For the first time in the history of science, we at least have a chance of putting together a sensible theory of time and the evolution of the universe.
I'm going to suggest the following way out: The Big Bang was not the beginning of the universe. Cosmologists sometimes say that the Big Bang represents a true boundary to space and time, before which nothing existed— indeed, time itself did not exist, so the concept of "before" isn't strictly applicable. But we don't know enough about the ultimate laws of physics to make a statement like that with confidence. Increasingly, scientists are taking seriously the possibility that the Big Bang is not really a beginning— it's just a phase through which the universe goes, or at least our part of the universe. If that's true, the question of our low- entropy beginnings takes on a different cast: not "Why did the universe start out with such a low entropy?" but rather "Why did our part of the universe pass through a period of such low entropy?"
That might not sound like an easier question, but it's a different one, and it opens up a new set of possible answers. Perhaps the universe we see is only part of a much larger multiverse, which doesn't start in a low- entropy configuration at all. I'll argue that the most sensible model for the multiverse is one in which entropy increases because entropy can always increase— there is no state of maximum entropy. As a bonus, the multiverse can be completely symmetric in time: From some moment in the middle where entropy is high, it evolves in the past and future to states where the entropy is even higher. The universe we see is a tiny sliver of an enormously larger ensemble, and our particular journey from a dense Big Bang to an everlasting emptiness is all part of the wider multiverse's quest to increase its entropy.
via online.wsj.com
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