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Bouncing beads outwit Feynman

A life-size thought experiment machine performs work

12:44pm, June 11, 2010

View a video of the newly designed machine

Researchers have built a machine that harnesses energy from the random motion of bouncing beads to perform work. The machine, a modified re-creation of a system dreamt up nearly a century ago in a captivating thought experiment, dances around physicist Richard Feynman’s dictum that work can’t be extracted from such a system. 

In 1912, Polish physicist Marian Smoluchowski proposed a thought experiment in which tiny moving particles spin a windmill-type paddle, which then spins a toothed wheel. A pawl prevents the wheel from slipping backwards, forcing the wheel to move in one direction only. But as Feynman later pointed out in his famous lectures on physics, the original calculations — which seemed too good to be true — missed something. If everything in the system was the same temperature, the pawl would occasionally slip off the wheel, resulting in no net movement, he showed.

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