Watch light energy come alive right in front of your eyes! No batteries or electricity needed! It's the spear powered by the sun! When light strikes the veins it transfers heat to each one, but not to the same degree. The light wing reflect the rays and the darker wing absorbs the rays. The stronger the light the more energy there is to heat up the darker side causing the wings to spin faster.

Sunlight spin this radiometer's 4 veins. The stronger the light the faster they spin.

Vacuum sealed globe on a durable plastic base. Explore light and physics.

Measures: W: 3.5" H: 5" D: 3.5" Weight: 10oz