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Subject: S is for science, so a Big Bang question for you-all rss

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Steve
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Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

.......................................................................

2nd question.

What is the electrical resistance of empty space that contains a few charged particles per cubic meter?

Is it zero or is it infinite? Or, is it some non-zero number?

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Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?




It's not an expansion of matter through space but an expansion of space itself.
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Stirlingmoomoo wrote:
Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?




It's not an expansion of matter through space but an expansion of space itself.

What evidence is there that space expanded? Has anyone seen it do that recently?

Edit, forgot to say Thank you.

 
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Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?


Drop a little piece of ferrous metal on the table. Try to lift it with a very small magnet. Which is stronger, the gravity mediated by the entire planet or the magnetism?

Gravity is very weak compared to other forces.


Quote:
What is the electrical resistance of empty space that contains a few charged particles per cubic meter?

Is it zero or is it infinite?

Both, when there's nothing there

but the few charged particles stop it being empty, at which point:
Quote:
is it some non-zero number?
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Steve1501 wrote:
then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

The density was uniform everywhere so there was no point that it would collapse to.
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Steve1501 wrote:
What evidence is there that space expanded? Has anyone seen it do that recently?

we see that the farther away a galaxy is from us, the faster it is receding from us, which scientists interpret as the expansion of the universe.
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I have no answers, only more questions, I hope you don't mind:

What was before the Big Bang?
The ever-expanding universe might all scrunch up again into this golfball, that is a theory I heard about years ago, is it still valid?
And what then?
What is "behind" or "around" the universe?
Are there multiple parallel universes?

Sorry, I don't mean to derail the thread.
In case you think I do, just ignore me.
 
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being wrote:
What was before the Big Bang?

nothing. that's not a very good answer though...

Quote:
The ever-expanding universe might all scrunch up again into this golfball, that is a theory I heard about years ago, is it still valid?
And what then?

nope, I think the current view is that the universe will keep expanding and eventually we will have a "heat death"

Quote:
What is "behind" or "around" the universe?
Are there multiple parallel universes?

there's a multiverse theory that sort of says our universe could be like a bubble in a foam, with other bubbles around us being other universes. that's not really testable though
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in the dark universe - gravity is strong and repelled the uniformly weak gravity in our universe away from it.

Or god sneezed and forgot to bring his hanky whistle
 
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being wrote:
I have no answers, only more questions, I hope you don't mind:

What was before the Big Bang?


Doesn't make sense. There was no before. Spacetime did not exist. However people like Stephen Hawking and Neil Turok use a mathematical concept called imaginary time and model what is called an instanton which kinds of bursts and forms the bang. Others have put forward brane-collision in a kind of superspace as being the causative agent.

Quote:

The ever-expanding universe might all scrunch up again into this golfball, that is a theory I heard about years ago, is it still valid?


The Big Crunch is seen as pretty unlikely although there are a few who still think that the crunch might be a valid end-state. There are probably a very small number who believe in a bang-crunch-bang cycle too.

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What is "behind" or "around" the universe?


Nothing. Or rather the question doesn't really make sense. The universe is expanding but it isn't expanding into anything. Although the brane theorists have their idea of a superspace which they call the bulk.

Quote:
Are there multiple parallel universes?


Yes, no, maybe - depends on who you talk to and what you mean by multiple parallel universes.

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Marshall P.
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Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?


whatever the universe was at the moment of the big bang it didn't consist of matter and energy as we observe it now (i.e. it wasn't made of protons and photons). It was probably within a quantum fluctuation of being nothing altogether.

All of the matter and radiation that we count up as having energy in the current age of our universe is offset by the negative gravitational potential energy of the expanding universe itself.

In other words, the universe is still really nothing at all. It's just a peculiar form of nothing where a bunch of positive energy is offset by a bunch of negative energy.

While this is a satisfying answer for why there is something rather than nothing (turns out there really IS nothing). It's not satisfying, and demands explanation, for why there should be this particular arrangement of "nothing" (i.e. a bunch of condensed matter and radiation in an expanding spacetime).

There's not really an answer for why spacetime inflated. And for why the positive component of energy in the universe manifests itself as the family of particles described by the standard model. But there appears to be nothing inconsistent of unallowed by it having done so.
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Steve
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jmilum wrote:
Steve1501 wrote:
then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

The density was uniform everywhere so there was no point that it would collapse to.

1st, no it was not totally uniform. If it had been then it would still be uniform now, right? There must have been some tiny differences in "density". {Note: I'm old so I don't do "scare Quotes". When you read my posts and you see a word or phrase in quotes, I'm either quoting someone or I'm saying "this word or phrase is not quite right but close to what I mean," or like here I'm telling you "this phrase goes together."]

