Sunday, July 28, 2013

Think About Nature


The main question I'm asking myself, the question that puts everything together, is how to do cosmology; how to make a theory of the universe as a whole system. This is said to be the golden age of cosmology and it is from an observational point of view, but from a theoretical point of view it's almost a disaster. It's crazy the kind of ideas that we find ourselves thinking about. And I find myself wanting to go back to basics—to basic ideas and basic principles—and understand how we describe the world in a physical theory.

What's the role of mathematics? Why does mathematics come into physics? What's the nature of time? These two things are very related since mathematical description is supposed to be outside of time. And I've come to a long evolution since the late 80's to a position, which is quite different from the ones that I had originally, and quite surprising even to me. But let me get to it bit by bit. Let me build up the questions and the problems that arise.

One way to start is what I call "physics in a box" or, theories of small isolated systems. The way we've learned to do this is to make an accounting or an itinerary—a listing of the possible states of a system. How can a possible system be? What are the possible configurations? What were the possible states? If it's a glass of Coca Cola, what are the possible positions and states of all the atoms in the glass? Once we know that, we ask, how do the states change? And the metaphor here—which comes from atomism that comes from Democritus and Lucretius—is that physics is nothing but atoms moving in a void and the atoms never change. The atoms have properties like mass and charge that never change in time. The void—which is space in the old days never changed in time—was fixed and they moved according to laws, which were originally given by or tried to be given by Descartes and Galileo, given by Newton much more successfully.

And up until the modern era, where we describe them in quantum mechanics, the laws also never changed. The laws lets us predict where the positions of the atoms will be at a later time, if we know the positions of all the atoms at a given moment. That's how we do physics and I call that the Newtonian Paradigm because it was invented by Newton. And behind the Newtonian Paradigm is the idea that the laws of nature are timeless; they act on the system, so to speak, from outside the system and they evolve from the past to the present to the future. If you know the state any time, you can predict the state at any other time. So this is the framework for doing physics and it's been very successful. And I'm not challenging its success within the proper domain—small parts of the universe.

The problem that I've identified—that I think is at the root of a lot of the spinning of our wheels and confusion of contemporary physics and cosmology—is that you can't just take this method of doing science and scale it up to the universe as a whole. When you do, you run into questions that you can't answer. You end up with fallacies; you end up saying silly things. One reason is that, on a cosmological scale, the questions that we want to understand are not just what are the laws, but why are these the laws rather than other laws? Where do the laws come from? What makes the laws what they are? And if the laws are input to the method, the method will never explain the laws because they're input.

Also, given the state of the universe of the system at one time, we use the laws to predict the state at a later time. But what was the cause of the state that we started with that initial time? Well, it was something in the past so we have to evolve from further into the past. And what was the reason for that past state? Well, that was something further and further in the past. So we end up at the Big Bang. It ends up that any explanation for why are we sitting in this room—why is the earth in orbit around the sun where it is now—any question of detail that we want to ask about the universe ends up being pushed back using the laws to the initial conditions of the Big Bang.

And then we end up with wondering, why were those initial conditions chosen? Why that particular set of initial conditions? Now we're using a different language. We're not talking about particles and Newton's laws, we're talking about quantum field theory. But the question is the same; what chose the initial conditions? And since the initial conditions are input to this method that Newton developed, it can't be explained within that method. So if we want to ask cosmological questions, if we want to really explain everything, we need to apply a different method. We need to have a different starting point.

by Lee Smolan, Edge |  Read more:
Image: uncredited