# Multiple big bangs in one continuum - Question

1. Nov 12, 2015

### 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.

2. Nov 12, 2015

### 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.

3. Nov 12, 2015

### 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.

4. Nov 12, 2015

### DaveC426913

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.

5. Nov 12, 2015

### 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.

6. Nov 12, 2015

### Staff: Mentor

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".

7. Nov 12, 2015

### Staff: Mentor

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

8. Nov 12, 2015

### Smattering

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?

9. Nov 12, 2015

### phinds

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.

10. Nov 12, 2015

### Staff: Mentor

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.

11. Nov 12, 2015

### Pizza

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.

12. Nov 12, 2015

### Staff: Mentor

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.

13. Nov 12, 2015

### DaveC426913

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

14. Nov 12, 2015

### 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.

15. Nov 12, 2015

### Staff: Mentor

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.

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

16. Nov 12, 2015

### 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.

17. Nov 12, 2015

### Staff: Mentor

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.

18. Nov 12, 2015

### 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.

19. Nov 12, 2015

### phinds

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.

20. Nov 12, 2015

### phinds

Only for a Planck time? Should have been longer