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Did the Big Bang happen at a point?How is it possible for astronomers to see something 13B light years away?How to test whether galaxies are moving away from each other in a static background or whether space is being created beween them?Is it possible that universe might not be speeding up expansion?Evidence for expansion of spaceWhy do galaxies “disappear?”Expanding universe and speed of lightCan redshift occur from relative velocity or just from expanding spaceThe speed of the outer stars of galaxiesGalaxies moving in fixed background or fixed in expanding backgroundWhat does general relativity say about the relative velocities of objects that are far away from one another?

5

$begingroup$

So, we observe that galaxies are moving apart (on average) and the further away from us they are the faster they are moving away from us. If space was expanding that would explain this.

However, I imagine that if a primordial explosion happened then at some point close to where the explosion happened things would not move much, and they would be moving faster the further away you were from "ground zero".

But if we were not near ground zero there should be some anisotropy in the speeds we observe, is that correct? There should be a "ground zero" in the "explosion model", right??

However, regardless of the "ground zero" issue, do we (or could we) distinguish between a uniform "explosion" model and the idea that space is expanding?

general-relativity astronomy

share|cite|improve this question

edited 3 hours ago

Paul Young

asked 5 hours ago

Paul YoungPaul Young

1,628319

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Possible duplicate of Did the Big Bang happen at a point?
  $endgroup$
  – pela
  4 hours ago
  

  
  
  
  

add a comment | 

5

$begingroup$

So, we observe that galaxies are moving apart (on average) and the further away from us they are the faster they are moving away from us. If space was expanding that would explain this.

However, I imagine that if a primordial explosion happened then at some point close to where the explosion happened things would not move much, and they would be moving faster the further away you were from "ground zero".

But if we were not near ground zero there should be some anisotropy in the speeds we observe, is that correct? There should be a "ground zero" in the "explosion model", right??

However, regardless of the "ground zero" issue, do we (or could we) distinguish between a uniform "explosion" model and the idea that space is expanding?

general-relativity astronomy

share|cite|improve this question

edited 3 hours ago

Paul Young

asked 5 hours ago

Paul YoungPaul Young

1,628319

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Possible duplicate of Did the Big Bang happen at a point?
  $endgroup$
  – pela
  4 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

So, we observe that galaxies are moving apart (on average) and the further away from us they are the faster they are moving away from us. If space was expanding that would explain this.

However, I imagine that if a primordial explosion happened then at some point close to where the explosion happened things would not move much, and they would be moving faster the further away you were from "ground zero".

But if we were not near ground zero there should be some anisotropy in the speeds we observe, is that correct? There should be a "ground zero" in the "explosion model", right??

However, regardless of the "ground zero" issue, do we (or could we) distinguish between a uniform "explosion" model and the idea that space is expanding?

general-relativity astronomy

share|cite|improve this question

edited 3 hours ago

Paul Young

asked 5 hours ago

Paul YoungPaul Young

1,628319

$endgroup$

share|cite|improve this question

edited 3 hours ago

Paul Young

asked 5 hours ago

Paul YoungPaul Young

1,628319

share|cite|improve this question

edited 3 hours ago

Paul Young

asked 5 hours ago

Paul YoungPaul Young

1,628319

asked 5 hours ago

Paul YoungPaul Young

1,628319

asked 5 hours ago

Paul YoungPaul Young

1,628319

1 Answer
1

active

oldest

votes

4

$begingroup$

It is a misconception that the big bang happened at a point. It did not. There is no ground zero point (in space) where you could point and say, this is where the explosion happened. Space is expanding everywhere at the same rate, and everything is getting farther away from everything.

Now this is not completely true, because galaxies are getting usually farther away from each other, because in the intergalactic space, expansion is dominant.

But inside galaxies, gravity dominates, so space does not expand inside galaxies.

So on the bigger scale, between the intergalactic voids of space, where expansion dominates space itself is expanding, and this expansion seems to be accelerating. Now an explosion as you say could not do this, because to have an ever accelerating expansion you need more and more energy (whatever is causing expansion, like dark energy or negative density). An explosion cannot do that.

