of those freshly 'born' Stars popping into Nebulas that form into new Galaxies... the Fabric of Time Space is thus stretched at the speed of 'Inflation' rather than stretching at the slower pace of: The Speed-of-Light



i'm paraphrasing here, about stuff I read in the past few months, courtesy of Diehold Foundation & Dr. Vogt

a reply to: projectvxn
I don't think there is any fundamental difference between what you're saying and what Wildespace said, my point was that observations don't rule it out if theory predicts the amount will be too small to measure on small local scales. If you want to say it's effectively not happening because it can't be measured, I can't argue with that, I also can't argue with the premise that it could be happening at theoretically predicted levels (which are too small to measure). That's just two different ways of looking at the same thing and I don't have any problem with either approach.

originally posted by: projectvxn
a reply to: wildespace

Like I said, expansion is the intrinsinc property of space itself, regardless of what the galaxies are doing.

We don't know what is causing the expansion of space to accelerate. That requires a form of energy.

Yes, the energy of vacuum.

Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal in magnitude to ρ. Thus, the total is ρ + 3p = ρ − 3ρ = −2ρ, a negative value. If indeed the vacuum ground state has non-zero energy, the calculation implies a repulsive gravitational field, giving rise to acceleration of the expansion of the universe.

a reply to: wildespace

No we don't.

You need to read that wiki page more thoroughly.

a reply to: Arbitrageur

If theory and observation don't match then the theory must change. Not the other way around.

originally posted by: Archivalist
Can it be said with confidence that the inverse of universal expansion is also true?

Are all particles and waves shrinking, relative to the space that is expanding?

If we know this is, or is not the case, how do we know that?

Can this even be measured?

Only way I know of mrasiring the expansion or contraction of space is to use temporal proxies. You need monopolies for that, hope you know how to make them :-)

Cheers - Dave

originally posted by: projectvxn
a reply to: Arbitrageur

If theory and observation don't match then the theory must change.

Where do they not match?

a reply to: Arbitrageur

No observational data of space expanding in our local space.

originally posted by: projectvxn
a reply to: Arbitrageur

No observational data of space expanding in our local space.

Since theory predicts the expansion would be immeasurably small on local scales, I think that's a match between theory and observation, which as I said means the observation is inconclusive about the theory. There is no reason to change the theory in this case, just like there's no reason to reject the theory of gravity just because you can't measure how much the earth accelerates toward a paper clip when you drop the paper clip. Theory says that will happen too but you just can't measure it.

originally posted by: projectvxn
a reply to: Arbitrageur

If it is too small to measure, it is effectively not happening. There is no expansion. We have been in roughly this orbital position for billions of years. The rate of expansion being as fast as it is (and continues to get) would have us lightyears from our sun by now.

No measurable change, means no change effectively. Which means that it isn't happening at these scales. Gravity is too strong.

Is there some diode like, drop-off?

Is there a known point, where acceleration of matter towards other matter will fully cancel out all expansion effects, with a one-way street? How would we even indicate that? The two mass values and the acceleration rate?

Rather than the acceleration being inhibited by the expansion effects?