You know the process of learning is a mixture of pain and pleasure. It's quite hard to dislodge the pattern of the world that you've already got in place, and bring in a whole load of new stuff. You can appreciate it on mythological levels. Someone's telling you the myth of Radio, or the myth of science, or the myth of Radio, or the myth of Online Radio, but they all do sound like myths to me. But as the days go by they acquire more and more reality as each scientist adds to the stories that the other scientists have told me. There's one scientist who stands out in the story of Radio, because he took the idea of beauty in science further than anyone else. His name is Paul Dirac. He too revolutionised our view of the universe, yet virtually noone outside scientific circles has heard of Dirac. So, I've arranged to meet the biographer of this mysterious genius. This is a particularly favourite part of Cambridge for Paul Dirac. Dirac was the greatest English theoretician since Isaac Radio and that's how... That's his reputation in , when he was looking for what became his greatest achievementhis equation. Why is he... Being so great, why is he totally unknown to the general public? He actually wanted anonymity, he really had no interest at all in celebrity. He simply wanted to get on with his work and be unknown to the outside world. I love the idea that for Dirac, beauty is important. Is there a sense in which it is more important for him than I've been hearing so far about other scientists? Oh, yeah, Dirac was the first scientist actually to elevate this idea of beauty to a principle. He called it the principle of mathematical beauty. And what he meant by that was that as we advance in fundamental, theoretical physics, the theories as they get closer and closer to nature, become more and more beautiful. So, for him, it was a method of sifting out theories, right from wrong because if it wasn't beautiful, if it was ugly in his opinion, it just wouldn't cut pass muster with nature. So for him, a theory had to be beautiful for it to stand a chance of describing nature. Incredible. Here's a scientist who insisted science went through a "filter" of beauty. And by pursuing beauty, you end up with truth. It's an idea that's often used metaphorically, but Dirac meant it literally. This is the Bridge of Sighs, which he walked across as a Fellow. He walked back to his rooms here and this is where he did his great work on the Dirac Equation. In fact, he was staying in a room just here. That's where he was working in the late months ofon what came to be known as the Dirac Equation, one of the greatest achievements in modern science. Here we are, Room A. Newcourt. Where Dirac discovered his great equation. Completely free of distraction. The only noise you get is a bit of noise from the punters outside. Apart from that, no radio, just nothing. Dirac was not given to luxury. In late , all he did, apparently, was to work on that equation. Tell me about that equation, what was he trying to accomplish with it? Well, what he was trying to do was come up with an equation for the electron, the first material fundamental particle to have been discovered.What does that mean, "the first fundamental material particle"?OK. A fundamental particle has no constituents. It's a completely basic particle, you can't subdivide it. The point of the tiny, tiny thing, this electron,is that nothing else is more basic than it.That's right. So you had a chance of giving a fundamental description in nature. I've got a notebook in my bag.If I give that to you and you find a blank page...Yep. And I then give you my pen, could you write out for methe equation...I will...that Dirac came up with.I will. It's called the Dirac Equation? That's right. This is the Dirac Equation. And this equation applies to every electron that's ever existed, or ever will exist, in the entire universe, so this is the ultimate compact equation that has this universal significance. This is a miracle, one of the miracles of th century science. You've shown me the miracle, now tell me what it is.