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Big bang versus black hole

by Naty1
Tags: bang, black, hole, versus
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Feb8-13, 06:33 PM
P: 5,632
In this FAQ at the Baez website, the big bang singularity is contrasted with a black and white hole as a possible beginning of our universe.

Is the Big Bang a black hole?

[I'm not interested in answering the title question,which is NO, but rather exploring the differences.]

A few major differences are outlined:

The black hole singularity always lies on the future light cone, whereas astronomical observations clearly indicate a hot Big Bang in the past.....

The short answer is that the Big Bang gets away with it because it is expanding rapidly near the beginning and the rate of expansion is slowing down. Space can be flat even when spacetime is not. Spacetime's curvature can come from the temporal parts of the spacetime metric which measures the deceleration of the expansion of the universe. So the total curvature of spacetime is related to the density of matter, but there is a contribution to curvature from the expansion as well as from any curvature of space.....
So, the first sentence appears to be a major distinction between a BB and a BH. ok.

Three questions:

what about the temperature difference between the two....less than 3 degrees K for many black holes and 1028 degrees K for the big bang....Does this manifest in the differences or is temperature relatively unimportant?

Also, Is SPACE hardly curved at the big bang, just time, while for a black hole both space and time are severely curved?? If so, does the extreme curvature of time relate to the temperature difference? to the initial expansion/repulsion?

Do we have any quantum insights yet that support, contradict or offer other insights?

edit: from another thread, I saved this partial insight:

Pervect: "Because the stress-energy tensor for expanding matter is different from the stress-energy tensor of non-expanding matter, you can have compact, dense, expanding objects that are not black holes." ok.
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Feb8-13, 06:49 PM
P: 5,632
I posted this elsewhere:
Is Spacetime Quantized? Loop quantum gravity even makes precise predictions about the geometry of spacetime at the Planck scale.
Sounds interesting, but I do not have any of those predictions.

I checked Lee Smolin's THREE ROADS TO QUANTUM GRAVITY [year 2000] and he discusses LQG
in terms of evolving [Penrose] spin networks in some detail, and has done research himself, but says nothing about the geometry relative to BH and BB...

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