Big Bang and PreExisting Void?

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In summary, the concept of the Big Bang expanding into a preexisting void does not make sense as space(-time) itself is what was expanding, not just the matter in it. There is also the idea that a new universe could have been generated from a vacuum fluctuation and that space itself was created by a previous Big Bang. The existence of an infinite and eternal space as the absence of matter raises questions about the number of dimensions and the possibility of multiple universes coexisting in a void. However, this concept also raises difficult questions and cannot be proven or disproven.
  • #1
awktrc
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How do we know that the Big Bang did not expand into a preexisting void?

What is the justification for this knowledge/belief?
 
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  • #2
The BB didn't expand "into" anything (in the way you're suggesting). Space(-time) itself is what was expanding, not just the matter in it. It doesn't make sense to describe it as expanding "into" something.
 
  • #3
awktrc said:
How do we know that the Big Bang did not expand into a preexisting void?

What is the justification for this knowledge/belief?
If you examine what a universe would look like "from the outside", so to speak, it would look like a black hole. Because the new universe looks like a black hole from the outside, it is unable to expand into the pre-existing universe. But it has no trouble expanding from the perspective of somebody within the new universe.

That is, if a new universe was generated from a vacuum fluctuation in an existing universe, it would look like a microscopic black hole that came into existence for a moment, then rapidly evaporated away. One way of looking at it is that the space-time of the new universe "pinches off" from the old one, and almost instantly the new universe is all on its own, with no connection to where it came from.
 
  • #4
Painting on a canvas is a classical argument - suggesting matter must be superimposed over a preexisting 'space'. There is no valid theoretical or observational evidence supporting that premise.
 
  • #5
lets assume that it did expand into a preexisting space. Then where did that space come from? Another Big Bang? Did that Big Bang expand into a preexisting space?

At some point there had to be a Big Bang that created space itself.
 
  • #6
granpa said:
lets assume that it did expand into a preexisting space. Then where did that space come from? Another Big Bang? Did that Big Bang expand into a preexisting space?

At some point there had to be a Big Bang that created space itself.

If cold is the absence of heat, and dark is the absence of light, why can’t an infinite and eternal space be the absence of matter? To me asking the question where did space come from doesn’t make any more sense than asking where did dark or cold come from. There does not seem to be consensus on this forum as to whether space existed prior to or was created by the bb.

Okay…back to lurk mode for me.

Tom
 
  • #7
Chiclayo guy said:
If cold is the absence of heat, and dark is the absence of light, why can’t an infinite and eternal space be the absence of matter? To me asking the question where did space come from doesn’t make any more sense than asking where did dark or cold come from. There does not seem to be consensus on this forum as to whether space existed prior to or was created by the bb.

Okay…back to lurk mode for me.

Tom

infinite and eternal space of how many dimensions? 3? why not 1,826,548,356,657 dimensions?
 
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  • #8
And it still may safely be assumed that no information could 'pass' through the Big Bang event. i.e. No matter formation 'instructions' at any scale level, or anything else. Everything that took place after has just been random chance out of perhaps a near infinite range of possibilities?
 
  • #9
well, the big bang itself seems to over-ride a fundamental law in biology where spontaneous generation (eg- a universe [XD]) is impossible, unless being that there can be apparently be another creating force to do it.

Also in statement, having an infante number of dementions seems to sasify this as well, as in an infante number of universes may have existed previously. Furthering that, with an infante number of dementions, there could be an infante number of different results in each of the other universes created from other "big bangs" occurring in other dementions. Furthering that, having an infante number of dementions with universes ending to an infantle variable rate they'd be destroyied/created.

..the big-bang was technically random?Or can alternate dementions interact? For example, if universe "A" was being destroyed. While inside universe "A" another random universe was being created. (having an infante number of detementions within a demention) Due to the fact a universe may be random. Now, this new "internal" universe, universe "B" was expanding and universe "A" was being destrioed. Apon Universe "A"'s destruction, universe "B" was able to form fully. Any such that was aware of universe "B" was able to excape to it. And any such unaware of universe "B" was destroied.

