The Radiometer - See the energy of Light! 

The radiometer was invented by Sir William Crookes in the mid-nineteenth century to measure the intensity of radiant energy. Glass bulb contains object like a weather vane. 

The Radiometer is a deceptively simple device providing an intriguing introduction to the study of gases, molecular motion, and thermodynamics. An evacuated glass bulb encloses a rotating shaft with vanes painted black on one side, silver on the other. Light energy differentially warms the vanes' flat surfaces, imparting energy to the gas molecules which "kick" the vanes into a rapid rotation. Radiometers may also be described as solar radiometers or UV radiometers.

The Radiometer comes with instruction and explanation sheet.