1984 - Martin Ryle died.

Ryle was a British radio astronomer that shares the 1974 Nobel Prize in Physics with Antony Hewish for his invention of the aperture synthesis technique. He developed this interferometer technique to resolve weak radio signals from stellar sources. This allowed astronomers to discover galaxies further away than was ever seen before.

1940 - Heinrich Kayser died.

Kayser was a German physicist that worked with Carl Runge to determine the spectra of many chemical elements. During these investigations, he discovered the presence of the element helium in the Earth's atmosphere. This was the first instance where helium was discovered outside the Sun's spectra. He and Runge developed an empirical mathematical formula to explain the grouping of spectral lines independently of Johannes Rydberg.

1914 - Raymond Davis, Jr. was born.

Davis was an American physicist who shared half the 2002 Nobel Prize in Physics with Masatoshi Koshiba for the detection of cosmic neutrinos. Davis attempted to detect neutrinos by investigating the process of reverse beta decay. Reverse beta decay occurs when a neutrino interacts with just enough energy with a nucleus of a stable isotope and creates a radioactive isotope.

1840 - Friedrich Wilhelm Georg Kohlrausch was born.

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Kohlrausch was a German physical chemist who focused on the thermal, electrical and magnetic properties of electrolytes. Electrolytes are substances that conduct electricity in solutions through the transfer of ions. He was the first to demonstrate electrolytes have a constant electrical resistance and measured the velocities of the transferred ions for a particular electrolyte.