Radiometer

Bird in Hand Verified independent store

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Invented in the 1870s by Sir William Crookes, the radiometer was quickly the center of controversy among scientists. WHAT IS MAKING THE VANES MOVE? Crookes hypothesized that light particles were "pushing" the vanes, but abandoned this reasoning once the vanes moved not due to just light, but hot and cold sources of radiant energy. Today, we know the vanes moved based on the principle of Thermal Transpiration. Simply put, changes in temperature of the gases inside create an unequal balance in pressure between the black side of the vanes and the white sides, therefore the vanes are PUSHED into the area of lower pressure. Gases must always find equilibrium, so the radiant energy causes the movement of the vanes. This is not a toy. Made of glass. Please handle with care. ⚠️WARNING: This product can expose you to BBP (Butyl benzyl phthalate), which is known to the State of California to cause birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. Show more