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In the Channel 4 programme Breaking the Science Barrier (1996), Richard Dawkins faces down a pendulum:

This is a classic example of a “put your money (or nose) where your mouth is” physics demonstration. It also appears in Carl Sagan’s novel Contact (1985), for example, and Feynman did it during the freshman physics lectures he gave at Caltech.

Later in the same show, Dawkins interviews Douglas Adams, and gives a few comparisons to help understand the depths of evolutionary time:

(Props to Sean Carroll.)


  1. Can’t watch the video right now… but I wanted to point out that Walter Lewin does something similar with a pendulum in his freshman physics lectures as well. (I can’t find it right now, but I definitely remember seeing it back when I spent some time watching those videos in December.)

  2. He uses himself as a pendulum bob at the end of lecture 10, and the staring-down-harmonic-death demonstration is at the end of lecture 11.

    Dang, there are more goodies on OpenCourseWare every time I look.

  3. I love how Dawkins picks a girl to play Jesus…you can just sense the pleasure it gave him when he made that decision.

  4. There’s the (probably apocryphal) story that a professor did the pendulum demo in class, standing up against a wall, and got a student to give it a try. What went unnoticed was that the student gave the ball a little push, rather than just letting it go …

  5. “Arrr. The laws of science be a harsh mistress.”

  6. What went unnoticed was that the student gave the ball a little push, rather than just letting it go …

    That’s the part that would worry me (and why I would insist on releasing the pendulum myself). Ditto for fire-walking. You can “prove” that the pendulum won’t hit you, or your feet won’t burn, using a mathematical model of the situation — but the real world tends to include, um, perturbations that often make things come out a bit differently.

  7. It just occurred to me that one reason why a clumsy fellow like myself should go for the pendulum instead of the fire-walking is that, by conservation of energy, the pendulum can’t come back to hit you more strongly than you accidentally pushed it.

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