[GW150914]

It’s similar only if you misunderstand the questions physics seeks to answer. “If we rewind time according to present observations and theories, what do we see?” The answer is a Big Bang event, but that is just the answer to the question posed, not the deeper one posed by the wiki article. If you ask “why is there something rather than nothing?” physics has no single clear answer. Science takes very limited questions and seeks to answer them in a limited fashion with a high degree of confidence. Metaphysics plays word games with philosophy because hey, who can really gainsay you? Maybe it’s D-Branes, maybe it’s eternal inflation, maybe it’s the Great Green Arkleseizure.

The problem is that popular science and people who don’t know better misunderstand the nature of what physics actually does and tries to shoehorn theories into the questions they want answered.

[d0lph]

I think the question in that case is what existed before the Big Bang, has a vacuum always existed before? Or are we on a constant loop of universes forming and disintegrating.

[lifeformed]

I think the answer is that the concept of "before the Big Bang" doesn't make sense. Time is a part of the universe, and so there is no "missing" time or space before it. I think Steven Hawking said that it's like asking what is north of the north pole.

[beaconstudios]

I think the heart of the issue is that the big bang is confusing to our understanding of causality. What caused the matter to exist in the original singularity? Before it was a singularity, was it some other form or had it always existed as such? What triggered the big bang?

Based on the first law of thermodynamics we can figure that a constant quantity of energy (in the form of both energy and mass) has always existed, but then the question remains - why does it exist?

[d0lph]

How could time not exist?

[GW150914]

That’s a question which may or may not be meaningful in the first place. In the classic formulation it’s a meaningless question, because time and space expanded from a singularity in the BB event, so there is no “before” just as there is nothing into which space expanded. The vacuum exists within the context of spacetime and the universe after all.

Maybe it was part of a cyclical series of events as you suggests, Big Bang followed by Crunch, and then Bang again. Maybe the String Theorists are eight and it’s cyclic and ekpyrotic, and our universe is just a burst of energy release by interacting Branes. Maybe none of that is right and some other model which better fits observations and predictions will turn out to be better.

One thing to keep in mind is just how tricky it can be to ask seemingly good and simple questions about these things. People come into this with a lot of assumptions and intuition that tends to fail at thes scales. Classic questions that don’t actually mean anything in the formalism are, “What is space expanding into? What came before the Big Bang?” There are other models which accommodate these questions such as eternal inflation in the context of a multiverse, but not in the formalism.

[state_less]

Might not be looping through the same events but rather through every variation. Which could explain how we finally get here. It feels like we are way out in the countryside of what's possible in the universe.

And it's hard to say where we are and what time it is.