One of William Crooke's original radiometers

Crookes radiometer, 1877.
In the 1870s William Crookes conducted a series of experiments on vacuums which led him to invent the radiometer. They became popular immediately, although the explanation of why the vanes turn was contested for a long time.
 
Currently on display in:
Making the Modern World
Year made :
c1875
Inventory number :
1888-166_1