Two months ago, the Institute of Physics revealed this YouTube video:
Edward Witten, whom they still call "a 2010 Newton Medal Winner" rather than the "An Inaugural Milner Prize Winner" because they think that £1,000 with a stamp "IOP" on it (plus the name of Isaac Newton, without his permission) is more than $3,000,000 ;-), is talking for 25 minutes about his CV, previous scholarly interests, as well as hot topics in string theory.
Edward Witten is known for having studied some social sciences – journalism, history, linguistics – and being a tool of the Democratic Party candidates (such as George McGovern 1972 who just died) but he has been interested in physical sciences from his childhood. He was interested in astronomy but he was afraid that the job required him to be an astronaut. It is cute to mix astronomers and astronauts. My dad doesn't distinguish astronomers from astrologers.
Of course, his father – a theoretical physicist – was probably affecting Edward Witten, too.
He has been interested in the peace in the Middle East. In fact, some of his $3 million Milner money is going to J Street, a left-wing NGO trying to create peace between the Israeli Arabs and Jews in some of the most naive ways. Of course, just like anyone who takes string theory seriously, he shows an old picture of himself on a camel.
He talks about his wife, kids, and interests. His parents didn't believe in pushing kids too far too quickly. He got a standard theoretical physics education rather soon. Only when he was a postdoc, his maths was getting deeper. Supersymmetry became essential when he was a student. It has played a key role in his research from the beginning.
Some extra remarks are dedicated to Einstein's general relativity, extra dimensions, and unification of all forces. He talks about his negative-energy instability of higher dimensions without SUSY. He paints himself as a relative latecomer to string theory. Of course, it depends whom you compare him with. Witten compares the beauty of the sound of different musical instruments depending on the admixtures of the higher Fourier modes.
In the early 1980s, he realized that the available consistent string vacua failed to violate the left-right symmetry (P and CP). At some moment in 1984, the first superstring revolution explodes and it was the first string miracle that occurred when Witten was watching. That's why it was a signal from the Heaven for him. String theory got much more realistic.
The 1990s are the decade of dualities and M-theory. Who needed the other four string theories, and so on. From that time, he's been intrigued by the application of string/M-theoretical methods to understand issues in "ordinary" established particle physics theories (why positive energy, why confinement, ...). This light that string theory manages to shine upon the established theories is Witten's main reason to be convinced that string theory is on the right track. The elegance with which string theory sheds the light is another reason. Witten still calls our understanding of string theory "the rough draft" but this rough draft has already led to amazing insights and Witten doesn't believe that such a chain of astonishing discoveries has happened by coincidence.
The last reason why string theory seems right to him is that it teaches us new and deeper things about the geometry – including things that surprised mathematicians and inspired those at the frontier. He hadn't expected such a thing when he was young but these insights did materialize. Our confusion has actually helped to develop the new concepts.
A special discussion is dedicated to the big mystery what is the core principle underlying string theory much like the equivalence principle or spatial curvature underlying Einstein's general relativity. What string theory really means? It fascinates him most. But for decades, the theory has been smarter than us and forced us to move in previously unanticipated direction with twists – and that's probably still true today.
Witten isn't actively trying to solve the biggest questions. He says a thing often told by Andy Strominger as well – an important skill in the research is to choose a question small enough so that you have a chance to answer it but big enough so that it is worth answering. The Khovanov issues are mentioned as an example. Witten couldn't understand what the stuff was about – but he did understand it was physics-related (I am not that far). Witten makes it clear he realizes that most string theorists aren't interested in those things but he's independent enough not to care. Of course, there's no guarantee this stuff will be important. He knows that but he suspects it will be important. ;-)
At the end, he compares the string theory research with the discovery of new continents and with finding a treasure underground that we don't fully understand but we see that pieces fit together.
Some fun via Fred S. – a new densest element was just found.