What existed before the big bang? What is the nature of time? Is our universe one of many? On the big questions science cannot (yet?) answer, a new crop of philosophers are trying to provide answers.
Last May, Stephen Hawking gave a talk at Google's Zeitgeist Conference in which he declared philosophy to be dead. In his book The Grand Design, Hawking went even further. "How can we understand the world in which we find ourselves? How does the universe behave? What is the nature of reality? Where did all this come from? Traditionally these were questions for philosophy, but philosophy is dead," Hawking wrote. "Philosophy has not kept up with modern developments in science, particularly physics."
In December, a group of professors from America's top philosophy departments, including Rutgers,* Columbia, Yale, and NYU, set out to establish the philosophy of cosmology as a new field of study within the philosophy of physics. The group aims to bring a philosophical approach to the basic questions at the heart of physics, including those concerning the nature, age and fate of the universe. This past week, a second group of scholars from Oxford and Cambridge announced their intention to launch a similar project in the United Kingdom.
One of the founding members of the American group, Tim Maudlin, was recently hired by New York University, the top ranked philosophy department in the English-speaking world. Maudlin is a philosopher of physics whose interests range from the foundations of physics, to topics more firmly within the domain of philosophy, like metaphysics and logic.
Yesterday I spoke with Maudlin by phone about cosmology, multiple universes, the nature of time, the odds of extraterrestrial life, and why Stephen Hawking is wrong about philosophy.
Your group has identified the central goal of the philosophy of cosmology to be the pursuit of outstanding conceptual problems at the foundations of cosmology. As you see it, what are the most striking of those problems?
Maudlin: So, I guess I would divide that into two classes. There are foundational problems and interpretational problems in physics, generally --say, in quantum theory, or in space-time theory, or in trying to come up with a quantum theory of gravity-- that people will worry about even if they're not doing what you would call the philosophy of cosmology. But sometimes those problems manifest themselves in striking ways when you look at them on a cosmological scale. So some of this is just a different window on what we would think of as foundational problems in physics, generally.
Then there are problems that are fairly specific to cosmology. Standard cosmology, or what was considered standard cosmology twenty years ago, led people to the conclude that the universe that we see around us began in a big bang, or put another way, in some very hot, very dense state. And if you think about the characteristics of that state, in order to explain the evolution of the universe, that state had to be a very low entropy state, and there's a line of thought that says that anything that is very low entropy is in some sense very improbable or unlikely. And if you carry that line of thought forward, you then say "Well gee, you're telling me the universe began in some extremely unlikely or improbable state" and you wonder is there any explanation for that. Is there any principle that you can use to account for the big bang state?
This question of accounting for what we call the "big bang state" is probably the most important question within the philosophy of cosmology.
This question of accounting for what we call the "big bang state" -- the search for a physical explanation of it -- is probably the most important question within the philosophy of cosmology, and there are a couple different lines of thought about it. One that's becoming more and more prevalent in the physics community is the idea that the big bang state itself arose out of some previous condition, and that therefore there might be an explanation of it in terms of the previously existing dynamics by which it came about. There are other ideas, for instance that maybe there might be special sorts of laws, or special sorts of explanatory principles, that would apply uniquely to the initial state of the universe.
One common strategy for thinking about this is to suggest that what we used to call the whole universe is just a small part of everything there is, and
that we live in a kind of bubble universe, a small region of something much larger. And the beginning of this region, what we call the big bang, came
about by some physical process, from something before it, and that we happen to find ourselves in this region because this is a region that can support
life. The idea being that there are lots of these bubble universes, maybe an infinite number of bubble universes, all very different from one another. Part of the explanation of what's called the anthropic principle says, "Well now, if that's the case, we as living beings will certainly find
ourselves in one of those bubbles that happens to support living beings." That gives you a kind of account for why the universe we see around us has
Is the philosophy of cosmology as a project, a kind of translating then, of existing physics into a more common language of meaning, or into discrete, recognizable concepts? Or do you expect that it will contribute directly to physics, whether that means suggesting new experiments or participating directly in theoretical physics?
Maudlin: I don't think this is a translation project. This is a branch of the philosophy of physics, in which you happen to be treating the entire universe --which is one huge physical object-- as a subject of study, rather than say studying just electrons by themselves, or studying only the solar system. There are particular physical problems, problems of explanation, which arise in thinking about the entire universe, which don't arise when you consider only its smaller systems. I see this as trying to articulate what those particular problems are, and what the avenues are for solving them, rather than trying to translate from physics into some other language. This is all within the purview of a scientific attempt to come to grips with the physical world.
There's a story about scientific discovery that we all learn in school, the story of Isaac Newton discovering gravity after being struck by an apple. That story is now thought by some to have been a myth, but suppose that it were true, or that it was a substitute for some similar, or analogous, eureka moment. Do you consider a breakthrough like that, which isn't contingent on any new or specialized observations to be philosophical in nature?
Maudlin: What occurred to Newton was that there was a force of gravity, which of course everybody knew about, it's not like he actually discovered gravity-- everybody knew there was such a thing as gravity. But if you go back into antiquity, the way that the celestial objects, the moon, the sun, and the planets, were treated by astronomy had nothing to do with the way things on earth were treated. These were entirely different realms, and what Newton realized was that there had to be a force holding the moon in orbit around the earth. This is not something that Aristotle or his predecessors thought, because they were treating the planets and the moon as though they just naturally went around in circles. Newton realized there had to be some force holding the moon in its orbit around the earth, to keep it from wandering off, and he knew also there was a force that was pulling the apple down to the earth. And so what suddenly struck him was that those could be one and the same thing, the same force.