Via PZ’s blog Pharyngula I saw this xkcd strip.
I am a physicist and a physics teacher and so of course am well aware of this popular lecture demonstration where a bowling ball or some other heavy object is hung from the ceiling of a lecture hall. A person then stands some distance away from the lowest point at which the ball is resting and brings the ball up to their nose with the rope kept taut. The ball is then released and it swings away from the person and returns, just like a pendulum. The point is whether the person will flinch when they see the ball come back towards their face. The law of conservation of energy predicts the ball will not rise higher than the initial release point and so will never hit the face, and the panel looks at how different scientists might respond to being in that situation.
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