(why does this sound like economics, cancer, and the molting of an animals skin...?)

Now in this example, there is only now universe "B" but all the such lone in the destruction of universe "A", does this mean the remniants create a NEW universe? Kinda like the "seeds" of a tree that was chopped down.

o_O... (why does this sound religious, philosophical, and strangely like the book "the lord of the flies"...?)And due to the fact these lone such are in hyper space, they can expand without any other universe holding them back by those universes forces. 0_o...
 
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  • #10
zhermes said:
The BB didn't expand "into" anything (in the way you're suggesting). Space(-time) itself is what was expanding, not just the matter in it. It doesn't make sense to describe it as expanding "into" something.

Getting back to this for a moment, could it not be that a void surrounded the BB which was not comprised of spacetime but rather was a simple void which had no characteristics or properties? Could multiple universes be "housed", surrounded in a void soup of sorts? It outwardly seems to me that the existence of a void of this sort could never be proven or disproven.

I love this thread, very interesting!
 
  • #11
In such case there should be a border between 'ordinary' and how you call it 'simple' void. You would face many difficult questions like:

Why both types of void have the same number of dimensions?
What happens in places where ordinary space is curved?
What is a border between 2 types of voids?
Is it sharp or smooth?
What happens to an object or particle going thru the edge?
In any case, go thru all theories (QM, EM, Gravity) and incorporate such type of object there.

Purely hypotetically, if our spacetime could have edges in space, such edges would emit enourmous quantities of hawking radiation because of the pair production, when 1 component of the pair dissapears behind the edge. Contrary to Black Holes, that radiation is not redshifted by gravity and is EXTREMELY intense. Very soon it curves space because of its enourmous energy density and creates real black hole with a 'normal' event horizon :)
 
  • #12
awktrc said:
How do we know that the Big Bang did not expand into a preexisting void?

We don't.

We can however say that the observations of the universe are inconsistent with any void existing any part of the universe we can observe or which influences the behavior of anything that we can observe.
 
  • #13
Chronos said:
Painting on a canvas is a classical argument - suggesting matter must be superimposed over a preexisting 'space'. There is no valid theoretical or observational evidence supporting that premise.

Let me rephase that to something stronger. The observations say that for the parts of the universe we have any data of, that the universe is not spreading into a void. If the universe was spreading into a void, you'd see the effects of the void. You don't.
 
  • #14
justwondering said:
And it still may safely be assumed that no information could 'pass' through the Big Bang event.

Not true. Anytime someone "assumes" something, you should ask why we are assuming that.

Some of the current work in cosmology is to work on models of what the universe might of looked like before cosmic inflation happened and to see if any of the "pre-inflation" universe could have any effect on observable things like the CMB power spectrum.

This is important because relating theory to observations is what science is about.
 
  • #15
Dmitry67, thanks for your convincing reply, this stuff makes my brain hurt after 74 years of experience with edges and boundaries. One final idiot question:

Assuming the existence of multiple universes for a moment, it appears that they cannot be separated from our universe by any sort of boundary, like a border fence. Do they then co-exist within our own universe, separated from us by different dimensions or time? If our universe is infinite/flat, where else could they be? (Brain hurts again.)
 
  • #16
Oldfart, our universes our 4 dimensional, so they can coexist in higher dimensional space without any intersections. That hypotetical super-space is called BULK. However, let's wait for TOE to get clearer picture.

For the classification of types Universes in Multiverse (I, II, II and IV) google Max Tegmark Mathematical Universe Hypotesis.
 
  • #17
Dmitry67 said:
Oldfart, our universes our 4 dimensional, so they can coexist in higher dimensional space without any intersections. That hypotetical super-space is called BULK. However, let's wait for TOE to get clearer picture.

