BARBOUR: As it happens, this is about an issue very closely related to quantum cosmology. What is the meaning of general covariance? Empson is arguing that it is a tautology. I think he is right in that but not in the claim that all law becomes the assumption of the description. Tensors relate different things and bring them into lawful connection.
Let's consider a great experience I just had. I witnessed the total eclipse of the sun in France on August 11th. I remember vividly reading as a boy that there would be this eclipse in 1999, the first one visible in England in a long time actually I went over to France to see it. Now there isn't any doubt about an eclipse; either you see an eclipse or you don't. The astronomers predicted that it would be seen as total in the medieval town of Senlis just north of Paris, and sure enough we did see it total. That's pretty impressive. I don't think there's anything to do with inventing there the impression of actually seeing the sun totally eclipsed is quite unambiguous. My memories of reading about the eclipse as a boy and my memory of the actual eclipse are not tensors but they are real different things that match up. That's why I believe there's something real out there in the world and that we are getting our hands on it.
JB: Your theories appear to be bumping up against the ideas of many of your colleagues? Who might be sympathetic?
BARBOUR: The string theorists will probably not take it very seriously, because I'm tied to a certain approach to attacking the problem and they will perhaps just say well he's doing the wrong thing. But I don't worry too much about that, because certain approaches can become unpopular for a long time and then come back in again. There are certainly people who do think about the fundamental issues of how you describe the world and these very basic questions of what is motion and so forth; they should be sympathetic to my approach. The people who will not like me are the people who don't want to take the many worlds interpretation of quantum mechanics seriously, and who are trying to modify quantum mechanics so as to banish that specter. I don't think Roger Penrose would take it very seriously, because he doesn't like any form of the many worlds interpretation of quantum mechanics. Stephen Hawking might be quite sympathetic, because he's been basically working along those lines for many years now. Other people who I would not expect to be sympathetic are Murray Gell Mann, Jim Hartle, and several others who have developed the so called consistent histories approach to the interpretation of quantum mechanics. They start out by taking a complete history as being a fundamental concept, whereas for me the Now is the starting point. They start with a string of Nows.
JB: Lee Smolin certainly talks about your ideas.
BARBOUR: Lee and I are great friends, and we've talked a lot and we've developed ideas together we don't follow exactly the same line now, but we share a lot in common. We are both very interested in structure, and in thinking that the way things are structured is the really important thing. That relates to this basic issue of whether the world exists in some all powerful background or whether the world is really just an interaction between the things that are in it. We share that view very much.