1877 - Henry Norris Russell was born.

Russell was an American astrophysicist who is best known for the Hertzsprung-Russell diagram which shows the relationship between star brightness and spectral type. He developed a method to compute the distance to binary star systems and used the light from eclipsing binary stars to calculate their mass. He also described the coupling of electron angular momentum and spin quantum numbers known as Russell-Saunders coupling.

1647 - Evangelista Torricelli died.

Torricelli was an Italian physicist who invented the mercury barometer. He was working on a method to use mercury as a pump and filled a tube with mercury and sealed one end. The other end was submerged into a basin of mercury. The mercury level in the tube dropped down and created a vacuum in the sealed end. He later discovered the level would change as atmospheric pressure changed. The non-SI pressure unit Torr was named in his honor.