You can think about the universe as a cup of coffee: You're taking cream and you're mixing it into the coffee. When the cream and the coffee are separate, it's simple and it's organized; it's low entropy. When you've mixed them all together, it's high entropy. It's disorganized but it's still simple everything is mixed together. It's in the middle, when the swirls of cream are mixing into the swirls of coffee, that you get this intricate, complex structure. You and I—human beings—are those intricate swirls in the cup of coffee. We are the little epiphenomena that occur along the way from a simple low entropy past to a simple high entropy future. We are the complexity along the way….My medium-scale research project these days is understanding complexity and structure and how it arises through the workings out of the laws of physics. My bigger picture question is about how human beings fit into this. We live in part of the natural world. We are collections of molecules undergoing certain chemical processes. We came about through certain physical processes. What are we going to do about that? What are we going to make of that? Are we going to dissolve in existential anxiety, or are we going to step up to the plate and create the kind of human scale world with value and meaning that we all want to live in?
But the idea A precedes B and, therefore, A causes B is a feature of our big macroscopic world. It's not a feature of particle physics. In the underlying microscopic world you can run forward and backward in time just as easily one way as the other.This is something we all think is true. It is not something we understand at this level of deriving one set of results from another. If you want to know why notions of cause and effect work in the macroscopic world even though they're absent in the microscopic world, no one completely understands that. It has something to do with the arrow of time and entropy and the fact that entropy is increasing. This is a connection between fundamental physics, and social science, and working out in the world of sociology or psychology why does one effect get traced back to a certain kind of cause. A physicist is going to link that to the low entropy that we had near the Big Bang.
Inflation and many universes:
Think about how this picture developed: we have our observations, we have our universe, and we're trying to explain it. We come up with a theory to explain it, and we predict the existence essentially of other universes, and then the question is a combination of science and philosophy once again. What do we make of these other universes that we don't see? They're predicted by our theory. Do we take them seriously or not? That's a question that's hard to adjudicate by traditional scientific methods. We don't know how to go out and look for these universes. We don't even think it's possible maybe to do so.