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Angelo

If there was a big bang 14 or so billion years ago and all mass

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is and has been moving away from this point for 14 billion years wouldn't this indicate that there would be a 14 billion year wide void with the center of this being where the big bang happened and matter forming a sort of expanding shell moving ever outward?   In the absence of this how can the big bang theory survive?

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The BB wasn't an explosion from a single point. It was an expansion of all the hot, dense matter and its evolution into a cooler, less dense state.

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Posted (edited)
4 minutes ago, Phi for All said:

The BB wasn't an explosion from a single point. It was an expansion of all the hot, dense matter and its evolution into a cooler, less dense state.

So that theory says that all matter was widespread and hot just for some unknown reason all started moving and cooling at the same moment.  What connected all this matter to begin changing at the same instant  It's not like an event in the Milky Way can effect another galaxy on the edge of the universe simultaneously

Edited by Angelo

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3 minutes ago, Angelo said:

So that theory says that all matter was widespread and hot just for some unknown reason all started moving and cooling at the same moment.  What connected all this matter to begin changing at the same instant  It's not like an event in the Milky Way can effect another galaxy on the edge of the universe simultaneously

The expanding universe is why the whole universe is cooling.  That is why there is background microwave radiation.

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30 minutes ago, Angelo said:

is and has been moving away from this point for 14 billion years wouldn't this indicate that there would be a 14 billion year wide void with the center of this being where the big bang happened and matter forming a sort of expanding shell moving ever outward?   In the absence of this how can the big bang theory survive?

The universe has always been (roughly uniformly) full of matter/energy. This means that the early universe was very hot and dense. As the universe expanded it cooled and got less dense.

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14 minutes ago, Bufofrog said:

The expanding universe is why the whole universe is cooling.  That is why there is background microwave radiation.

But the last poster said that the universe was not expanding from a single point, which with the size of the universe considered why would all mass start expanding at the same time.  The questions must be answered as without a single starting point it needs to be explained as to why expansion happened form multiple points at the same time, if it did

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21 minutes ago, Angelo said:

So that theory says that all matter was widespread and hot just for some unknown reason all started moving and cooling at the same moment.  What connected all this matter to begin changing at the same instant  It's not like an event in the Milky Way can effect another galaxy on the edge of the universe simultaneously

This is actually one of the big unanswered questions. The current best hypothesis is that the universe achieved equilibrium when it was very small and then rapidly expanded (inflation).

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3 minutes ago, Strange said:

The universe has always been (roughly uniformly) full of matter/energy. This means that the early universe was very hot and dense. As the universe expanded it cooled and got less dense.

Again if it is expanding for 14 billion years this indicates a perfectly cool center void of mass as the expanding mass carried the heat away.  Without the void the big bang can not be scientifically verified

1 minute ago, Strange said:

This is actually one of the big unanswered questions. The current best hypothesis is that the universe achieved equilibrium when it was very small and then rapidly expanded (inflation).

This hypothesis could be at least partially verified by a void at the center of all expansion that should be traceable by reversing observed expansion directions

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2 minutes ago, Angelo said:

Again if it is expanding for 14 billion years this indicates a perfectly cool center void of mass as the expanding mass carried the heat away.  Without the void the big bang can not be scientifically verified

If you have a cloud of gas or dust and let it expand, it will spread uniformly (each atom or particle will move away from every other). This will lead to a larger, less dense cloud. But it won't have a void in the middle.

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Just now, Strange said:

If you have a cloud of gas or dust and let it expand, it will spread uniformly (each atom or particle will move away from every other). This will lead to a larger, less dense cloud. But it won't have a void in the middle.

What is the evidence that the universe began as a cloud?  Also since all galaxies are observed moving away from each other there needs to be a center.  Also if a cloud expanded it would become less dense than the cloud prohibiting solid mass from forming.

See the more questions one ask the more a computer program becomes viable or we must accept that all ideas that fail are flawed.   So what if background radiation is observed, there are as many reasons for this as there are things in the universe that remain unknown it does not need to be a big bang which has now become a bunch of little bangs that all happened together

 

Sure

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3 minutes ago, Angelo said:

Without the void the big bang can not be scientifically verified

I think the big bang theory does not require, or even allow, a center and a void to be observed. If such a void could be observed I think it could be the basis for some new theory replacing big bang model (not very likely as far as I know). Since the big bang has no center point every observer everywhere will see them self more or less in the center of an expanding observable universe. We on earth see similar background microwave radiation coming from each direction. And the model describes that the same holds for other (hypothetical) observers in other locations in the observable universe. The model may or may not be correct for what is beyond the observable universe.

