[Sally Le Page (OP)]

Dave asked us:

"It is almost universally accepted that the Universe was the result of THE Big bang. Note the capitalization. Is it possible that the Big Bang is not the only such event that has occurred since the initial one i.e. is it possible there has been more than one, in two or more places separated in time and place? Not dimensionally, as this would clearly complicate matters.
What would the theoretical effects be if whilst one universe existed a second universe was created alongside by another such event. Obviously if the Big Bang could occur spontaneously once, what precludes an event of a similar nature occurring again and why could this event not occur or occur again at numerous times and places."

Any ideas?

[Halc]

It is almost universally accepted that the Universe was the result of THE Big bang.

In context of discussion of other bangs, it is referred to as just 'a big bang'. There's only one of direct importance to us, so reference as THE big bang is appropriate. We know which one is being talked about.

Note the capitalization. Is it possible that the Big Bang is not the only such event that has occurred since the initial one

Calling ours the 'initial one' assumes all kinds of things, like they're ordered, and that ours is special. Again in such contexts (such as eternal inflation theory), we're just one bubble among countless others, each with its own physics. This is a common framework that answers the so-called fine-tuning problem. The other bubbles all have different tunings and only those with optimal tunings evolve observers.

i.e. is it possible there has been more than one, in two or more places separated in time and place?

THE big bang did not take place in a time or place. It defines our time and space, but there's not a location where it happened, and it defines our time-zero, as does any bang with a single time dimension. No,by no viable theory can a bang occur in existing time and space as we know it.

[geordief]

Again in such contexts (such as eternal inflation theory), we're just one bubble among countless others, each with its own physics

In that theory are there any  points common to any two (or more) of the bubbles?

[Eternal Student]

Hi.

Looking at the OP,  that is just too big a question to answer in 2 minutes.   How long are you going to have in your podcast?

1. Halc has already made some good points.
2. There are cosmological models that involve repeating cycles of a big bang followed by big crunch.
3.  String theorists consider the possibility of collisions between branes behaving as (or causing) big bang events.
4.  Black holes offer the possibility of big bang or big crunch events being contained within our spacetime.

[Halc]

Again in such contexts (such as eternal inflation theory), we're just one bubble among countless others, each with its own physics

In that theory are there any  points common to any two (or more) of the bubbles?

There are not 'points' defined in any geometric sense. There isn't some fixed quantity of spatial dimensions or anything that might correspond to an ordering of events or bubbles. None of the geometric rules that we find intuitive really apply.

That said, I think the theory posits an edge to our universe, and a 'beyond' which has a meaning of sorts, if not 3D space as we know it.

There are cosmological models that involve repeating cycles of a big bang followed by big crunch.

Those models don't involve the bang or the crunch happening at a location in space and not elsewhere.

[geordief]

There are not 'points' defined in any geometric sense. There isn't some fixed quantity of spatial dimensions or anything that might correspond to an ordering of events or bubbles. None of the geometric rules that we find intuitive really apply.

That said, I think the theory posits an edge to our universe, and a 'beyond' which has a meaning of sorts, if not 3D space as we know it

Well ,does the theory posit that the bubbles could share an interaction at any "point"?

Do interactions (in "basic" GR)actually define what  any "point" is? Do we have interactions/events rather than points?Are interactions frame-independent by definition and points in spacetime frame-dependent by definition?

[Eternal Student]

Hi Halc.

Quote from: Eternal Student on Today at 00:57:18

    There are cosmological models that involve repeating cycles of a big bang followed by big crunch.

Those models don't involve the bang or the crunch happening at a location in space and not elsewhere.

That is correct.  I suppose they can be eliminated from the discussion since the OP has asked for the bangs to be separated by time and space and they do seem to be using our ordinary time and space in that requirement. 
    However, after a "bounce" or big crunch / big bang event, we are not required to assume that the newly formed spacetime is the same or uses the same dimensions as what might be described as the former spacetime.  So the space, or the place where a bang occurred could be considered as being a different place.  It's a bit metaphysical and the OP does seem to have tried to rule out situations where we consider separation of places or times like this:

(in describing bangs as separated in place and time they state)...Not dimensionally, as this would clearly complicate matters.

    Drop out all mention of cosmological models where a "bounce" occurs if you like.

     I still think one of the problems we would run into is the OP's demand that we do not consider bangs that are separated dimensionally.   A bang will tend to create a new spacetime and that will usually have dimensions of its own - we can't ask it not to do this.

What would the theoretical effects be if whilst one universe existed a second universe was created alongside by another such event.

     You may have to answer that by suggesting that it is very hard to imagine a second universe "alongside" our own universe.   The other universe does not have to share our dimensions.  There may not be any sense in which we can say it is "alongside" without considering a higher-dimensional space in which both our universe and the other universe can be both be said to exist.   A second universe may be self-contained and non-interacting with our own, although it may interact somehow.

[Eternal Student]

Hi geordief,

You asked...

In that theory are there any  points common to any two (or more) of the bubbles?

    I'm not an expert in the eternal inflation model.   However the notion of a "bubble" isn't that it has to be round or bubble shaped.  The early theories tried very hard to find ways in which bubbles could coalesce.  If two bubbles had a point in common then they wouldn't be considered as two bubbles, they would be one big common bubble.  (To the best of my knowledge).

[geordief]

Hi geordief,

You asked...

In that theory are there any  points common to any two (or more) of the bubbles?

    I'm not an expert in the eternal inflation model.   However the notion of a "bubble" isn't that it has to be round or bubble shaped.  The early theories tried very hard to find ways in which bubbles could coalesce.  If two bubbles had a point in common then they wouldn't be considered as two bubbles, they would be one big common bubble.  (To the best of my knowledge).

And that "bi/poly-bubble" would then have to  everywhere follow the same laws of physics as pertain where we are? (according to theory)

If the bubbles were entirely separate  from one another might they still be connected by the processes involved in  "bubble creation"?

A weird question  I grant.(if it makes any sense to ask it)

[Eternal Student]

Hi geordief,

I'm not an expert in eternal inflation.  I've said that before but it's worth stating it again.
I can't give you reliable answers.  Sorry.

[yor_on]

Halc put it very nicely. We don't know wherefrom it came, but it created what we have. To know if there was more of this is impossible, but assuming it was nothing special it's possible. This is presuming a Big Bang, inflation etc to be correct.
=

You will need a different set of physics though to define it, before our origin. It's one of those singularities we can't penetrate.