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Author Topic: How has the Universe been cooling since the big bang?  (Read 19254 times)

Offline LeeE

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How has the Universe been cooling since the big bang?
« Reply #25 on: 28/12/2008 22:06:01 »
Yup - same quantity of energy, just spread thinner.

Mmm... there's a thought;  Is entropy chasing the expansion of the universe?  If the universe wasn't expanding, the energy within it would would nearly completely equalise relatively quickly, leaving no, or extremely low, energy gradients where work could be done.  From an anthropic point of view, expansion would then seem to be necessary for a universe where work can be done on a long-term basis, as it results in an energy gradient for as long as the expansion continues.
 

Offline Bikerman

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How has the Universe been cooling since the big bang?
« Reply #26 on: 28/12/2008 22:35:14 »
Well, yes I suppose so. It depends when you want to 'stop' the universe. Obviously if you stop it at the singularity then minimum entropy reigns and nothing happens.
 

Offline Mr. Scientist

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How has the Universe been cooling since the big bang?
« Reply #27 on: 29/12/2008 00:48:45 »
I understand that there has been electromagnetic Radiation that has been covering all matter sense the big bang.... How does this in effect create the cooling of the universe?

Because, as you might imagine, the continuous expansion of spacetime means that the real matter and energy contained within it is being diluted more and more; this added area, an infinite amount of expansion, is cooling the universe down.

If you traced the evolution back to some point, only a few chronons after big bang, we find the energy all stacked up very close proximity to each other, in a very hot gas of particles.
 

Offline LeeE

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How has the Universe been cooling since the big bang?
« Reply #28 on: 30/12/2008 20:05:40 »
Well, yes I suppose so. It depends when you want to 'stop' the universe. Obviously if you stop it at the singularity then minimum entropy reigns and nothing happens.


Yup, what I was thinking.  It would have consequences for an expanding universe where the rate of expansion was decreasing, or where expansion ceased and it started to contract.  In the first case, of decreasing expansion, entropy could overtake the rate of expansion, and in the second case, where a universe had reached the limit of expansion and started to contract, entropy would bring about the end of everything well before the big crunch.

A universe that increases it's rate of expansion seems to be the only really long-term solution.
 

Offline yor_on

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How has the Universe been cooling since the big bang?
« Reply #29 on: 01/01/2009 12:56:31 »
You also have the proposal where all types of energy and 'anti energy' in our universe together would become zero and null.
If that would be true expansion won't mean a thing, as well as spontaneous matter creations and virtual particles.

Seen that way our universe as easily could be just one like those...
Virtual particles, 'popping up' and then disappearing.
And the 'time' we have for defining our direction in spacetime.
Would then be much the same as for defined inside a VMO.
As all energy becomes null.
 

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How has the Universe been cooling since the big bang?
« Reply #29 on: 01/01/2009 12:56:31 »

 

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