Family and friends contribute to a celebration of Richard Feynman, one of the most inspiring and influential scientists of the 20th century. Feynman, who died 25 years ago, helped design the atomic bomb, won a Nobel Prize for Physics and solved the mystery of the Challenger shuttle catastrophe.

I had many types of out -of-the-body experiences. One time, for example, I could "see" the back of my head, with my hands resting against it. When I moved my fingers, I saw them move, but between the fingers and the thumb I saw the blue sky. Of course that wasn't right; it was a hallucination. But the point is that as I moved my fingers, their movement was exactly consistent with the motion that I was imagining that I was seeing.