For the classification of types Universes in Multiverse (I, II, II and IV) google Max Tegmark Mathematical Universe Hypotesis.

Thanks again, Dmitry67! I checked some of Max's stuff, did not understand it, but then, what's new? Is there a book or two out there that sort of gently leads a layman by the hand through our infinite, expanding universe? You can see by inquiries in this thread that some of us have conceptual problems, need help. (Though I fear that the math involved may greatly limit communication between us.)
 
  • #18
twofish-quant said:
If the universe was spreading into a void, you'd see the effects of the void. You don't.

What effects would a void have? Wouldn't said void, by definition, be empty of anything that would cause an effect that could be detected?
 
  • #19
There is a word they use in physics for anything that is entirely uninteractive - nonexistent.
 
  • #20
Chronos said:
There is a word they use in physics for anything that is entirely uninteractive - nonexistent.

Dang, Chronos, I've spent at least ten minutes trying to figure out whether your statement is helpful or simple sarcasm...

OK, let's see if I've got this figured out. Assuming the universe is flat/infinite, it didn't just get infinite one day but always has been, even at the start of the BB, when it was, let's say, the size of a pea. Correct? OK, us folks that have this mental picture of the BB expanding into a void are mentally sitting in this void, outside the BB, and watching this thingy expand, and thinking yep, it's expanding into a void, alright! But this cannot be a correct way of thinking, as this would mean placing the observer beyond infinity. The observer, and the void for that matter, cannot possibly exist beyond infinity. Correct?

Having made the void impossible, I am now left with only the minor mental problem of stuffing an infinite universe into a pea...
 
  • #21
It makes more sense if you picture expansion creating its own space as it evolves, and that space is created in the vast gulfs between galactic clusters. Empty space is endowed with a peculiar property called dark energy, and this dark energy is accelerating the expansion of the universe.
 
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  • #22
Looking at this thread, I see that the OP has asked a question, 20 answers have been given, the OP hasn't posted again, and virtually all of the answers are not answers to the OP's question. The OP asked, "how do we know X?," and virtually all the answers are "X is true! X is true! Let me explain X to you!"

twofish-quant said:
Let me rephase that to something stronger. The observations say that for the parts of the universe we have any data of, that the universe is not spreading into a void. If the universe was spreading into a void, you'd see the effects of the void. You don't.

Twofish-quant has tried to answer the OP's actual question here. Hurrah!

I'm not completely satisfied with twofish-quant's answer, however. Maybe it could be improved upon.

Our observations can only reach out to a certain distance. If all we know is that we don't see a surrounding void, that doesn't seem like a very strong argument to me, since maybe we just don't see the surrounding void because it's too far away.

Here is a possible alternative approach.

(1) General relativity has passed a variety of experimental tests, so we think it's probably pretty accurate. (2) We observe that the redshifts of distant supernovae follow a certain dependence on their distance from us. (3) We also observe that the cosmic microwave background has fluctuations on certain angular scales.

Smart people have tried very hard to find a model that fits 1, 2, and 3. All they've managed to come up with is a particular model in which there is no preexisting void. In fact, the observations fit that model extremely well. On the other hand, nobody has ever found a model *with* a preexisting void that fits 1, 2, and 3. That makes us suspect that there is no preexisting void.

Another line of attack is that if we only assume 1 above, then the Hawking singularity theorem http://en.wikipedia.org/wiki/Penrose–Hawking_singularity_theorems , plus some relatively crude observations of the present state of the universe, tells us there must have been a singularity in our past. Such a singularity, as described by GR, has features that are incompatible with the idea of an explosion in a preexisting spacetime. In particular, if GR is correct, then timelike world-lines can't be extended backward through that singularity.
 
  • #23
Chronos said:
It makes more sense if you picture expansion creating its own space as it evolves, and that space is created in the vast gulfs between galactic clusters. Empty space is endowed with a peculiar property called dark energy, and this dark energy is accelerating the expansion of the universe.

