Some numbers that suggest a different explanation of how it works, Harry.
N/V number of molecules per cubic centimeters at optimum (0.1 Torr) pressure: 3.4e15.
Collision mean free path of air molecules: 4.5 centimeters
Average molecular speed (c) : 4.0e4 centimeters per second
Number of molecules striking each cm^2 of vanes & globe wall per second : 0.25* c * N/V = 3.7e19
The photons absorbed by the blackened vane surface set it into vibration of greater
amplitude than the shiny side, thus giving a kick of higher energy to the molecules striking it.
This can be demonstrated with salt or sand sprinkled on a radio speaker laid horizontal while you're
listening to rock "music". :-)
The walls of the globe dissipate the heat from the agitated molecules, hence the radiometer is in
effect a Carnot Engine.
Coating the vanes with an alpha emitter (Americium) makes it a nuclear engine.
Frederick
