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tommac
2009-May-05, 08:30 PM
If the entire universe was the size of a golf ball or smaller then wouldnt it of been a black hole? How could anythign escape it?

grant hutchison
2009-May-05, 09:28 PM
Different spacetime geometries. The Schwarzschild metric is a static solution, which doesn't apply to expanding space.
More here (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/universe.html).

Grant Hutchison

01101001
2009-May-05, 09:38 PM
If the entire universe was the size of a golf ball or smaller then wouldnt it of been a black hole?

Ned Wright Cosmology FAQ: Is the Big Bang a Black Hole? (http://www.astro.ucla.edu/~wright/cosmology_faq.html#HOLE)


The Big Bang is really nothing like a black hole. The Big Bang is a singularity extending through all space at a single instant, while a black hole is a singularity extending through all time at a single point. For more, see the sci.physics FAQ (http://www.weburbia.com/physics/universe.html).

Sci.physics Relativity FAQ: Is the big bang a black hole? (http://www.weburbia.com/physics/universe.html)


This question can be made into several more specific questions with different answers.

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.

Et cetera, et cetera, et cetera.

Gandalf223
2009-May-06, 12:53 AM
If the entire universe was the size of a golf ball or smaller then wouldnt it of been a black hole? How could anythign escape it?

Before the BB, there wasn't a universe, and nobody can rationally assume that the physics of the universe as we know it, even existed or would have applied. Put another way, there was no such thing as a black hole prior to the big bang, because the physical laws that define a black hole had not yet come into existence.

BTW, before the BB, the universe wasn't the size of anything. There was no space, therefore there was no system of X,Y,Z coordinates to measure by. Everything we know, or think we know, about the universe around us, cannot be extrapolated to the pre-BB whatever-it-was.

Your question is not answerable, because nobody can make any reasonable statements about conditions prior to the big bang.

WayneFrancis
2009-May-06, 02:49 AM
Before the BB, there wasn't a universe, and nobody can rationally assume that the physics of the universe as we know it, even existed or would have applied. Put another way, there was no such thing as a black hole prior to the big bang, because the physical laws that define a black hole had not yet come into existence.

BTW, before the BB, the universe wasn't the size of anything. There was no space, therefore there was no system of X,Y,Z coordinates to measure by. Everything we know, or think we know, about the universe around us, cannot be extrapolated to the pre-BB whatever-it-was.

Your question is not answerable, because nobody can make any reasonable statements about conditions prior to the big bang.

Well put. The way I think of it is while the energy density was really high at the beginning the laws that dictate our current physics where not in play yet. With the rapid initial inflation that symmetry was broken but by then the expansion was fast enough that gravity couldn't pull the matter back in.

AndrewJ
2009-May-06, 03:38 AM
The structures of mature stars balance internal pressure with gravity. Perhaps there was an equivalent conflict in the hot, dense universe at BB. Am just speculating.

tommac
2009-May-06, 03:45 AM
Before the BB, there wasn't a universe, and nobody can rationally assume that the physics of the universe as we know it, even existed or would have applied. Put another way, there was no such thing as a black hole prior to the big bang, because the physical laws that define a black hole had not yet come into existence.

BTW, before the BB, the universe wasn't the size of anything. There was no space, therefore there was no system of X,Y,Z coordinates to measure by. Everything we know, or think we know, about the universe around us, cannot be extrapolated to the pre-BB whatever-it-was.

Your question is not answerable, because nobody can make any reasonable statements about conditions prior to the big bang.


I dont think I mentioned "before the BB"

tommac
2009-May-06, 03:47 AM
Different spacetime geometries. The Schwarzschild metric is a static solution, which doesn't apply to expanding space.
More here (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/universe.html).

Grant Hutchison

So what would happen during a big rip when it came across a black hole?

it would rip our solar system apart ... then rip our atoms apart ... would the big rip be able to rip a black hole?

Gandalf223
2009-May-06, 05:35 AM
I dont think I mentioned "before the BB"

Perhaps you didn't mean to, but close enough; you're certainly sending us back to the early stages of the BB. During the inflationary period (part of the Big Bang theory that is currently accepted by most of us) the proto-universe expanded immensely, to perhaps a large fraction of its current size. This expansion occurred after gravity and the strong nuclear force had split from the unified force, at about 10^-36 to 10^-32 second, but before the weak nuclear force and electromagnetism had split, which didn't occur until 10^-12 second into the life of the universe.

