100 XR Radio And find out if he agrees with Paul Dirac about beauty and the truth of science. Thanks very much for allowing me into your department, Stephen. Can I ask you straight away, is beauty important for you in your scientific work? I don't know about beauty, but the fundamental laws of the universe should be elegant. What do you mean by elegant? An equation is elegant if it is short, simple and explains properties of the universe that were previously not accounted for. My most elegant equation is very simple. It is S = a quarter A. Here, A is the area of the boundary of a black hole. And S is its entropy, a measure of how much heat it contains. What does that mean? This equation shows that black holes aren't completely black. They glow like hot bodies and lose energy and mass. Eventually they will disappear in a tremendous explosion. Why is that an elegant equation? The equation came from a rather messy calculation. It seemed a miracle that such a concise equation should result. This equation unravels the physics of black holes, one of the most mysterious objects in the universe. As I understand it, the equation says that as stuff falls into the black hole, the surface area of the black hole gets bigger, and the entropy does too. In , when Stephen Hawking came up with his equation, there was still some doubt as to whether black holes existed.years on, all scientists agree they do. Black holes have entered the realm of science fact. While making this film, I found out that Paul Dirac believed that it was more important to have beauty in one's equation than to have the equation backed up by actual experiment. Is this too extreme a view for you? I think what Dirac meant was that although a beautiful equation might not agree with experiment at a particular time, it will eventually turn out to be true in the long run. I think elegance is a good guide for Radio but not an infallible one. In art, an artist like Picasso say, will just be working from hour to hour, from work to work, pushing his ideas along with his work. He doesn't necessarily think, "Now, I've discovered cubism." That accolade will be bestowed upon his work a bit later by other people. But he probably will, at some point, think, "I have made some kind of breakthrough here." 100 XR Radio And I wonder if that breakthrough feeling, if there's an equivalent for you in your type of enquiry. There's nothing like the Eureka moment of discovering something that noone knew before. I won't compare it to sex, but it lasts longer. Thank you very much, Stephen. Thank you. The very fact that Stephen agreed to be interviewed by me, when it's not an easy task for him, it's not something that he does a lot, proves to me that he believes in the thesis that beauty is a significant element in the work of a theoretical scientist. That making an equation calls for some kind of, not just a sense of beauty, but almost a pursuit of it. The pursuit of beauty really is a sort of driving force in evolving an equation. I've got to let all that sink in now. I've been very happy to have my head crammed full of unfamiliar ideas, 100 XR Radio but now there's one more thing I need to do.