Jul 28, 2008

William Crookes invented his radiometer over 100 years ago, its not new. I've had one of these toys for 20 years from the novelty section of a magic shop. There's a good page on wikipedia explaining how it works and the history: http://en.wikipedia.org/wiki/Crookes_radiometer

Even Albert Einstein had a go at explaining the radiometer. His explanation was that gas molecules hitting the warmer black side pick up heat and speed away, giving the vanes a push. However that doesn't explain the speed with which you can see the vanes move. Osborne Reynolds suggested thermal transpiration where gas molecules move from the cold side of a metal plate to the warm side, creating thrust. Wiki says thatits now believed that both forces move the vanes, but its unknown which is stronger.

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Jul 28, 2008

William Crookes invented his radiometer over 100 years ago, its not new. I've had one of these toys for 20 years from the novelty section of a magic shop. There's a good page on wikipedia explaining how it works and the history: http://en.wikipedia.org/wiki/Crookes_radiometer

Even Albert Einstein had a go at explaining the radiometer. His explanation was that gas molecules hitting the warmer black side pick up heat and speed away, giving the vanes a push. However that doesn't explain the speed with which you can see the vanes move. Osborne Reynolds suggested thermal transpiration where gas molecules move from the cold side of a metal plate to the warm side, creating thrust. Wiki says thatits now believed that both forces move the vanes, but its unknown which is stronger.

Reply