<p>If you work out the equations of motion for the gravitational free-fall collapse of a clouds of particles (or galaxies), you will find that, from the point of view of <em>any</em> of these particles, all other particles appear to be approaching. This is true in both Newtonian theory and general relativity.</p>

<p>The calculation is found in numerous text books and lecture notes, e.g. <a href="http://www.astro.uu.se/~hoefner/astro/teach/apd_files/apd_collapse.pdf" rel="nofollow noreferrer">Susanne Höfner's</a>, but a qualitative argument goes like this:</p>

<p>From your point of view, sitting on one of the particles, a particle farther from the center of the cloud does "feel" a smaller gravitational pull from the central particles. This is, I think, the reason that you think it should accelerate more slowly. However, any particle feels the gravity from <em>all</em> particles that are closer to the center, so the farther you are from the center, the more particles will attract you. On the other hand, the gravity from all particles that are <em>farther</em> away from the center cancels out, so you don't feel those.</p>

<p>This is, in essence, <a href="https://en.wikipedia.org/wiki/Shell_theorem" rel="nofollow noreferrer">Newton's shell theorem</a>, and it turns out to imply that <em>all particles reach the center at the same time</em>. The distance between each particle is getting smaller and smaller, until the cloud collapses into an point after a a time inversely proportional to the square root of the density.</p>

<p>This is exactly opposite to what is observed.</p>

CC BY-SA 4.0
2019-03-20T11:02:51.140Z
2019-03-20T11:02:51.140Z
pela
<p>The basis and most observable metric for how the universe is understood to be expanding at an accelerating rate is the red shift in observable light.  I am assuming it has been thought about or maybe it is just obviously wrong to people with more knowledge, but why can we not say the universe is technically always collapsing on itself under gravity's pull when considering relativity?</p>

<p>We know that space and time are affected by gravity so if we think in relative terms if everything is accelerating at an accelerating rate towards everything else this could explain the red shift (appearance of moving away). Things behind me would be accelerating slower towards the singularity things in front of us would be accelerating faster. Therefore relative to us it would actually look like it is all expanding at an accelerating rate, explaining the red shift.</p>

<p>In this very simplistic thinking, this would work for a universe that expands and contracts or is in a never ending state of contraction, which relative to us could go on infinitely since time and space is all intertwined with gravity.</p>

CC BY-SA 4.0
2019-03-18T19:30:29.673Z
Have you read [Wikipedia's page on the Expansion of the Universe](https://en.wikipedia.org/wiki/Expansion_of_the_universe) ?  Your ideas, as I understand them, directly contradict what is known.  Also understand there is [no center to the universe](https://physics.stackexchange.com/questions/25591/does-the-universe-have-a-center) and hence no concept of "behind" or "in front" as you seem to suggest.
StephenG - Help Ukraine
CC BY-SA 4.0
2019-03-19T10:38:16.737Z
I'm voting to close this question as off-topic because this is about a personal theory with so evidence cited in support of it.
Chappo Hasn't Forgotten
CC BY-SA 4.0
2019-03-19T14:56:50.733Z
Hi new contributor!  Be very cautious with phrases like "it appears to me," as that's a red flag for unsubstantiated wishing/guesswork.  If you are starting from some technical sources, please cite them and explain your derivations.
Carl Witthoft
CC BY-SA 4.0
2019-03-20T04:38:45.357Z
Thanks for responding.  I have read this Wikipedia page.  I'll probably go back and and see if I can further my understanding.  I thought about explaining I knew there was no center, because i was using a very simplistic example of my theory.  Really this would not affect the concept of just everything (including space-time) accelerating towards everything at an accelerating rate.
Scott
CC BY-SA 4.0
2019-03-20T04:59:41.313Z
I agree this is a personal theory and would contradict most known things on the subject as it questions the basis for the understanding that the universe is expanding at an accelerating rate.  My only reference for this theory is General Relativity and red-shift.  I guess a better and simpler way of getting to debunking my wild theory is asking how does GR affect red-shift calculations?  The collapsing of space time could appear as expansion when looking through the lens of a 3 dimensional observer or am I misunderstanding the affects of gravity on space-time and its relationship to light?
Scott
CC BY-SA 4.0
2019-03-20T07:14:53.020Z
*Things behind me would be accelerating slower towards the singularity things in front of us would be accelerating faster.* Which singularity are you talking about?
PM 2Ring
CC BY-SA 4.0
2019-03-20T08:07:27.663Z
That won't fit in a perpendicular line of sight, at least in a flat space.
Alchimista
CC BY-SA 4.0
2019-03-20T08:16:57.567Z
"How does GR affect redshift calculations"? Cosmological redshift *is* a GR effect. Its similarity to a Doppler shift caused by motion is only true for small redshifts.
ProfRob
CC BY-SA 4.0
2019-03-20T10:35:09.503Z
I don't think this question should be closed as a "personal theory". The OP makes clear that probably he's not right, and just want to know where the flaw is".
pela
CC BY-SA 4.0
2019-03-20T10:37:17.100Z
But yeah, you might want to delete the sentence "_here is a theory_" in order not to upset people. You might even want to read up on the difference between theory, hypothesis, and ideas :)
pela
CC BY-SA 4.0
2019-03-21T13:27:24.990Z
Rob - you are saying that we know the GR redshift and it would not account for the quantity we observe in the visible universe?
Scott
CC BY-SA 4.0
2019-03-21T13:32:59.893Z
Pela - Thanks for correcting my scientific grammar. so I have a hypothesis based on possibly misunderstood ideas.
Scott
<gravity><universe><space-time><general-relativity><expansion>
Looking at the Expanding Universe through the lens of relativity
Scott
# Looking at the Expanding Universe through the lens of relativity

