On this day in 1869, Scottish physicist Charles Wilson, inventor of the Wilson Cloud Chamber, was born. Wilson attempted to re-create in his laboratory the wondrous early-morning cloud effects seen in the Scottish Highlands. He found that charged atoms or ions were needed as nuclei for the condensation of water droplets, overturning the notion that droplets formed around dust particles. In 1911, Wilson produced his cloud chamber, which allowed scientists to see the paths of single charged particles as trails of minute water droplets. The invention was later used to observe and photograph tracks of alpha and beta particles emitted from radioactive materials.
[Source: Trevor I. Williams, Ed., A Biographical Dictionary of Scientists (John Wiley & Sons, ed. 3, New York, 1982).]