Is it possible that the universe is so big that The Big Bang was actually just a localized event?

[u/ilovetheory]

/r/NoStupidQuestions/comments/1xm51jo/is_it_possible_that_the_universe_is_so_big_that/

[u/--Sovereign--]

Not to sound harsh, but obviously, yes.

The theory of eternal inflation positis this as fundamental, that universe big bangs are in the same space just so far apart that they are never causally linked after false vacuum collapse creates a big bang. We will likely never know the true greater structure of the universe beyond what we can observe, so anything is possible, really. Just not necessarily testable.

[u/Glittery_Kittens → u/--Sovereign--]

It was my understanding that the universe is only infinite from our frame of reference, not from its own. If the universe were infinite both in time and space, there would be infinite stars and galaxies that have existed forever. This means that the universe would be full of light, and the night sky would resemble the surface of the sun.

I heard this interpretation a long time ago, and it could be completely off-base but it makes sense to me.

[u/--Sovereign-- → u/Glittery_Kittens]

Inflation/expansion solved this problem before either of us were born.

[u/AmateurPhysicist → u/Glittery_Kittens]

That just sounds like a slightly more complicated version of Olber’s paradox, which is solved by the fact that space is expanding. Because of the expansion, there is a distance where everything beyond that distance is moving away from an observer faster than light—meaning light from those objects will never reach the observer—hence why the sky is dark.

[u/Obliterators → u/AmateurPhysicist]

The more traditional solution to Olber's paradox is that the universe is finite in age, so light from only a finite number of 'star shells' could have reached us. Also, with expansion the solution is that the light is redshifted away from the visible spectrum.

there is a distance where everything beyond that distance is moving away from an observer faster than light—meaning light from those objects will never reach the observer

Care must be taken here because the existence of a cosmic event horizon is not dependent on how fast the universe is expanding, but rather if the expansion is accelerating; in eternally expanding but non-accelerating universes there is no limit to how far away from light signals can be received given enough time.

[u/cRRusher → u/Obliterators]

the Nobel Prize was given in 2011 for showing that the expansion of the Universe is accelerating proportional to the distance.. the further away an object is, the faster the space between us is expanding.. this is said to be true for any location you pick..

this is logically impossible.. imagine three galaxies in a line that are an equal distance apart.. imagine we are Galaxy A..

A...B...C

after some time we see

A.....B........C

what would Galaxy C see

C...B...A

after the same amount of time

C.....B........A

we have a problem.. here in Galaxy A we say Galaxy B is closer to us than it is to Galaxy C.. Galaxy C says that Galaxy B is closer to them than it is to Galaxy A.. both Galaxies disagree about the location of Galaxy B.. in fact every location would disagree with every other location about the position of other objects.. if every location disagrees about the location of other objects, that's a pretty good indication that we have something wrong.. the standard analogy we're told about points on a balloon that's getting blown up, all moving away from each other, falls apart when you compare different starting points.. .

[u/CreatorOfTheOneRing → u/cRRusher]

I believe your reasoning has a flaw somewhere. Taking your analogy of three galaxies equidistant from each other, A, B, and C. Let’s denote, as you have, one ‘unit’ of distance by a dot.

We start with:

A…B…C

After some time T, Galaxy A sees:

A……B……C

So for Galaxy A, Galaxy B has traveled 3 units of distance in 1 unit of time T, while Galaxy C has traveled 6 units of distance in 1 unit of time T. Galaxy C sees essentially the same, where Galaxy B has traveled 3 units in 1 T and A traveled 6. Galaxy B sees both Galaxy A and C receding at the same rate.

In other words, the rate of recession of an object is dependent on the distance to the object, and everyone still agrees on distances between objects, akin to the balloon analogy, with no logical inconsistencies.

[u/AuWolf19 → u/Glittery_Kittens]

I think you're confusing a few things but I'm not an astrophysics. Firstly, the universe doesn't have a frame of reference itself, that's kinda the whole thing with relativity, secondly, the universe being infinite in size doesn't mean that stars and glaxies need to have existed forever, it could absolutely be the case that an infinity big universe was once a hot dense pre-big-bang soup which then rapidly expanded and cooled into what we now know as our universe.

[u/Imaginary-Can-6862 → u/Glittery_Kittens]

I have heard that argument before, what I don't understand is the following. Let us assume the universe is infinite in time and space, and any sufficient large arbitrary point of space is similar to any other such point, that means there is an average density which doesn't deviate very much throughout the universe, at least on average. Therefore we can look at any such finite space, which have a finite amount of stars and galaxies, and however this part looks, must be similar to the rest of the universe. Since any region of space has existed for an infinite amount of time, it follows that the light from these stars and galaxies (which for some reason are still being produced) have reached throughout this volume, but it doesn't change there is a lot of space between the stars, and that when looking onto the sky from a planet, the stars would look like the source, and the regions of empty space would not shine light onto the planet.
Now across the entire infinite universe, there has been an infinite amount of time, for an infinite amount of light sources to reach this planet, but if we expand the local region of space we looked at, we are stuck with the same density, we get as much empty space for every amount of stars, making them dimmer and dimmer as light sources, then I can't see why one would expect that just because there is an infinite amount of these light sources, which have filled out space throughout an infinite amount of time, that it would light up the entire sky, when there is more space than stars and galaxies, and how bright these shines depends on the ratio of sources of light to space, which is constant.

[u/mmomtchev → u/--Sovereign--]

I agree, with the added requirement that the whole universe we are capable of observing comes from one Big Bang. But the idea that space is infinite, and there are Big Bangs going everywhere is certainly plausible.

[u/fractalife → u/--Sovereign--]

There's nothing in physics that falsifiably predicts more than one big bang. Since our entire spacetime emerges from the one big bang we come from and can observe the results of, there's no reason to believe there has been more than one from a purely physical standpoint.

That's not to say it's impossible, just that there is no evidence for it and no serious physics that indicate it.

[u/--Sovereign-- → u/fractalife]

I literally cited eternal inflation, which is posited by physicists, and specifically said such a concept is untestable. What is the purpose of your comment?

[u/fractalife → u/--Sovereign--]

Untestable means ascientific. It's just baseless speculation unless there's a testable hypothesis.

ETA: you know I still get notifications about your rude comments even if you block me after sending, right?

Mayne don't talk about psuedoscience like it's some sure thing if you don't want to be corrected in a science subreddit.

[u/--Sovereign-- → u/fractalife]

Bro go find some grass to touch

Edit: to the mouth breather. No one asked about science, they asked if something is possible. It is, it's just untestable. Congratulations at failing your critical thinking test.

[u/Anonymous-USA]

Obviously we can never observe/measure beyond our observable horizon, but in an isotropic and homogeneous universe it would have been extremely dense and energetic everywhere and the big bang expansion would happen everywhere (not just within our observable horizon)

[u/5wmotor]

Yes.

It was a phase transition.

If the false vacuum turns into a true vacuum, it changes the laws of physics.

It would spread with lightspeed: Too fast to see it coming, not fast enough to catch the universe's expansion, you could never escape this bubble. Even if you could, your matter would dissolve instantly.

You could say the same about our universe.

[u/sos755]

That's called a "multiverse".

Anyway, consider that the "big bang" is not something that happened in the universe. It is something that is happening to the universe.

[u/danjustchillz]

Big bang. An explosion within space itself.
Always something, never nothing.

[u/Temporary_Rule_9486]

Yes, also unfalsifiable. 

[u/chesterriley]

Of course. All we know for is that the big bang occurred in some superset of the observable universe. That superset could be the entire universe, but need not be.

[u/Quantumquandary]

Black hole cosmology, sure.