Crookes Radiometer: A Comedy of Errors

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Invented by Sir William Crookes in 1873, this device is also known as a light mill. It is still a popular novelty item. A sealed glass bulb, evacuated to about 1 Pa (~ torr), encloses a set of (usually four) vanes, black on one side, white or silver on the other, that can rotate on a low-friction spindle. When exposed to light or heat, the dark sides rotate away from the source. Conversely, if a block of ice is placed nearby, the vanes rotate in the opposite direction. The mechanism of this phenomenon was a source of scientific controversy for over half a century.
Contributed by: S. M. Blinder (October 2008)
After work by: Sándor Kabai
Open content licensed under CC BY-NC-SA
Snapshots
Details
Snapshot 1: light bulb as heat source; counterclockwise rotation of vanes
Snapshots 2, 3: block of ice causes clockwise rotation
For further details see article in Wikipedia.
Permanent Citation
"Crookes Radiometer: A Comedy of Errors"
http://demonstrations.wolfram.com/CrookesRadiometerAComedyOfErrors/
Wolfram Demonstrations Project
Published: October 3 2008