2nd, are you saying that the big band universe is infinite in extent and always was, but at one time was as small as a golf ball? If it is finite in size now and expanding, what [space?] is it expanding into?

 
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Steve
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mdp4828 wrote:
Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?


whatever the universe was at the moment of the big bang it didn't consist of matter and energy as we observe it now (i.e. it wasn't made of protons and photons). It was probably within a quantum fluctuation of being nothing altogether.

All of the matter and radiation that we count up as having energy in the current age of our universe is offset by the negative gravitational potential energy of the expanding universe itself.

In other words, the universe is still really nothing at all. It's just a peculiar form of nothing where a bunch of positive energy is offset by a bunch of negative energy.

While this is a satisfying answer for why there is something rather than nothing (turns out there really IS nothing). It's not satisfying, and demands explanation, for why there should be this particular arrangement of "nothing" (i.e. a bunch of condensed matter and radiation in an expanding spacetime).

There's not really an answer for why spacetime inflated. And for why the positive component of energy in the universe manifests itself as the family of particles described by the standard model. But there appears to be nothing inconsistent of unallowed by it having done so.

Vveeerrryy interesting, I'll have to ponder this some.

 
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Steve1501 wrote:
Seriously.

If in the 1st micro second after the Big Bang all the matter and energy of our current universe was in a volume equal to a golf ball,

then how could it expand as an explosion?

1. Big bang is a misnomer; there was no explosion, just expansion. Bear in mind that the universe has literally nothing outside it-- including no vacuum. By expanding the universe lowers local energy density and thereby increases total entropy.
Quote:
Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

No. Relative to any observer at any point in the universe, the observer would see him- or herself as at the center with everything all about him moving. The movement would be in all directions but the observer would see it has predominately outward from his or her perspective. Gravity is relatively weak and would not overcome that outward pressure especially since the rate of outward expansion would only be continuously increasing. To contract inwards, the rate of expansion would have to decrease to zero at some point.
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.......................................................................

2nd question.

What is the electrical resistance of empty space that contains a few charged particles per cubic meter?

Is it zero or is it infinite? Or, is it some non-zero number?

Resistance relative to what? Do you mean what is the permittivity of free space? Besides, the universe is electrostatically neutral on the whole. So what has this to do with big bang anyway, even if the question were refined to make sense?
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Steve1501 wrote:
jmilum wrote:
Steve1501 wrote:
then how could it expand as an explosion? Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

The density was uniform everywhere so there was no point that it would collapse to.

1st, no it was not totally uniform. If it had been then it would still be uniform now, right? There must have been some tiny differences in "density". {Note: I'm old so I don't do "scare Quotes". When you read my posts and you see a word or phrase in quotes, I'm either quoting someone or I'm saying "this word or phrase is not quite right but close to what I mean," or like here I'm telling you "this phrase goes together."]

2nd, are you saying that the big band universe is infinite in extent and always was, but at one time was as small as a golf ball? If it is finite in size now and expanding, what [space?] is it expanding into?


It isn't expanding into a space. The expanding universe is everything.
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Marshall P.
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being wrote:
I have no answers, only more questions, I hope you don't mind:

What was before the Big Bang?


There is no answer right now. You will get some who say there was no "before" because time itself began in the big bang. You will get other physicists who say that time is symmetrical (i.e. extending infinitely both to the future and to the past) in which case there was something before the big bang but it may be impossible to know what it was since the big bang was a moment of maximum energy and zero information. There probably was no way for it to "record" what happened before and thus no way for us to know.

Quote:
The ever-expanding universe might all scrunch up again into this golfball, that is a theory I heard about years ago, is it still valid?]


Physically yes, it's a valid theory. Empirically, however, it looks instead like our universe is destined to expand forever at an accelerating rate. "Heat death" as jmilum said.

Quote:

What is "behind" or "around" the universe?


Complicated question. Because the expansion of spacetime was faster than the speed of light, there is a horizon beyond which we cannot see. Call this the observable universe. The observable universe is about 92 billion light years in diameter right now (even though we only see what it looked like about 12 billion years ago due to the finite speed of light).

Beyond that diameter is almost certainly more of the same. A lot more probably. We just won't ever see it. But it probably is made up of the same stuff that we are made of, and following the same laws of physics.

Beyond that and we're into speculation. It could be that the Universe is closed and that one edge connects back around to the opposite edge and there is nothing beyond it just like there is no edge of the earth. Or the universe could be unbounded and infinite in extent.

