Scottish physicist Charles C. T. R. Wilson, from the summit of Mount Nevis, the highest mountain in the British Isles, took meteorological measurements for two weeks to study clouds and their formation. Upon returning to Cambridge, he conducted several confirmatory experiments. He then realized that when air expands due to a drop in pressure at altitude, it becomes supersaturated. Under the right conditions, the moisture in the air then condenses around small dust particles or ionized particles. Fifteen years later, Wilson became the first to observe the motion of individual alpha or beta particles in a cloud chamber he had specially invented.
