What existed before our universe existed?

Answer

This is quite a difficult question. Not so much because you would have to be smart and/or be able to calculate hard to answer it. But rather because you have to ask questions about the question itself.

By ‘the universe’ we mean ‘everything that is’, and that includes time and space. If you ask what was before the universe, you assume that there was already time then, and therefore that the universe already existed then!

So when we talk about ‘the origin of the universe’, we also mean that time had a beginning. Why are we doing that? For a number of reasons, but two of them in particular: (1) We see the universe expanding, and if we calculate backward, we find a ‘moment’ about 14 billion years ago when everything must have sat together; (2) We can work out how old the stars and other things in the universe are, even find out which ones are the oldest, and we find an age for the oldest stars that fits well with those fourteen billion years ago. So it seems very much that the universe, and time and space, began 14 billion years ago.

So we can hardly help but conclude that that beginning has been there, and was a real beginning, but that doesn’t mean we fully understand it yet. The ultimate why eludes us, and perhaps always will. Because we must not forget that we are children of this universe, and we learn to speak and think in this universe. If we sense time and space, it is because they are characteristics of the universe that produced us. But that also means that we have to be careful about talking about time and space ‘before’ and ‘beyond’ the universe.

Realizing that we need to be careful doesn’t mean we shouldn’t think further. In the big bang as we try to understand it with classical physics, the world is infinitely small and its density infinitely large, and we cannot say anything about that with the same physics. With more modern theories it may be possible that there are subtle effects at those smallest dimensions, which ‘our’ world has been able to produce from an ‘other’ world. But that is really still a lot of searching.