So a golf ball sized phase of the universe (assuming there were a scale to measure it, which there still wasn't) would have been somewhere around the time the strong nuclear force separated itself, and certainly long before there was any matter to form a black hole.

astromark
2009-May-06, 10:03 AM
At the moment this universe was the size of a golf ball it had such a expansion rate as to nullify any gravity force. We do not know what was the reason of such massive expansion then or now. Much has been written of this subject but, The actual answer is not forth coming... ' Was the BB a black hole' No. It was and still is the whole universe.
If we were to find evedance of galactic collapse, or areas of the universe not expanding, but actual shrinkage. The yes ... but NO. that is not so.

grant hutchison
2009-May-06, 12:29 PM
So a golf ball sized phase of the universe (assuming there were a scale to measure it, which there still wasn't) would have been somewhere around the time the strong nuclear force separated itself, and certainly long before there was any matter to form a black hole.All the mass-energy of the Universe was nevertheless present. The form it took isn't relevant: there's no "matter", in any conventional sense, inside a black hole, either.

Grant Hutchison

rommel543
2009-May-06, 03:55 PM
I've heard the term 'white hole' in the terms of the Big Bang. Instead of a matter crushing down to a singularity we had a singularity expanding into matter. Kind of like the tap and the drain. Matter came out of the white hole tap and down the black hole drain.

tommac
2009-May-06, 06:06 PM
So are you saying that at t0 ( the beginning of time ) the universe was "perhaps a large fraction of its current size"?



Perhaps you didn't mean to, but close enough; you're certainly sending us back to the early stages of the BB. During the inflationary period (part of the Big Bang theory that is currently accepted by most of us) the proto-universe expanded immensely, to perhaps a large fraction of its current size. This expansion occurred after gravity and the strong nuclear force had split from the unified force, at about 10^-36 to 10^-32 second, but before the weak nuclear force and electromagnetism had split, which didn't occur until 10^-12 second into the life of the universe.

So a golf ball sized phase of the universe (assuming there were a scale to measure it, which there still wasn't) would have been somewhere around the time the strong nuclear force separated itself, and certainly long before there was any matter to form a black hole.

tommac
2009-May-06, 06:07 PM
I've heard the term 'white hole' in the terms of the Big Bang. Instead of a matter crushing down to a singularity we had a singularity expanding into matter. Kind of like the tap and the drain. Matter came out of the white hole tap and down the black hole drain.

A white hole is also a black hole or at least still has all of the black hole capabilities.

rommel543
2009-May-06, 06:46 PM
A white hole is also a black hole or at least still has all of the black hole capabilities.

Yes and no, a white hole is a time reversal of a black hole. So yes it has all the attributes, but in reverse.

The schwarzschild wormhole model has a black hole on the entry point, suck matter into the wormhole, and a white hold on the exit point emitting the matter back out into space. Of course schwarzschild wormholes are unstable, collapsing as soon as they are created.

The fecund universes theory states that when a massive star collapses into a black hole it opens a 'doorway' creating a new universe in a different dimension. This doorway would present itself as a white hole in the other universe infinitely expanding, frozen in time in our universe as the black hole. Therefor we would be inside of a white hole at this moment, a child of a different Universe and dimension.

01101001
2009-May-06, 06:55 PM
So are you saying that at t0 ( the beginning of time ) the universe was "perhaps a large fraction of its current size"?

Have you defined what you mean by the "size of the universe"? Are you speaking of an observable universe, as others usually discuss when they mention the size?

The way you are using it seems to be about the entire universe, not just some observable part. Is that so? If so, how do you define "size" here?

tommac
2009-May-06, 10:26 PM
Yes and no, a white hole is a time reversal of a black hole. So yes it has all the attributes, but in reverse.

The schwarzschild wormhole model has a black hole on the entry point, suck matter into the wormhole, and a white hold on the exit point emitting the matter back out into space. Of course schwarzschild wormholes are unstable, collapsing as soon as they are created.

The fecund universes theory states that when a massive star collapses into a black hole it opens a 'doorway' creating a new universe in a different dimension. This doorway would present itself as a white hole in the other universe infinitely expanding, frozen in time in our universe as the black hole. Therefor we would be inside of a white hole at this moment, a child of a different Universe and dimension.

