(Photos At Google)
Bryan W. Roberts
Department of History and Philosophy of Science
University of Pittsburgh
September 1, 2008
The Geneva Summer School in Philosophy of Physics, 2008 was a 1-week intensive summer school in the middle of the Swiss alps. This year, from July 27th to August 2nd, 2008, scholars and graduate students met in Arolla's Hotel Mont-Collon for a conference on the nature of space and time. I had the honor to participate, thanks to a generous grant from the Wesley and Merilee Salmon Foundation. What follows is my report on what happened there.
Like much of the philosophy of physics, the Geneva Summer School in Philosophy of Physics this year was inspired by one of those questions that lies near the border of science and the ineffable: What is the nature of space and time? Philosophers make this kind of question more concrete by asking about identity, causation, substance, and dynamical evolution in space and time, as well as about the historical and physical foundations of our best theories.
The strategy of the program was to take some of the top thinkers on these subjects, mix them together with a few dozen graduate students, and stick them all alone in the mountains for a week to work things out. The speakers included Jeremy Butterfield, Dennis Dieks, Nick Huggett, Vincent Lam, Stephan Leuenberger, John Norton, Carlo Rovelli, and Christian Wuthrich. The result was a lively, productive, challenging event, which can hardly be captured by a brief online summary. But I'm going to give it a try.
A typical day consisted of four talks about space and time, each one about an hour long. We came prepared having completed hundreds of pages of reading, so that for half an hour after each talk, there was an interesting and wide-ranging discussion of the presentation. It was very intellectually demanding, but never tiring, as the organizers had the excellent foresight to recharge us with coffee and snacks or a meal after each discussion. The coffee and snacks were on the sunny hotel patio, at the base of three or four dramatic glacial peaks. The meals were in the rustic, lodge-like hotel dining room. For a philosopher of physics, it just doesn't get more glorious than that.
The Geneva Summer School was a fun, interesting, inspiring event that gave dozens of young philosophers of physics a chance to experience what really makes this field great. A blow-by-blow recap simply wouldn't do it justice. So here are a few selected snapshots to give you a little taste.
The Very Middle of Nowhere. Everyone seemed to agree that a lot of the magic of this event was in the location: the Geneva Summer School in Philosophy of Physics is in Arolla, Switzerland which is arguably in the running for the title of the Very Middle of Nowhere. Arolla is dramatically perched at 2000 meters in the Swiss Alps. It contains a convenience store, three small hotels, a souvenir shop and a handful of chalets.
If you would have told me prior to arriving in Arolla that I would be trapped among a hord of philosophers of physics with nowhere to go, I might have been nervous. But the result was delightful: we were all immersed a nearly constant stream of raw, over-the-table philosophical banter -- you might call it philosophy in its purest form. And we all walked away with permanent new friends in the field.
There is a delightful phenomenon that came out of this, which was unusually common at the Geneva Summer School. A handful of philosophers would come together, interact for a while, generating masses of exciting ideas about the philosophy of physics, and then would be flung apart again toward some other adventure: a lecture, a meal, a hike, etc. It was kind of like n- interacting bodies in a chaotic dynamical system.
An example: one evening after dinner, about a dozen philosophers of physics stumbled downstairs to huddle intently around a large oak bar table in the smokey hotel basement. Chris Wuthrich sat on my right clutching a beer, Nick Hugget sat across from him. All three of us were surrounded by summer school participants.
''It cant wobble," said one participant. "The principle of relativity forbids it.''
He was talking about a ball rolling at relativistic speeds without slipping, a question that I had recently begun to dwell on. Such a ball assumes an oblong-ish shape, due to length contraction. But as the participant pointed out, it doesn't wobble, if the Principle of Relativity is going to be preserved. My question was: why? What are the rotational dynamics of such a ball?
Comments and analyses flew around the table, and a solution soon emerged in terms of the asymmetric mass distribution of the relativistic rolling ball. The discussion was fantastic. And within the hour, each of the n-bodies were flung apart again, off to climb some other intellectual peak.
Identity Through Time. The Swiss coffee they served us in the morning was strong. Very strong. So when Christian made the announcement that the morning lecture was beginning, I bounced effortlessly with my to the adjacent conference room. There, Jeremy was preparing a defense of the perdurantist view of identity. Identity is a debate that traditional philosophers have discussed for decades. Jeremy is one of the noble few who is doing this debate an important service, by showing what our best physical theories have to say about these matters.