So the big bang did not happen at a point in space, but it happened everywhere at the same time.

There is no center of the universe or as you say a ground zero point.

The universe is not like a ball expanding, there is nothing outside the universe that it is expanding into.

Please see here:

Did the Big Bang happen at a point?

share|cite|improve this answer

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Got it - that the expansion seems to be accelerating seems very key to me
  $endgroup$
  – Paul Young
  4 hours ago
  

  
  
  
  

add a comment | 

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4

$begingroup$

It is a misconception that the big bang happened at a point. It did not. There is no ground zero point (in space) where you could point and say, this is where the explosion happened. Space is expanding everywhere at the same rate, and everything is getting farther away from everything.

Now this is not completely true, because galaxies are getting usually farther away from each other, because in the intergalactic space, expansion is dominant.

But inside galaxies, gravity dominates, so space does not expand inside galaxies.

So on the bigger scale, between the intergalactic voids of space, where expansion dominates space itself is expanding, and this expansion seems to be accelerating. Now an explosion as you say could not do this, because to have an ever accelerating expansion you need more and more energy (whatever is causing expansion, like dark energy or negative density). An explosion cannot do that.

So the big bang did not happen at a point in space, but it happened everywhere at the same time.

There is no center of the universe or as you say a ground zero point.

The universe is not like a ball expanding, there is nothing outside the universe that it is expanding into.

Please see here:

Did the Big Bang happen at a point?

share|cite|improve this answer

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Got it - that the expansion seems to be accelerating seems very key to me
  $endgroup$
  – Paul Young
  4 hours ago
  

  
  
  
  

add a comment | 

4

$begingroup$

It is a misconception that the big bang happened at a point. It did not. There is no ground zero point (in space) where you could point and say, this is where the explosion happened. Space is expanding everywhere at the same rate, and everything is getting farther away from everything.

Now this is not completely true, because galaxies are getting usually farther away from each other, because in the intergalactic space, expansion is dominant.

But inside galaxies, gravity dominates, so space does not expand inside galaxies.

So on the bigger scale, between the intergalactic voids of space, where expansion dominates space itself is expanding, and this expansion seems to be accelerating. Now an explosion as you say could not do this, because to have an ever accelerating expansion you need more and more energy (whatever is causing expansion, like dark energy or negative density). An explosion cannot do that.

So the big bang did not happen at a point in space, but it happened everywhere at the same time.

There is no center of the universe or as you say a ground zero point.

The universe is not like a ball expanding, there is nothing outside the universe that it is expanding into.

Please see here:

Did the Big Bang happen at a point?

share|cite|improve this answer

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Got it - that the expansion seems to be accelerating seems very key to me
  $endgroup$
  – Paul Young
  4 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

It is a misconception that the big bang happened at a point. It did not. There is no ground zero point (in space) where you could point and say, this is where the explosion happened. Space is expanding everywhere at the same rate, and everything is getting farther away from everything.

Now this is not completely true, because galaxies are getting usually farther away from each other, because in the intergalactic space, expansion is dominant.

But inside galaxies, gravity dominates, so space does not expand inside galaxies.

So on the bigger scale, between the intergalactic voids of space, where expansion dominates space itself is expanding, and this expansion seems to be accelerating. Now an explosion as you say could not do this, because to have an ever accelerating expansion you need more and more energy (whatever is causing expansion, like dark energy or negative density). An explosion cannot do that.

So the big bang did not happen at a point in space, but it happened everywhere at the same time.

There is no center of the universe or as you say a ground zero point.

The universe is not like a ball expanding, there is nothing outside the universe that it is expanding into.

Please see here:

Did the Big Bang happen at a point?

share|cite|improve this answer

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

$endgroup$

share|cite|improve this answer

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625

answered 4 hours ago

Árpád SzendreiÁrpád Szendrei

4,5571625