But a white hole is still a deep gravitational well with an EH that will suck in anything around it.

tommac
2009-May-06, 10:28 PM
Have you defined what you mean by the "size of the universe"? Are you speaking of an observable universe, as others usually discuss when they mention the size?

The way you are using it seems to be about the entire universe, not just some observable part. Is that so? If so, how do you define "size" here?


I was just quoting:
http://www.bautforum.com/space-astronomy-questions-answers/87942-universe-bh-moment-bb.html#post1483407

but really what I was saying is that if time and space only started after inflation which was being hinted at in that thread then there could be no "before" at t=0 the universe would have had a significant volume to it.

slang
2009-May-06, 10:48 PM
I was just quoting:
http://www.bautforum.com/space-astronomy-questions-answers/87942-universe-bh-moment-bb.html#post1483407

but really what I was saying is that if time and space only started after inflation which was being hinted at in that thread [...]

([bold mine] "that thread" is the CURRENT thread. Please be accurate in your descriptions, the discussion is already confusing enough as it is without links to other threads.)

How do you get the impression that that post "hints" that time and space only started after inflation? You so often seem to draw completely different conclusions from posts than I do, that I really want to know where that impression comes from..

ETA: the misunderstanding might well be on my side, I don't know.. that's why I'm asking :)

01101001
2009-May-06, 10:54 PM
I was just quoting:
http://www.bautforum.com/space-astronomy-questions-answers/87942-universe-bh-moment-bb.html#post1483407

Your own opening question mentioned:


If the entire universe was the size of a golf ball [...]

What did you mean by that? Observable universe or entire whole universe? If entire, like you said, what is your definition of "size"?

WayneFrancis
2009-May-07, 12:58 AM
So are you saying that at t0 ( the beginning of time ) the universe was "perhaps a large fraction of its current size"?

If the universe is not finite then it is infinite correct?
Well if I take something infinitely is size and squish it down by a factor of a billion how big is it?

It is still infinite!

I hate the analogy of the universe being this "small" object. All we know is that it was a "dense" object and because of inflation it became "less dense"

My understanding is that while they are trying to see if the universe is finite there is no evidence that it actually is.

Now if the universe is finite what does this mean?
Well again I would say that for the early universe it had little meaning because we had no real measuring stick to use to measure it. Now we do. We can use "c" as our measuring stick and can see that space is indeed expanding so in that way you can say that the universe is getting bigger.

I still like to think of it more like the universe is getting less dense while retaining the same mass because it more accurately describes what is actually happening.

WayneFrancis
2009-May-07, 01:03 AM
But a white hole is still a deep gravitational well with an EH that will suck in anything around it.

Wouldn't a white hole be repulsive? I.E. the closer you get to it the more energy you would have to use to reach it. In the end you would never get to it?

Actually never mind. A white hole would be a complete absence of matter and energy. By that and our understanding of gravity it would not have a repulsive effect as the absence of matter != anti gravity.

So I'm still confused why you would think a white hole would have a gravitational well at all.

WayneFrancis
2009-May-07, 01:07 AM
I was just quoting:
http://www.bautforum.com/space-astronomy-questions-answers/87942-universe-bh-moment-bb.html#post1483407

but really what I was saying is that if time and space only started after inflation which was being hinted at in that thread then there could be no "before" at t=0 the universe would have had a significant volume to it.

If you are trying to say that our laws of time and space break down at T0 then I don't think you'll find anyone disagreeing with you here.

tommac
2009-May-07, 02:02 AM
Do you need matter to form a black hole? Or could pure energy form one? For example you could create a black hole from a strong enough laser right?

tommac
2009-May-07, 02:06 AM
Wouldn't a white hole be repulsive? I.E. the closer you get to it the more energy you would have to use to reach it. In the end you would never get to it?. No ... in fact a white hole by definition is a time reversal of a black hole.

If you time reverse a black hole you will still see that there is a pull/deceleration. Acceleration is not reversible. So a white hole is as attractive as a black hole. A white hole is also a black hole.

tommac
2009-May-07, 02:09 AM
sorry re-read, my bad ... for some reason I thought that someone mentioned that time started after inflation ... after rereading I realize that nobody said that.


([bold mine] "that thread" is the CURRENT thread. Please be accurate in your descriptions, the discussion is already confusing enough as it is without links to other threads.)