Jeremy began by discussing how a common argument against perdurantism (called the Rotating Discs Argument -- summarized here) simply breaks down from the perspective of General Relativity. On the other hand, he expressed some sympathy towards the argument that the perdurantist doesn't seem capable of making sense of an object's velocity. But he was able to produce some results, which show that if the perdurantist takes identity to be temporally extended -- that is, based on a length (rather than a moment) of time -- then this argument against perdurantism can be overcome. It was a lovely example of finally bringing some concrete physics to bear on an old philosophical debate.
However, the discussion session afterward illuminated another interesting feature of Jeremy's talk. The debate seemed strange to Carlo Rovelli, who pointed out that one almost never really takes a physical quantity to be a finitely extended "object" -- all of our best physical theories are field theories! This led John Norton to make a very interesting suggestion: might this same debate be carried out for quantities other than objects? How can we describe the identity of a quantity like, say, "energy" through time? These kinds of questions bring philosophy to bear on physics, in order to learn something about fundamental physical quantities. I found myself intrigued that this debate might be a two-way interface between these two areas of study.
Settling a Debate. There are a lot of different ways to do philosophy of physics, and there were many excellent representatives at the Geneva Summer School. We saw philosophical issues tied tightly to historical developments: Dennis Dieks' discussion of Mach's principle and the Einstein Universe; John Norton's illustration of how Einstein discovered his field equations; and Nick Huggett's introduction to the spacetime relationism. There were some technical results, such as Jeremy Butterfield's result that some perdurantists can define velocity, and Dennis Dieks' analysis of how spacetime symmetries are related to simultaneity. Some people focused on highly metaphysical issues, such as Stephan Leuenberger's account of causation, and Vincent Lam's argument for moderate structural realism. And their were more -- all of which had their own virtues.
However, one of the most original approaches to settling a debate came in John Norton's talk. After presenting his deflationary account of causation, John turned to all of us and asked: "Why don't we try something new." Rather than the usual back-and-forth, John suggested that we just put the idea to a vote. He gave us three options: 1) You think this is completely crazy; 2) You think this is so obvious it's almost trivial; or 3) You're not sure what to think. When it came around to the third option, I raised my hand high. John is always very convincing, but I always feel in uncertain territory when it comes to causation. So did everyone else, apparently. So we launched into the usual back-and-forth.
Philosophers On Ice. When most of what you know about someone comes from sitting around a conference table, it's always pleasantly surprising to see what happens when you meet them again outdoors. Arolla, Switzerland is outdoors in a big way. And one afternoon, the organizers rallied the troops for a hike to a nearby glacier. The path was no more than a few kilometers. But it wasn't a walk in the park, either -- huge boulders stood between us and our glacier, and the only way around them was to go right over the top. As it turns out, boulders are no obstacle to philosophers of physics. I was struck as we scrambled from rock to rock at the resilience of my colleagues. As it turns out, they all seemed to have the same strategy that I do, which says that, when there's a mountain in the way, you just lower your head and charge over it. Maybe it's a philosopher of physics thing.
After conquering the glacier, many wandered back to the hotel, but a few decided to look for more mountains to conquer. The latter didn't have to look very far: there was a 4-hour hike straight up standing right in front of us. So half a dozen adventure-seekers (myself included) set out to summit the mountain. When I reached the top, I was rewarded with a view of the alps that could have been the moon, together with a riveting conversation about the gravitational analogue of the Aharanov-Bohm effect. Sheep were baa-ing on the trail below us. It was an unforgettably Swiss experience -- a Swissperience, if you will.
The Geneva Summer School in Philosophy of Physics really began several weeks before the actual event, when we began preparing with huge tomes of assigned reading about the philosophy of space and time. That preparation was crucial to making the event great. The moment I arrived in Arolla, I was suddenly surrounded by dozens of people immersed in the same studies as I was. The lectures helped us to focus our thoughts, and by the end of the week, I think we all had developed a broad and deeply rooted picture of this exciting field.
One of the stated goals of the summer school was to take our education in the philosophy of physics to a new level. When I entered, I thought of myself as a graduate student just beginning to get ahold of a few topics in the philosophy of spacetime. I left feeling like this was something I'd like to do for a living. For that, I would like to express my sincerest thanks and appreciation to the Wesley and Merilee Salmon Foundation, and to the History and Philosophy of Science faculty at the University of Pittsburgh, for giving me this experience.
Department of History and Philosophy of Science
University of Pittsburgh