Multiple big bangs in one continuum - Question

[Pizza]

I have fond almost the same question here with some answers. Anyhow, I am not satisfied with the answers, or couldn't understand them well. Beside that, I would formulate the question a little bit different. Unfortunately the thread is already closed (from 2012).

Provided there is only one Universe, one Continuum. With an Euclidean space, flat and infinite just as a mathematical feature (lets say only content matters physically). Our Big Bang happened, not just an explosion, but except the creation of space and time - and we are able to observe our visible universe today. Is it imaginable, just imaginable, that beyond that are other Big Bangs, from time to time, many? Just too far away for any interaction noticeable up to our horizon, until now?

And more - leading to a new question - if they are all expanding like our own (assuming all known physical laws are identical, notabene one continuum, no multiverse scenarios), overlapping regions will occur. Some regions of space will see expansions from many directions and therefore this would be locally kind of a contraction - and leading to a new Big Bang, maybe. If a really giant black hole may ever lead to a new Big Bang, OK that's fantasy.

The new question would be, is it imaginable that at a certain amount of too much mass a black hole "explode"? But that's worth for an own thread, probably existing many already. As far as I know, that's impossible, but who knows? Would appreciate some opinions.

Sorry if my English is strange, am not a native speaker.

 

[DaveC426913]

The Big Bang did not occur "in" an expanse of spacetime; it created spacetime. The entire universe - spacetime and all - was once smaller than an atom. So there is no other expanse in which other Big Bangs could occur.

 

[Pizza]

I think, I understand what you mean, but what if space and time weren't created there, existing already? Without implications to spacetime, this could be and stay as it is. I am using the term universe as something a little larger or different than usual, as the thing that includes everything. Of course, I know, that the usual meaning of the universe is exactly that, what came out of the big bang. I puzzle how to express what I mean, because I am using universe as the original short definition, but the same word is used for the standard theory, with a little bit longer definition. Marcus noticed that the language is a challenge anyway, if I remember well - read this today.

 

[DaveC426913]

I understand what you mean, but what if space and time weren't created there, existing already? Without implications to spacetime, this could be and stay as it is. I am using the term universe as something a little larger or different than usual, as the thing that includes everything. Of course, I know, that the usual meaning of the universe is exactly that, what came out of the big bang. I puzzle how to express what I mean, because I am using universe as the original short definition, but the same word is used for the standard theory, with a little bit longer definition. Marcus noticed that the language is a challenge anyway, if I remember well - read this today.

You are speculating that there was spacetime beyond the universe as we know it, and that it was in existence when the Big Bang occurred.

Unfortunately, that is not part of the standard cosmological model, and Physics Forum is not the place for such speculation.

 

[Pizza]

Ah, okay. Sorry, that was just a question. I am new here, probably didn't read all the small print. Thank you for your answers.

 

[PeterDonis]

Is it imaginable, just imaginable, that beyond that are other Big Bangs, from time to time, many? Just too far away for any interaction noticeable up to our horizon, until now?

There are inflationary models of cosmology (they are usually called "eternal inflation" models) where something like this is happening, but it still doesn't work the way you are describing. Each "Bang" in an eternal inflation model creates its own spacetime, as DaveC says, so there is no possibility of interaction between the different spacetimes created by different inflationary "Bangs".

 

[PeterDonis]

The new question would be, is it imaginable that at a certain amount of too much mass a black hole "explode"? But that's worth for an own thread, probably existing many already.

Yes, that question would need a separate thread (but the short answer is "no").

 

[Smattering]

The Big Bang did not occur "in" an expanse of spacetime; it created spacetime. The entire universe - spacetime and all - was once smaller than an atom. So there is no other expanse in which other Big Bangs could occur.

Can we really be sure that it was smaller than an atom? In another thread, I was told that the GR based models are not really thought to be applicable at arbitrary high energy levels. And as we only know the size of our Hubble volume, compressing the whole universe into the size of an atom might in fact lead to arbitrary high energy levels, right?

