Is The Big Bang still a Black Hole.

[Baluncore]

Following a Big Bang, if the Universe expanded at the speed of light, then the Laws of Physics would have come into play long before the radius of the Universe passed it's own Schwarzschild radius.

Does that mean the Universe cannot keep expanding forever ?
or maybe that we exist inside a Black Hole ?

Descriptions of Black Holes always take a fearful view from outside. But what if we were inside, what would the event horizon look like ?
Would light attempting to leave our Black Hole of a Universe appear to be red shifted ?

 

[DiracPool]

or maybe that we exist inside a Black Hole ?

I was out mowing my lawn the other day. I don't think you can mow your lawn inside a black hole, matter is scrunched up too tight for the lawnmower blades to work effectively. So I'd say no, we don't exist inside a black hole.

Would light attempting to leave our Black Hole of a Universe appear to be red shifted?

Light attempting to leave a black hole will fail in that attempt. That's kind of the definition of a black hole, light cannot escape from it.

Although... Lee Smolin thinks that our universe may be the "backwash" of the formation of a black hole in an alternate universe. I call this the "law of the minimization of mystery." Black holes are mysterious, the big bang is mysterious. Maybe there's some connection? Yes, the singularity. However, even if Smolin's musings are correct, that doesn't mean our universe is a black hole, per se. It just means that our big bang was an extended conduit of the formation of a black hole in another universe, at least according to Smolin.

 

[Baluncore]

None of that explains how the Universe passed the point at which our BB Universe escaped from it's own Black Hole.
Either the Big Bang is mythical or the physics of Black Holes is wrong. The concepts appear to be mutually incompatible.

 

[jtbell]

Look down at the bottom of this page and you'll see links to some of the many previous discussions here on whether the Big Bang was a black hole. Also see Is the big bang a black hole? from the sci.physics FAQ.

 

[bapowell]

Either the Big Bang is mythical or the physics of Black Holes is wrong. The concepts appear to be mutually incompatible.

Or your understanding of each is lacking.

 

[phinds]

None of that explains how the Universe passed the point at which our BB Universe escaped from it's own Black Hole.
Either the Big Bang is mythical or the physics of Black Holes is wrong. The concepts appear to be mutually incompatible.

You would do well to read up a bit on just what the big bang IS (and isn't). As bapowell suggests, you clearly haven't got it yet.

 

[Drakkith]

I believe the key thing from Jtbell's link is the following snippet:

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.

 

[Baluncore]

I agree I have not got it.
If I did I would not have asked the question.
As it turns out, I'm not the first to ask that question, so at least I am thinking.

Funny how a quick search of the forums does not throw up useful links, so I post and then at the bottom of the page appears all the useful links I was searching for. It must be magic.

So where is there a help page for the advanced search, keyword or phrase entry.

 

[Drakkith]

Click Search at the top of the page, then on the dropdown menu, click Advanced Search.

 

[marcus]

I agree I have not got it.
If I did I would not have asked the question.
As it turns out, I'm not the first to ask that question, so at least I am thinking.
...

At least by my standards you are thinking well and are obviously motivated to learn/understand so everything here is right and normal IMHO, but I'm no judge. People differ as to how they see this kind of question, and the spirit in which they ask it.
FWIW I'll give you my take.
GR is an equation dating back to 1915 before quantum mechanic. GR solutions can have failure points where they blow up and fail to give meaningful numbers.

A solution to the GR equation is a space-time geometry. BH and BB are two different solutions actually CLASSES of solutions, there are various BH solutions depending on whether or not it's rotating and electrically charged etc etc.

In the BB solution the geometry has somehow gotten started expanding. Distances are increasing typically at superluminal rates. I can't picture a classical large-scale BH collapse occurring in that context.
The usual BH solution, called Schwarzschild BH, has a surrounding geometry which is NON-EXPANDING. Oooops just got a phone call, have to go

 

[marcus]

Baluncore, I just got back. You know the condition of criticality for the Schw. BH. If you get a certain concentration of mass within a certain radius in a non-expanding space then it will form a BH. Or if the rate of expansion is so slow it can be neglected.
But that does not mean that the same concentration of mass would always form a BH in a different context---these are two different solutions of the GR equation, the math would not necessarily work.
An extremely rapidly expanding space (high Hubble rate H) can TAKE a lot higher density of mass without collapsing.

I don't want to go into anything technical just give an intuitive assurance that it is OK. The very early high density rapid expansion phase does not actually spell BH. Other people, if you ask further, can give details. Or if it turns out to be easy to understand from what you find by doing a search, so much the better.

Oh, both the BB and the BH solutions have SINGULARITIES which are failure points where the classic 1915 GR blows up and stops being reliable. So that is just a symptom that the man-made theory is incomplete and fails at very high density, so the theory needs improvement. People are working on improved (possibly quantum) versions of GR that do NOT have singularities ether at start of BB expansion or at the center of the BH. In some of these proposed improved "non-singular" versions there are quantum effects appearing at extreme density that make gravity momentarily repellent and cause the collapse to rebound, triggering rapid expansion "out the back door" causing a new region of spacetime to occur, not intersecting with ours. So there actually (according to some quantum variants of GR) could be a bounce in the pit of a BH, spreading out into a "somewhere else" non-intersecting region of spacetime.

In fact, Jorge Pullin is giving a talk about that this week at the big GR20 conference

 

[jtbell]

Funny how a quick search of the forums does not throw up useful links, so I post and then at the bottom of the page appears all the useful links I was searching for. It must be magic.

So where is there a help page for the advanced search, keyword or phrase entry.

The forum search is pretty primitive. Try using Google instead. For some reason the "Search PF via Google" option doesn't work for me right now; it hangs at "Loading...". Instead you can restrict a general Google search (from Google's home page) to search only Physics forums:

black hole big bang site:physicsforums.com