Here's what I most don't get about the Big Bang...

[scubadude]

If there is a quantity of matter large enough, even light cannot escape it's grasp. It is then called a black hole.

Here's the question: If the Big Bang created all of the matter in the universe, including all of the dark matter we cant see and all of the matter inside black holes, why didn't it collapse into a giant black hole immediately? If the speed limit of the universe is lightspeed how could anything escape? The matter density of the entire universe concentrated into a point source.

Scuba

[Tikki]

1. The Schwarzschild limit does not apply to rapidly expanding matter.

Tikki

[qazplm]

2. space can expand faster than the speed of light

and inflation at the moment after the big bang was certainly faster than the speed of light.

Probably multiple reasons why it didnt all collapse back.

[MUAD_DIB]

3. One theoretical model of the BB is that this universe

actually collided/bumped with a universe full of matter.

The result was not a infinitesimally small area rapidly expanding, but a capture or introduction of matter from someplace else.

[scubadude]

4. I'm still not getting it folks.

The Swartchild radius is caused by highly compacted matter, and nothing can escape it beyond the small amount of matter that boils off as described by Hawking over billions of years.

Inflation may be a partial answer, but I saw no scientific argument answering my question before the inflationary model came into vogue so I don't think this covers it.

Perhaps in the early universe gravity didn't exist? I'm doing a bit of guessing here but I recall that some of the fundamental forces didn't freeze out until some small fraction of a second after the big bang. I'm still not getting it.

It still seems to me that very early on the universe should have collapsed in a black hole. I recall there being some theory that there are many tiny black holes zipping around in space since the Big Bang.

I wish I had more brains! Or more teaching. Or some physics PHD's for friends instead of Lawyers and such.

Scuba

[Orrex]

5. I'm weak on the physics, but your question suggests something about how you're thinking about this.

Your question about post-Bang expansion is framed as though you're thinking of the Big Bang expanding into pre-existing space and therefore constrained by the laws of that space.

The current thinking, as I understand it, is that space itself expanded as part of the Big Bang. And, as was mentioned up-thread, space can expand at faster than the speed of light.

That probably doesn't really settle it for you, but I think that the way you're asking the question is getting in the way of the right answer.



Of course, I may be way off about this, so take it with a grain of salt. Unless I'm right, in which case you should praise my genius.

[qazplm]

7. makes sense to me

then again Im weak in physics too, that's why Im a lawyer lol

But seems to me if space is expanding, and doing so faster than the speed of light, then very quickly even if the S-radius applied at moment or right after the Big Bang, by the time space expansion stops inflating and moving faster than the speed of light, most everything is already outside of the limit, i.e. density dissipates so rapidly that by the time inflation is over, there is no longer any region where gravity is strong enough to even form a black hole.

[Angleae]

6. The normal laws of physics didn't apply until after the big bang.

[Random_Australian]

8. Ok, take a look at the reasoning for how black holes are formed.

Situation A: Normal black hole

Step 1: The iron ash core of an old, large star is supported by electron degeneracy pressure, provided it is very small.

Step 2: Electron degeneracy pressure is overcome and all the matter converts to neutrons and is supported against further collapse by the Pauli exclusion principle/neutron degeneracy pressure.

This is the strongest substance known to be possible; its ability to support massive impacts and energies without much happening to it is what gives rises to supernovae (as the collapsing star bounces off the neutron core, high-Z nuclear burning and all)

Step 3: With enough mass, the gravitational pressure can overcome the neutron degeneracy pressure and since there is no known mechanism by which it could prevent collapse, we must surmise it does, and does so indefinately. At some point light itself will not be able to escape from a small radius around it.


Situation B: The Big, Big, Big Bang

Step 1: There is so much energy flying around in the quark-gluon plasma that there none of this "not enough energy to prevent collapse" stuff. So it doesn't immediately collapse, and expands into whatever space is given it. Give it a while, yes, and it will have to collapse back. But not just yet.

Step 2: Space is expanding faster than the speed of light, with the matter expanding into it. This promptly expands the matter past the critical density where it would all be black-holey. The mass still has enough energy (I say mass, but it is a while before we get anything other than matter-antimatter creation and annihilation) to keep flying out pretty fast, in fact.

[BadgerKid]

9. Here's my cycle idea.

The stepwise formation scenario is very interesting. Are you suggesting a cycle between black hole formation and big bang type expansions?

If so, black hole evaporation via matter-antimatter particle pairs could be the black hole's response to hugely increasing gravitation pressure since no (known) further particle degeneracy pressure is present.

[Random_Australian]

12. It was set out in steps to be easy to read - in reality, it's continuous.

And no, I'm not suggesting cyclical balck hole formation. I contrasted two different scenarios, one in which black holes form and one in which they don't need to.

Uh, and in the big bang, further particle degeneracy was present as it was dealing with bosons not fermions. :)

Also, I don't see what you're getting at in that last statement.

[scubadude]

10. I have been researching and have found that my question was answered in Sci Am

but of course to get to the answer you have to pay. That totally ticks me off because for over 20 years I subscribed. Now I have the internet....

I found another answer, which I believe was at least alluded to in part by someone in the thread:

Why did the universe not collapse and form a black hole at the beginning?

Sometimes people find it hard to understand why the big bang is not a black hole. After all, the density of matter in the first fraction of a second was much higher than that found in any star, and dense matter is supposed to curve space-time strongly. At sufficient density there must be matter contained within a region smaller than the Schwarzschild radius for its mass. Nevertheless, the big bang manages to avoid being trapped inside a black hole of its own making and paradoxically the space near the singularity is actually flat rather than curving tightly. How can this be?

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 while space-time is not. The curvature can come from the temporal parts of the space-time metric which measures the deceleration of the expansion of the universe. So the total curvature of space-time 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. The Schwarzschild solution of the gravitational equations is static and demonstrates the limits placed on a static spherical body before it must collapse to a black hole. The Schwarzschild limit does not apply to rapidly expanding matter.


What that boils down to in my mind is it took a long time for the expansion pressure was low enough to allow the formation of black holes. Once it was, the density of the expanding matter was too low too form them.

Am I on the right track here?

On edit I just realized this is basically a restatement of what you just said! Black-holey indeed Random_Australian!

Thank you all,

Scuba

[scubadude]

11. All very good answeres.

I guess I was stuck in the space is defined by matter vortex.

Perhaps expanding space caused the big bang.

Imagine a black hole, sitting there infinitely chomping down all matter it comes in contact with. Eventually the space which surrouds it is thinned out to a greater extent than the space within, as defined by the amount of matter within. Suddenly this "vacuum pressure" of space begins to escape somewhere, sucking out the black hole creating matter.

It's not done yet.

Scuba