 

[phinds]

Can we really be sure that it was smaller than an atom? In another thread, I was told that the GR based models are not really thought to be applicable at arbitrary high energy levels. And as we only know the size of our Hubble volume, compressing the whole universe into the size of an atom might in fact lead to arbitrary high energy levels, right?

I agree w/ you. I think @DaveC426913 is off on this one. The universe might be infinite in which case it was always infinite but in any case I am not aware of any theories that say it was ever as small as an atom. The OBSERVABLE universe was tiny at the beginning but I don't think even it was as small as an atom.

 

[PeterDonis]

Can we really be sure that it was smaller than an atom?

What that really means is that our observable universe was once smaller than an atom. We can't assign a "size" to the universe as a whole; according to our best current model, our universe is spatially infinite, and even if it is actually finite, it has to be so much larger than the observable universe that we can't tell that it isn't spatially infinite, at least not with our current accuracy of measurement.

 

[Pizza]

There are inflationary models of cosmology (they are usually called "eternal inflation" models) where something like this is happening, but it still doesn't work the way you are describing. Each "Bang" in an eternal inflation model creates its own spacetime, as DaveC says, so there is no possibility of interaction between the different spacetimes created by different inflationary "Bangs".

Thanks for the hint "eternal inflation", very interesting:
"But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously. Alan Guth [7]"
Source
Solely what does multiverse mean, as you mentioned, not what I described. I thought that my suggestion is so simple, that ... I don't know. Maybe too easy, should be complicated, I don't know.
Cheers.

 

[PeterDonis]

The OBSERVABLE universe was tiny at the beginning but I don't think even it was as small as an atom.

Yes, it was. Fitting the observable universe into the volume of an atom corresponds to a density of around $10^{26}$ times that of water, which was the density of the universe at around the time of the electroweak phase transition. This is well within the regime that is covered by the standard model of cosmology.

 

[DaveC426913]

Yes, it was. Fitting the observable universe into the volume of an atom corresponds to a density of around $10^{26}$ times that of water, which was the density of the universe at around the time of the electroweak phase transition. This is well within the regime that is covered by the standard model of cosmology.

Thanks for the upvote. For a Planck unit there, I thought I'd gone mad.

 

[Pizza]

I remember one the latest discussions about t = 0. The singularity should be considered as a mathematical possibility, not necessarily a physically true one, right? What's about the Euclidean space? Flat and infinite. But same thing, why should be matter there everywhere, and why not, and why should this space be born at the big bang? It's just a mathematical frame, the simplest one of any space variations.

 

[PeterDonis]

The singularity should be considered as a mathematical possibility, not necessarily a physically true one, right?

Not quite. It should be considered as an idealized mathematical limit in an idealized model. Even in the context of the idealized model, the limit $t = 0$ does not actually exist physically. And the idealized model does not apply to our actual universe that far back anyway.

why should be matter there everywhere, and why not, and why should this space be born at the big bang?

Because, as far as we can tell, the model that has these things in it matches observations.

 

[Pizza]

One of these observations was that the space is flat. But that's not an argument for what ever, just thinking ...
At my earth-space-time-slice it's 1.30 am now, will have a nap...
Thanks for so much input.

 

[PeterDonis]

One of these observations was that the space is flat

That space is flat, as far as we can tell given the accuracy of our observations, yes. But, as you say, that in itself doesn't tell us much else.

 

[Chronos]

In eternal inflation, and most multiverse scenarios, our universe and all other universes in the multiverse always have and always will be causally disconnected and which means events in these other universes cannot possibly have any consequences in any other universe. Sort of like the refrigerator light fairy.

 

[phinds]

Yes, it was. Fitting the observable universe into the volume of an atom corresponds to a density of around $10^{26}$ times that of water, which was the density of the universe at around the time of the electroweak phase transition. This is well within the regime that is covered by the standard model of cosmology.

Thanks for that correction Peter. I didn't think it was ever that small. I hate being wrong but the one thing I hate more than being wrong is being wrong and thinking I'm right, so I've appreciated this and other corrections you have made to some of my statements.

 

[phinds]

Thanks for the upvote. For a Planck unit there, I thought I'd gone mad.

Only for a Planck time? Should have been longer

Sorry about contributing to the confusion in this thread.