(Asked by: username_0 on 2019-03-18)

The basis and most observable metric for how the universe is understood to be expanding at an accelerating rate is the red shift in observable light. I am assuming it has been thought about or maybe it is just obviously wrong to people with more knowledge, but why can we not say the universe is technically always collapsing on itself under gravity's pull when considering relativity?

We know that space and time are affected by gravity so if we think in relative terms if everything is accelerating at an accelerating rate towards everything else this could explain the red shift (appearance of moving away). Things behind me would be accelerating slower towards the singularity things in front of us would be accelerating faster. Therefore relative to us it would actually look like it is all expanding at an accelerating rate, explaining the red shift.

In this very simplistic thinking, this would work for a universe that expands and contracts or is in a never ending state of contraction, which relative to us could go on infinitely since time and space is all intertwined with gravity.

**Tags:** gravity, universe, space-time, general-relativity, expansion
> **Comments:**
> **username_1**: Have you read [Wikipedia's page on the Expansion of the Universe](https://en.wikipedia.org/wiki/Expansion_of_the_universe) ?  Your ideas, as I understand them, directly contradict what is known.  Also understand there is [no center to the universe](https://physics.stackexchange.com/questions/25591/does-the-universe-have-a-center) and hence no concept of "behind" or "in front" as you seem to suggest.  
> **username_2**: I'm voting to close this question as off-topic because this is about a personal theory with so evidence cited in support of it.  
> **username_3**: Hi new contributor!  Be very cautious with phrases like "it appears to me," as that's a red flag for unsubstantiated wishing/guesswork.  If you are starting from some technical sources, please cite them and explain your derivations.  
> **username_0**: Thanks for responding.  I have read this Wikipedia page.  I'll probably go back and and see if I can further my understanding.  I thought about explaining I knew there was no center, because i was using a very simplistic example of my theory.  Really this would not affect the concept of just everything (including space-time) accelerating towards everything at an accelerating rate.  
> **username_0**: I agree this is a personal theory and would contradict most known things on the subject as it questions the basis for the understanding that the universe is expanding at an accelerating rate.  My only reference for this theory is General Relativity and red-shift.  I guess a better and simpler way of getting to debunking my wild theory is asking how does GR affect red-shift calculations?  The collapsing of space time could appear as expansion when looking through the lens of a 3 dimensional observer or am I misunderstanding the affects of gravity on space-time and its relationship to light?  
> **username_4**: *Things behind me would be accelerating slower towards the singularity things in front of us would be accelerating faster.* Which singularity are you talking about?  
> **username_5**: That won't fit in a perpendicular line of sight, at least in a flat space.  
> **username_6**: "How does GR affect redshift calculations"? Cosmological redshift *is* a GR effect. Its similarity to a Doppler shift caused by motion is only true for small redshifts.  
> **username_7**: I don't think this question should be closed as a "personal theory". The OP makes clear that probably he's not right, and just want to know where the flaw is".  
> **username_7**: But yeah, you might want to delete the sentence "_here is a theory_" in order not to upset people. You might even want to read up on the difference between theory, hypothesis, and ideas :)  
> **username_0**: Rob - you are saying that we know the GR redshift and it would not account for the quantity we observe in the visible universe?  
> **username_0**: Pela - Thanks for correcting my scientific grammar. so I have a hypothesis based on possibly misunderstood ideas.  

---

## 1 answers

### Answer by username_7 on 2019-03-20. Score: 2

If you work out the equations of motion for the gravitational free-fall collapse of a clouds of particles (or galaxies), you will find that, from the point of view of *any* of these particles, all other particles appear to be approaching. This is true in both Newtonian theory and general relativity.

The calculation is found in numerous text books and lecture notes, e.g. [Susanne Höfner's](http://www.astro.uu.se/~hoefner/astro/teach/apd_files/apd_collapse.pdf), but a qualitative argument goes like this:

From your point of view, sitting on one of the particles, a particle farther from the center of the cloud does "feel" a smaller gravitational pull from the central particles. This is, I think, the reason that you think it should accelerate more slowly. However, any particle feels the gravity from *all* particles that are closer to the center, so the farther you are from the center, the more particles will attract you. On the other hand, the gravity from all particles that are *farther* away from the center cancels out, so you don't feel those.

This is, in essence, [Newton's shell theorem](https://en.wikipedia.org/wiki/Shell_theorem), and it turns out to imply that *all particles reach the center at the same time*. The distance between each particle is getting smaller and smaller, until the cloud collapses into an point after a a time inversely proportional to the square root of the density.

This is exactly opposite to what is observed.


---

