The Mechanism Driving Crookes Radiometers

The vanes of a Crookes radiometer rotate when exposed to light. Despite its long history, the mechanism behind this rotation remained a mystery for over a century. Numerous theories were proposed, but none could fully explain all the observations, particularly the rapid initial acceleration and the backward rotation when cooled. Our investigations into the driving mechanism of radiometers have led to the discovery of a novel type of interaction between molecules, termed transimpact. When an electron in an atom absorbs energy, it excites to a higher orbital, expanding the electron cloud of the atom while reducing the distance to adjacent atoms within a few nanoseconds. This sudden reduction in space between atoms disrupts the balance of forces, creating a repulsion between the atom and surrounding particles. When transimpacts occur between air molecules and molecules on the surface of a radiometer vane, the air molecules can be pushed away with significant momentum, similar to the burst of popcorn, propelling the vane in the opposite direction. The black side of a vane, being more efficient at absorbing energy, results in more electron excitations and transimpacts than the white side. This unbalanced impact between the two sides causes the vanes to rotate. Because atomic electron transitions occur instantaneously upon exposure to incident light, the transimpact theory predicts a decreasing acceleration profile marked by an initial peak, resulting from increasing air drag as rotational speed increases. This distinctive feature sets the theory apart from all existing models. To test this prediction, a series of experiments was conducted. The close alignment between theoretical projections and experimental results provides compelling evidence in support of the transimpact theory.