OK, maybe your explanation "makes more sense", but you are running ahead of me. Is there anything in my previous explanation that is incorrect? And why does your explanation make more sense, it doesn't seem to relate to the "void" issue. Duhh...

But thanks for getting back!
 
  • #24
bcrowell said:
Our observations can only reach out to a certain distance. If all we know is that we don't see a surrounding void, that doesn't seem like a very strong argument to me, since maybe we just don't see the surrounding void because it's too far away.

Quite true. But what we can say is that there are no voids within *X* billion light years of the earth, right now I think the limit of *X* is 60 billion light years of the earth. There could be voids 1.2 trillion light years from year, or not...

On the other hand, nobody has ever found a model *with* a preexisting void that fits 1, 2, and 3. That makes us suspect that there is no preexisting void.

Who is "us"? All I can say is that with our current knowledge of the universe, there are no detectable anisotropies and inhomogeneities within 60 billion light years. There could very will be massive voids 1.2 trillion years out.

I can also say that when I do my GR calculations I *assume* that there are no voids at all, because it makes the math easier.

In particular, if GR is correct, then timelike world-lines can't be extended backward through that singularity.

The trouble is that it is known that GR is wrong once you get to Planck's length.
 
  • #25
twofish-quant said:
Who is "us"? All I can say is that with our current knowledge of the universe, there are no detectable anisotropies and inhomogeneities within 60 billion light years. There could very will be massive voids 1.2 trillion years out.
I think we should distinguish logically between a large but finite void and the case where there is an infinite, preexisting, asymptotically flat void. The latter is really what the OP was asking about.

twofish-quant said:
I can also say that when I do my GR calculations I *assume* that there are no voids at all, because it makes the math easier.
It is certainly easier to do calculations with an assumption of homogeneity and isotropy, but it's also impossible to cut and paste a Big Bang singularity into an infinite, preexisting, asymptotically flat void. A BB singularity, which we know exists because of the Hawking singularity theorem, has geodesic incompleteness, so it can't arise out of a preexisting void.

twofish-quant said:
The trouble is that it is known that GR is wrong once you get to Planck's length.
True. Everything I'm saying is in the context of classical GR.
 
  • #26
If the universe is surrounded by an infinite void, it is difficult to explain why the cmb intensity is identical in every direction.
 
  • #27
Chronos said:
If the universe is surrounded by an infinite void, it is difficult to explain why the cmb intensity is identical in every direction.

Interesting point. Although our planet could of course just happen to be located at a special center of symmetry, or the void could be beyond the current horizon as seen from earth.
 
  • #28
Chronos said:
If the universe is surrounded by an infinite void, it is difficult to explain why the cmb intensity is identical in every direction.

Imagine you have two BigBangs in the preexisting void, separated by a distance greater than the actual size of our universe. Before the two BB frontiers (cmb) reach each other, you have no effect for someone that is inside each own universe.
And the cmb intensity is nor identical in every direction. Could this fluctuations in the cmbr been caused by other universes created by other BB?
Maybe our expanding universe just needs more time until it bumps with another one.. in this preexisting void. I like the idea.
 
  • #29
I still need help with this -- anyone?

IF our universe is infinite, can it be surrounded by a void (beyond infinity??). Or is that OK, since an absolute void is, after all, um, nothing?
 
  • #30
nunogirao said:
Imagine you have two BigBangs in the preexisting void, separated by a distance greater than the actual size of our universe.
This doesn't actually make a difference. The thing is, space-time is not some absolute thing, so even if you have two big bang events born within some other space-time separated by some distance, those two big bang events still can never interact in any way, shape, or form. The new space is generated within each individual event, and cannot effect either the parent universe or anything else.

One way to see this is to just look at the Schwarzschild radius of a black hole with the mass of our observable universe. It turns out that that Schwarzschild radius is larger than our observable universe, which in turn means that if there is an edge to our universe, from the outside it must necessarily look like a black hole.

