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Theoretical Physicist, Julian Barbour, Shares his ponderings on time & motion.

You can listen to Julian Barbour's ponderings with the audio file attached or you can read below.

The Universe is not in a box.


I'm asking questions that I've been asking myself now for a very long time. Basically, what is time? What is motion? Even more so, why do we have such a strong sense of moving forward in time, and that things in many ways are getting more and more interesting in the universe?


This has been a puzzle for a long time in science. All the laws of physics suggest there's no distinguished direction of time. The laws of physics work in exactly the same way. For example, if you film two billiard balls colliding and run it backwards, it looks exactly the same. However, you take a film of someone diving into a swimming pool and run that back, it looks completely different. It's been an issue now for about 170 years—why that can be if the laws suggest it should be exactly the same.


About seven years ago, I got an idea that might solve that problem, which came out of more fundamental questions I'd been asking. Just how do you define distance? How do you define motion? We always see things relative to other objects in the universe. Newton had introduced this concept called absolute space. It's a little bit like a room with the walls taken away. In this room where I'm sitting with you now, my position relative to the chair and the walls is perfectly clear. You can see that. Newton somehow imagined that we move in a space, which is as if the room was there but the walls have somehow disappeared. This has been a mystery in physics for a very long time, and it was the stimulus that led Einstein to create his general theory of relativity, which, in the end, finished up in rather a muddled state because Einstein didn't try and do it directly; he worked indirectly.