Feb 22, 2011

Talking about Time, Mach and Information

Two weeks ago, I had the pleasure of receiving Julian Barbour here at Aston for a seminar. Julian is a singular physicist and I really admire him. Specially for the path he chose after getting his Ph.D. in the University of Cologne, Germany. Instead of finding an academic position, he decided to finance himself by translating Russian texts part-time. He said to me that he knew he could not fit into the publish or perish academic environment. Well, his first published paper took him many years, but was published in Nature. In addition to that, he's a very nice and very polite person.

When I invited him to Aston, he promptly and kindly agreed to give us a seminar about his work on Mach's Principle. As probably most of you know, Mach's Principle is the idea, first expressed by Ernst Mach, that all movement should be relative. Newtonian physics is based on the assumption that a non-accelerated movement is relative, but whenever acceleration comes into play, there must be a sense in which we can talk about absolute movement. For instance, circular movement should be absolutely accelerated, no matter the referential. Mach, and many philosophers including Poincare, did not like that. They thought, as indeed I think as well, that all movement, accelerated or not, should be relative. The problem is that it doesn't seem that the universe agrees with this point of view.

Well, actually that's what I thought was the content of Mach's Principle before Julian gave his talk. What Julian taught us was that this is only part of it. It seems that the relational point of view has problems that appear even before acceleration comes into play

Another thing that Julian showed was how using Mach's Principle you are able to deduce very interesting physics like gauge theories. You should notice, however, that his work until now is just about classical physics, but Julian also works with quantum gravity and one of his objectives is to attack the problem from that perspective.

The details of all of this can be found in this paper, freely available from the arXiv:
Julian has a book on his ideas about time as well, which I should have read before he came. That would have made our discussions much more fun. Yes... I am buying it now and I am eager to read it. I'll try to post some comments when I finish. Julian idea is the one of the block universe and he also shares David Deutch's enthusiasm with the multiverse idea.

After the seminar we had, as it is usual, a lunch on the Business School and afterwards we spend the rest of the afternoon discussing about his new interest on information theory. He was writing his essay for the Foundational Questions Institute contest whose theme was "Is reality digital or analogue?". His essay is quite interesting and can be read here:

Basically, he argues against the present fashionable position that information is a concept more fundamental than others, for instance, fields. "It from bit" is the famous aphorism created by Wheeler in his phase when he thought that everything should be originated from information. It's a quite enjoyable paper and we here already are planning to discuss it. I would recommend it's reading, as the mathematics is not very difficult. You can also vote for him in the contest. ;)

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