So we have a picture where when a new universe is formed, it forms within the parent universe as a microscopic black hole which rapidly evaporates, forever disconnecting the new universe from the parent universe, leaving no way for the two to interact whatsoever. The space-time of the new universe, almost immediately after the new universe is formed, is entirely self-contained and cannot interact with any other universe.
 
  • #31
Chalnoth said:
This doesn't actually make a difference. The thing is, space-time is not some absolute thing, so even if you have two big bang events born within some other space-time separated by some distance, those two big bang events still can never interact in any way, shape, or form. The new space is generated within each individual event, and cannot effect either the parent universe or anything else.

I don't know if the space-time was created in the BB or if it is something that ever existed (and there we go to the «when/why» it was created).
So, is the void just the space-time fabric, where BBs occour?
And, could it be possible that different types of universes (with different rules) populate the same void? Could a «neutrino type» universe exist that just transverse our universe, without influencing it?
 
  • #32
nunogirao said:
I don't know if the space-time was created in the BB or if it is something that ever existed (and there we go to the «when/why» it was created).
However it started, space most definitely expanded. It may have started from a pre-existing space-time, as I mentioned. But entirely new space is produced as the universe expands. The expansion of the new universe cannot ever possibly be observed in the old universe.

nunogirao said:
And, could it be possible that different types of universes (with different rules) populate the same void?
From what we know of high energy physics today, it definitely appears that different regions of space-time, both within a universe and between them, may well have different low-energy laws of physics. We really can't say much at all about the extent of this variation just yet. For now, the only variation from place to place that we have at least some confidence of is the electroweak symmetry breaking event, which appears to have a particular parameter that is random and varies from place to place (as in it is likely different some place far from our observable universe, but is the same everywhere we can see).

nunogirao said:
Could a «neutrino type» universe exist that just transverse our universe, without influencing it?
Well, unless you want to talk about higher-dimensional theories like string theory, it just isn't sensible to talk about another universe existing transverse to our own. In General Relativity, our space-time is self-contained and cannot overlap with any other universe.

However, in string theory, the "true" universe has 10 space-time dimensions (11 in M-theory), and we might exist on a brane with 4 space-time dimensions, which could, in principle, be close to another 4-dimensional brane, rather in the same way that two sheets of paper can be placed close to one another. Most forces are stuck on the brane, so that we could not observe the other brane through them, but gravitational interactions always remain, and we could interact with this other universe through gravity.
 
  • #33
awktrc said:
How do we know that the Big Bang did not expand into a preexisting void?

What is the justification for this knowledge/belief?

We don't - unless we are creatures that are simply satisfied to collect data, some degree of speculation cannot be avoided (Eddington). And when it comes to beginnings, there is no dearth of speculative theories. Most of these are based on what we observe within the confines of the Hubble sphere centered upon our observational position on Earth - but there is much evidence that leads to the notion that the actual universe of matter in the form of particles is at least 3 times the Hubble scale - this in part due to an extrapolation of redshift data that shows nebula receding from one another at velocities in excess of c.

I personally have come to speculate upon a pure de Sitter exponentally expanding background space - with neither beginning in time nor space - an interesting twist on the big bang as an initial expansion is a symmetry breaking withing some small volume of the de Sitter background space leading to an abrupt contraction of that volume into a dense volume of proto particles - followed by later expansion to its present limit defined by a de Sitter horizon.

When it comes to beginnings, some are better than others - but there is not much possibility of being proved wrong even if your ideas are as far out as mine.
 
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  • #34
awktrc said:
How do we know that the Big Bang did not expand into a preexisting void?

What is the justification for this knowledge/belief?

If you go back to the original source "Relativity, Gravitation, and World Structure" you will see that Milne's model described a Big Bang expanding into a preexisting void. He reassured the reader that nothing could ever get in from outside because the outside edge of the explosion consists (now and forever) of a surface with infinite density traveling at the speed of light.