How do you get the impression that that post "hints" that time and space only started after inflation? You so often seem to draw completely different conclusions from posts than I do, that I really want to know where that impression comes from..

ETA: the misunderstanding might well be on my side, I don't know.. that's why I'm asking :)

tommac
2009-May-07, 02:13 AM
Your own opening question mentioned:



What did you mean by that? Observable universe or entire whole universe? If entire, like you said, what is your definition of "size"?

I meant entire universe not just the visible part

tommac
2009-May-07, 02:14 AM
how close together would all of the mass in the universe need to be, to be a black hole.

tommac
2009-May-07, 02:16 AM
If the universe was infinite wouldnt we all be torn apart by ( an infinite amount of ) gravity?


If the universe is not finite then it is infinite correct?
Well if I take something infinitely is size and squish it down by a factor of a billion how big is it?

It is still infinite!

I hate the analogy of the universe being this "small" object. All we know is that it was a "dense" object and because of inflation it became "less dense"

My understanding is that while they are trying to see if the universe is finite there is no evidence that it actually is.

Now if the universe is finite what does this mean?
Well again I would say that for the early universe it had little meaning because we had no real measuring stick to use to measure it. Now we do. We can use "c" as our measuring stick and can see that space is indeed expanding so in that way you can say that the universe is getting bigger.

I still like to think of it more like the universe is getting less dense while retaining the same mass because it more accurately describes what is actually happening.

tommac
2009-May-07, 02:20 AM
A white hole would not be empty ...
The definition of a WH is a time reversal of a BH. So a BH is not empty neither is a white hole. As I stated in my other post the accelleration / decelleration is not reversible. A black hole accelerates stuff in the direction of the BH a WH accelerates ( decelerates ) stuff in the direction of the WH


Wouldn't a white hole be repulsive? I.E. the closer you get to it the more energy you would have to use to reach it. In the end you would never get to it?

Actually never mind. A white hole would be a complete absence of matter and energy. By that and our understanding of gravity it would not have a repulsive effect as the absence of matter != anti gravity.

So I'm still confused why you would think a white hole would have a gravitational well at all.

pzkpfw
2009-May-07, 02:46 AM
If the universe was infinite wouldnt we all be torn apart by ( an infinite amount of ) gravity?

Example: At the centre (of gravity of) the Earth, we are weightless due to being evenly surrounded by its' mass.

So I think in an infinite Universe (of reasonably uniform distribution), we'd be at the centre (like anything else would also be) and we'd feel an overall nothing.

We'd only feel Gravity from the specific things closer to us - like the Planet we are standing on.



Edit: remove musings that were probably ATM.

Hornblower
2009-May-07, 02:51 AM
If the universe was infinite wouldnt we all be torn apart by ( an infinite amount of ) gravity?
To the best of my knowledge, no.

01101001
2009-May-07, 03:13 AM
I meant entire universe not just the visible part

So, then, what is your definition of size? Is it the diameter of a sphere? Why a sphere?

Do you have some insight that the entire universe was ever even of finite size, let alone at some point smaller than the size of a golf ball?

tommac
2009-May-07, 05:28 PM
So, then, what is your definition of size? Is it the diameter of a sphere? Why a sphere?

Do you have some insight that the entire universe was ever even of finite size, let alone at some point smaller than the size of a golf ball?

I really dont believe this. But was working off of someone elses post, I think in ATM. Where the entire universe was smaller than a golf ball.

Gandalf223
2009-May-07, 05:52 PM
So are you saying that at t0 ( the beginning of time ) the universe was "perhaps a large fraction of its current size"?

Nope. Read my post.

I said that was the case at around t = 10^-32 seconds.

01101001
2009-May-07, 06:26 PM
I really dont believe this. But was working off of someone elses post, I think in ATM. Where the entire universe was smaller than a golf ball.

So you don't know what your initial question means?

OK. I hope you get an answer that pleases you.

tusenfem
2009-May-07, 09:13 PM
I really dont believe this. But was working off of someone elses post, I think in ATM. Where the entire universe was smaller than a golf ball.


tommac, I fail to see then why you ask the question. From the thread I see that, even after asking innumerable questions about the BB and BHs, you still have not learned anything. Maybe you should put some effort in understanding the answers that you get, and maybe you could read some real introductory physics books. And next to that, the title of this thread only has a tangential link to your opening message. If you don't believe this stuff from your OP, I think we can close this thread.