 

[DaveC426913]

It was considerably longer. I am discovering to my dismay, that my knowledge is not expanding at the same rate as modern science. Stuff I learned just a few years ago is being overturned, leaving some of my understanding antiquated.

 

[Smattering]

In eternal inflation, and most multiverse scenarios, our universe and all other universes in the multiverse always have and always will be causally disconnected and which means events in these other universes cannot possibly have any consequences in any other universe. Sort of like the refrigerator light fairy.

Even in a straight forward infinite universe, there are arbitrarily many regions of space that always will be causally disconnected, aren't there?

 

[phinds]

It was considerably longer. I am discovering to my dismay, that my knowledge is not expanding at the same rate as modern science. Stuff I learned just a few years ago is being overturned, leaving some of my understanding antiquated.

Well, you can always do what I do and just make stuff up and let Peter fix it

 

[Chronos]

Even in a straight forward infinite universe, there are arbitrarily many regions of space that always will be causally disconnected, aren't there?

Yes that is true for regions unreachable at light speed given the current age of the universe. But, if they are unreachable at the speed of light over the age of the universe - what could possibly be there to reach?

 

[Smattering]

Yes that is true for regions unreachable at light speed given the current age of the universe. But, if they are unreachable at the speed of light over the age of the universe - what could possibly be there to reach?

I do not get the question. After all, the universe is thought to be homogeneous and isotopic. Thus, I would expect that these regions contain similar structures as ours.

 

[Pizza]

I understood that far enough regions from each other will never interact anymore, due to the expansion, and even worse, to an accelerated one. The horizon is located there, where the expansion becomes faster than the speed of light, depending on the point of view.

 

[phinds]

I understood that far enough regions from each other will never interact anymore, due to the expansion, and even worse, to an accelerated one. The horizon is located there, where the expansion becomes faster than the speed of light, depending on the point of view.

Yes, but smattering's point, and I agree, is that even though there are regions that are not causally connected, they are expected to contain the same distribution of matter as the observable universe.

 

[Pizza]

Unfortunately, that is not part of the standard cosmological model, and Physics Forum is not the place for such speculation.

Because, as far as we can tell, the model that has these things in it matches observations.

It is not my goal to speculate beyond the models or in contradiction to them, rather to understand them better, evaluate the limits, uncertainties etc.

I knew that spacetime was created at the big bang, according to my readings. But I am not sure, if that is just a conclusion or part of the core. I mean, if spacetime is bond to energy or "content" in space, than why could the Euklidean space (its empty part) not have been there since ever and forever? In other words, could the spacetime be born in the Euklidean space, or should the latter be always included in any way?

And even more confusing, nothing was born (somehow), according to the model, because the model starts just after the initial bing bang itself. Consequently I can't see why the Eucl. space shouldn't have existed before that moment, when the model come into play, what ever exactly happened before.

I have not discovered any observations for or against the idea, that far away might happened other big bangs. Let's say with their own spacetime, but when their expansion touchs each other once a day, their spacetimes might be compatible to each other, why not. Same set of constants...
Is it just useless to think about or are there facts excluding this thoughts?

Hope it is still according to the terms of use, otherwise just give me a note please. And yes, will have to read them carefully again.

 

[Pizza]

Yes, but smattering's point, and I agree, is that even though there are regions that are not causally connected, they are expected to contain the same distribution of matter as the observable universe.

I agree too, for what we usually call our universe. Except just if that one has limitations, is finite. How can a big bang lead to an infinite space infinitely filled with matter everywhere? What if 45 billion lightyears or much farer away just the infinite space continues but without any more matter in it?

 

[Smattering]

I agree too, for what we usually call our universe. Except just if that one has limitations, is finite. How can a big bang lead to an infinite space infinitely filled with matter everywhere? What if 45 billion lightyears or much farer away just the infinite space continues but without any more matter in it?

Then, the universe would not be homogeneous and isotropic. As I understand, there is actually no proof that it is homogeneous and isotropic beyond our own Hubble volume, but this is the commonly accepted working hypothesis that most cosmologists are using.