In either case there can be other, multiple universes besides ours.


Quote:
Are there multiple parallel universes?


Maybe. I think this is a place where some scientists go further than I would like to go. Some physicists think a multiverse is necessary and therefore exists. I think of this question as probably unanswerable.

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whac3 wrote:

Quote:
Why would it not contract into a point under all that gravity and become or remain a "Black Hole"?

No. Relative to any observer at any point in the universe, the observer would see him- or herself as at the center with everything all about him moving. The movement would be in all directions but the observer would see it has predominately outward from his or her perspective. Gravity is relatively weak and would not overcome that outward pressure especially since the rate of outward expansion would only be continuously increasing. To contract inwards, the rate of expansion would have to decrease to zero at some point.


Have you read Kaloper and Padilla? They seem to think that a collapse is possible based on their vacuum energy sequestering work.

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114...
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mdp4828 wrote:

Quote:
The ever-expanding universe might all scrunch up again into this golfball, that is a theory I heard about years ago, is it still valid?]


Physically yes, it's a valid theory. Empirically, however, it looks instead like our universe is destined to expand forever at an accelerating rate. "Heat death" as jmilum said.


The Big Rip is another theory about the end of the universe which a number of people seem to prefer.
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Steve1501 wrote:

What evidence is there that space expanded? Has anyone seen it do that recently?

Edit, forgot to say Thank you.


1. Yes, it happens all the time everywhere quite literally.
2. The evidence is somewhat technical to explain. Macroscopically it typically involve Type II supernovae. These are a type of the astronomical body whose position relative to us we can accurately measure. We can see that even though everything along the path to the Type II supernova including it and us appear to be stationary, the relative distances involved are increasing. Yet they are not pushing into stuff round them.

Microscopically there are various evidences involving quantum pressure.
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I read once that a scientist who was around as the 1st stars formed would not have been able to predict that life would evolve for instance. After all, he hadn't even imagined chemistry or seen liquid water yet.

What he was saying is that just knowing what is known at a point in time should not allow one to extrapolate it into the far, far distant future.

So, I think that extrapolating what we think we know now into the future a 100 Billion years from now is pointless. There is almost certainly something or some new "force" that comes along and changes everything.

Dinosaurs may have thought that they had the world by the tail. Then this really big rock fell out of the sky.

 
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andyl;

The WMAP data seems though to indicate that in the cosmological sense the universe is flat, not closed. Still it remains theoretically an open research question.

EDIT:
I've not read that research though.
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Steve1501 wrote:
I read once that a scientist who was around as the 1st stars formed would not have been able to predict that life would evolve for instance. After all, he hadn't even imagined chemistry or seen liquid water yet.

What he was saying is that just knowing what is known at a point in time should not allow one to extrapolate it into the far, far distant future.

So, I think that extrapolating what we think we know now into the future a 100 Billion years from now is pointless. There is almost certainly something or some new "force" that comes along and changes everything.

Dinosaurs may have thought that they had the world by the tail. Then this really big rock fell out of the sky.


Nobody's talking about the far distant future.
 
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Steve1501 wrote:

1st, no it was not totally uniform. If it had been then it would still be uniform now, right?…

The universe at a large scale is very well homogeneous and isotropic. Namely it is still uniform.
 
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whac3 wrote:
Steve1501 wrote:

1st, no it was not totally uniform. If it had been then it would still be uniform now, right?…

The universe at a large scale is very well homogeneous and isotropic. Namely it is still uniform.

It doesn't look that way to me. Maybe I'm too close to the tiger to see its stripes.

I'm told that there are clusters of galaxies and maybe even clusters of clusters of galaxies. Or, strings of clusters of galaxies. This doesn't seem "uniform" to me.

 
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whac3 wrote:
Steve1501 wrote:
I read once that a scientist who was around as the 1st stars formed would not have been able to predict that life would evolve for instance. After all, he hadn't even imagined chemistry or seen liquid water yet.

What he was saying is that just knowing what is known at a point in time should not allow one to extrapolate it into the far, far distant future.

So, I think that extrapolating what we think we know now into the future a 100 Billion years from now is pointless. There is almost certainly something or some new "force" that comes along and changes everything.

Dinosaurs may have thought that they had the world by the tail. Then this really big rock fell out of the sky.


Nobody's talking about the far distant future.

Wrong.

I'm sure that at least jmilum did. He said we were heading to a "heat death".
. . Didn't I quote him even, I thought I had.

 
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