A common analogy is an expanding balloon. Short version with an animation: http://www.astro.ucla.edu/~wright/balloon0.html

 

 

 

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14 minutes ago, Angelo said:

What is the evidence that the universe began as a cloud? 

The fact that we have a model based on that assumption, and the model has been shown to be consistent with observation.

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Also since all galaxies are observed moving away from each other there needs to be a center. 

The is no center in cosmology. This is either because the universe is infinite or because it is "finite but unbounded" (a 2D analogy is the surface of a sphere; that has a finite area but no edge).

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Also if a cloud expanded it would become less dense than the cloud prohibiting solid mass from forming.

The average density decreases but expansion is sufficiently slow that there is time for gravity to cause collapse to happen in small areas so that stars, galaxies and planets can form.

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So what if background radiation is observed, there are as many reasons for this as there are things in the universe that remain unknown 

There are other possible explanations for the CMB (but not many). But none that are consistent with all the evidence.

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Our 'observable' or 'causal' universe began almost 14 billion years ago as in a hot dense state, and extremely small size.
At various times in its early life it consisted of differing states, and evolved, as it cooled, from energetic fields, through radiation and matter as we know it.
As it cooled, it 'expanded', meaning the separation between objects, on a scale that isn't overridden by gravity, increased inversely proportional to its temperature drop. When atoms first formed from the earlier plasma, 300,000 years after the BB event, the universe was approx. 1040 times hotter than its current ( CMB ) temperature of 2.7 deg K, so it has expanded, since then, 1040 fold ( simple gas laws ).

The universe did not expand into anything, at least not anything that could affect us, as there is no causal connection with anything outside our causal or observable universe ( although during certain eras, the causal universe was different in size, and is getting smaller all the time ).
For all intents and purposes, we can consider the observable universe ALL that there is, as anything 'outside' cannot affect us.

Ask questions, regarding anything that confuses you.
That is the way we all learn.

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Posted (edited)
3 hours ago, Angelo said:

But the last poster said that the universe was not expanding from a single point, which with the size of the universe considered why would all mass start expanding at the same time.

We are trying to tell you that the universe started off from an unimaginably small, hot and dense point.  There was not an explosion, but an expansion of that point.  Every part of the universe was expanding.  Mass was not expanding, the universe was expanding.  There was no mass in the early universe, atoms formed around 370,000 years after the big bang.

 

3 hours ago, Angelo said:

The questions must be answered as without a single starting point it needs to be explained as to why expansion happened form multiple points at the same time, if it did

The universe is still expanding.  All the non-gravitationally bound galaxies are move away from each other.  The are all moving away from each other because the universe is expanding.  The galaxies are not moving away from some point in space.

3 hours ago, Angelo said:

Again if it is expanding for 14 billion years this indicates a perfectly cool center void of mass as the expanding mass carried the heat away.  Without the void the big bang can not be scientifically verified

Again the universe is not expanding away from a point in space.  That would be easy to determine from the velocity of the galaxies.  The galaxies are all moving away from each other.  It is like, not exactly, but like a raisin bread loaf rising as it is cooked, all of the rasins move away from each other and there is no void in the middle of the loaf.

As the universe expands it cools.  Since every point in the universe is expanding the entire universe is cooling not just the nonexistent center.

 

3 hours ago, Angelo said:

This hypothesis could be at least partially verified by a void at the center of all expansion

If there were this void that you propose, that would not support the big bang theory that would disprove it!

 

3 hours ago, Angelo said:

What is the evidence that the universe began as a cloud?  Also since all galaxies are observed moving away from each other there needs to be a center.  Also if a cloud expanded it would become less dense than the cloud prohibiting solid mass from forming.

The poster brought up a cloud as an analogy.  The universe is not a cloud and it is not a raisin loaf.

 

Edited by Bufofrog

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One important point when we state the universe expanded from a miniscule finite point we are referring to our Observable portion of the universe. The remainder of the universe could be infinite or finite. We simply do not know.

 Think of our observable portion as the region of shared causality with regards to the BB. It is as mentioned expansion from a hot dense state with which our entire observable portion resides within that portion. You cannot look at any direction and state the BB exists that away.

It is all around us and completely surrounds us.

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