http://www.ted.com Leonardo Da Vinci’s life and work is well known — but his own face is not. Illustrator and activist Siegfried Woldhek used some thoughtful image-analysis techniques to find what he believes is the true face of Leonardo. Here, he walks viewers through exactly how he did it.

http://www.ted.com Clifford Stoll could talk about the atmosphere of Jupiter. Or hunting KGB hackers. Or Klein bottles, computers in classrooms, the future. But he’s not going to. Which is fine, because it would be criminal to confine a man with interests as multifarious as Stoll’s to give a talk on any one topic. Instead, he simply captivates his audience with a wildly energetic sprinkling of anecdotes, observations, asides — and even a science experiment. After all, by his own definition, he’s a scientist: “Once I do something, I want to do something else.”