This was kind of a hasty type up, I probably made some mistakes bum-rushing this but whatever.
Do I believe in the Big Bang:
The Big Bang is currently the prevailing cosmological model supported by substantial evidence.
The Big Bang is an extremely dense state of high energy and it's an event on the smallest possible scale at the highest possible energy.
The part on the Big Bang fits with the few details that we do know about that era, so it might be right on the parts that we don't know.
Really you're extrapolating backwards through General Relativity and reaching a point of infinite density but GR begins to break down at this point. Other theories attempt to explain this like quantum gravity.
en.wikipedia.org
Assuming that the Big Bang occurred at the start of this universe, what existed before it was the potential for the existence of this universe.
The cyclic universe seems very reasonable, but I have no evidence. I don't know of any good evidence for a perpetual universe, but I still keep my mind open to it.
en.wikipedia.org
en.wikipedia.org
What was before: Presumably a vast sea of pure unstable energy drifting through an undefined spacetime grid.
Mass coalesced from energy to form bosons, mesons, gluons, etc., spacetime expanded.
en.wikipedia.org
The hypothetical conditions at the and of the universe, given current models, will match those at the beginning. This model has its flaws.
en.wikipedia.org
en.wikipedia.org
The Theory of Inflation is the most common for describing what happened at the beginning. It proposes an extremely rapid expansion of space moments after the Big Bang. The whole idea is as the universe cools you get broken symmetries.If you regress you get to a state of restored-symmetry. At this point, electroweak symmetry had not yet broken. So prior to expansion, the Higgs Field (the Higgs boson is a manifestation of this) wouldn't work under such extreme circumstances.
Particles without mass travel can at the maximum speed of the universe (light speed), so they have no "clocks," ala they experience no time. This makes an aeon and a second feel the same. Look into photons, they are massless. From their perspective, the moment the sun emitted it, the same moment it was absorbed. From our perspective, it took ~8 minutes. Without mass you don't have tools to measure the size of the universe.
en.wikipedia.org
en.wikipedia.org
I am pretty sure it is expanding. I'm less convinced that it underwent superluminal inflation when it was very young (there is a fair amount of evidence that it did, but not conclusive evidence). Distant parts probably are, but we can't see them when they are or after they do.
In contrast, "inflated" parts are currently visible.
You can call areas outside of the observable universe (our bubble) a parallel universe since it would never be reachable, or so we now think (current space-time laws). This is one version of the multiverse. If the universe is infinite then you have these areas that you're never going to reach so thats why in this sense a multiverse.
The speed of light is through space-time so we don't know if there's stuff beyond space-time. But in theoretical physics there is. The brane and the bulk so there's other actual potential physical dimensions. Things that connect blackholes, whats outside of things connecting them.
That is often seen as the lowest level of the multiverse and parallel universes.
I suspect that the multiverse includes universes with different laws as well as extensions of our universe.
The hypothesis I have considered the most recently is: Everything that can exist always exists, and the set of all things that can exist should properly be called the Omniverse. However we do not know whether what can exist forms a continuum, in which case the multiverse is the same as the Omniverse, or whether existences cluster, in which case our local cluster is the multi-verse and the set of all clusters is the Omniverse (and there may be levels of hierarchy in between).
The consensus for more than 40 years is that inflation happened before the Big Bang. There was this rapid expansion of space-time but the Big Bangis more actually like the dumping of energy into this place. Plank-order seconds after the Big Bang all of this was happening. The Big Bang doesn't have much to do with the expansion of the universe. It has a lot more to do with the dumping pf energy. Mass and energy are fundamentally related and they come from quantum fields. The expansion was already happening and we know the universe is expanding due to dark energy. The Big Bang is just the moment of creation in the sense of the stuff in this place that we know of. Before the Big Bang we know there was only inflation. We can only say from what we currently understand, what happened at the end stages of inflation. Before those final stages of inflation we don't know what happened. Some people think the universe might have started in a
singularity. Before those final stages of inflation the universe was very small so people just jump to the logical conclusion of maybe it started in a singularity. Presumably quantum fields also existed before the Big Bang, so we don't know where they came from. It makes sense to say that outside of space-time itself there may not be time because time is part of this thing and its interwoven with space in some weird way. But that would be looking at General Relativity and taking what it says very seriously so it all gets very tricky.
en.wikipedia.org
We don't know what time is. If you look at time in the sense of General Relativity which is a great theory with a lot of evidence for it but then there's Quantum Theory which there's also a lot of evidence for and paints a very different picture of time. So they're the two ideas of time but we know they're both incompatible so what is time.
The part on time is often considered the greatest incompatibility between general relativity and quantum dynamics.
en.wikipedia.org
Some of those stars are so far away, that it takes their light millions of years to reach earth, and the stars themselves have already burned out so you're looking into the past.
Maybe it really is impossible to move through the observable universe given how big it is. We know for a fact that the universe is constantly expanding and we're going further and further past a certain threshold where we will never able to reach certain parts of the universe even with being able to travel at light speed. We know this is true if the universe keeps expanding the way it seems to be expanding now, but we do not know how the expansion will change in the future. We do not know if the local universe is truly infinite.
Inflation is one of the not-to-unreasonable possible answers to why the universe is as smooth as it is on large scales.
I do not believe it or disbelieve it, having insufficient evidence to reach a conclusion.
Space itself expanding explains the increasing redshift with distance, but I agree that it is not the only way to look at it.
I know of no evidence that the universe is contracting at large scales.
In contrast, there is considerable evidence that the universe is expanding at large scales, and some evidence that the expansion is accelerating (although another possibility is that type I supernovas were different at different times due to the different chemistries of the stars from which they formed).
But, as Einstein said, it is an extraordinarily persistent illusion
As far as I know, the universe is not expanding into anything , it is expanding into nothing.