In fact it only comforts me a little, because if there were another universe in the same infinite void, it's density in its outer shell would also be infinite, and moving toward us at the speed of light. The good news is, if something hits you at the speed of light, you won't ever see it coming until it gets there.

As far as the justification for rejecting the Milne model, I have been trying to figure that out as well. So far, all I've found is that they already have whatever they want with the standard model, and they have read so much misinformation about the Milne model that they find it ludicrous. In fact, you can't even so much as print up the density function for the Milne model on Wikipedia because it is "original research." I imagine, if you quote anything by Milne and put it up under the article for Milne's Model, it will be taken down, because Wikipedia relies on "Reliable Secondary Sources." Unfortunately, the few remaining copies of Relativity Gravitation and World Structure are probably to be burned, and the idea, whether correct or not, will be forever lost.
 
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  • #35
Chronos said:
If the universe is surrounded by an infinite void, it is difficult to explain why the cmb intensity is identical in every direction.

If WE, and everything we see came from the same point and the same time, then wouldn't it make sense to expect it all to look the same in every direction?
 
<h2>1. What is the Big Bang theory?</h2><p>The Big Bang theory is the prevailing scientific explanation for the origin of the universe. It proposes that the universe began as a singularity, a point of infinite density and temperature, and has been expanding and cooling ever since.</p><h2>2. What caused the Big Bang?</h2><p>The exact cause of the Big Bang is still unknown and is a topic of ongoing research and debate. Some theories suggest that it was triggered by a quantum fluctuation, while others propose the existence of a previous universe that collapsed and gave rise to the Big Bang.</p><h2>3. What is the evidence for the Big Bang?</h2><p>There are several pieces of evidence that support the Big Bang theory, including the cosmic microwave background radiation, the abundance of light elements, and the redshift of galaxies. These observations are consistent with the predictions of the Big Bang model.</p><h2>4. What is the PreExisting Void?</h2><p>The PreExisting Void, also known as the cosmic void, is a vast region of space that appears to contain very few galaxies and other matter. It is thought to have formed during the early stages of the universe's expansion and may have played a role in shaping the large-scale structure of the universe.</p><h2>5. How does the PreExisting Void relate to the Big Bang?</h2><p>The PreExisting Void is not directly related to the Big Bang, but it is thought to have formed as a result of the rapid expansion that occurred during the early stages of the universe. It is also believed to have influenced the distribution of matter and galaxies in the universe, providing valuable insights into the processes that shaped our universe.</p>

1. What is the Big Bang theory?

The Big Bang theory is the prevailing scientific explanation for the origin of the universe. It proposes that the universe began as a singularity, a point of infinite density and temperature, and has been expanding and cooling ever since.

2. What caused the Big Bang?

The exact cause of the Big Bang is still unknown and is a topic of ongoing research and debate. Some theories suggest that it was triggered by a quantum fluctuation, while others propose the existence of a previous universe that collapsed and gave rise to the Big Bang.

3. What is the evidence for the Big Bang?

There are several pieces of evidence that support the Big Bang theory, including the cosmic microwave background radiation, the abundance of light elements, and the redshift of galaxies. These observations are consistent with the predictions of the Big Bang model.

4. What is the PreExisting Void?

The PreExisting Void, also known as the cosmic void, is a vast region of space that appears to contain very few galaxies and other matter. It is thought to have formed during the early stages of the universe's expansion and may have played a role in shaping the large-scale structure of the universe.

5. How does the PreExisting Void relate to the Big Bang?

The PreExisting Void is not directly related to the Big Bang, but it is thought to have formed as a result of the rapid expansion that occurred during the early stages of the universe. It is also believed to have influenced the distribution of matter and galaxies in the universe, providing valuable insights into the processes that shaped our universe.

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