1984 - Paul A.M. Dirac died.
Dirac was an English physicist who shares the 1933 Nobel Prize in Physics with Erwin Schrödinger for their advancement of atomic theories. Dirac advanced quantum mechanics by deriving a relativistic solution to the electron's wave function. This solution also predicted the existence of antiparticles which would be later detected in the form of positrons. His theories form the basis of quantum electrodynamics.
1972 - Harlow Shapley died.
Shapley was an American astronomer who discovered the Sun's location within the Milky Way galaxy. He placed the Sun near the central plane of the galaxy and 30,000 light years from the galactic center. He also showed Cepheid variables were not paired starts that eclipsed each other, but were pulsating starts.
1942 - Christiane Nüsslein-Volhard was born.

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Nüsslein-Volhard is a German geneticist who shares the 1995 Nobel Prize in Medicine with Eric Wieschaus and Edward Lewis for their discoveries concerning the genetics of early embryonic development. Wieschaus and Nüsslein-Volhard investigated the development of Drosophila melanogaster or fruit fly embryos by causing mutations. They identified the mutations that made changes to embryonic development and identified its location in the fly's genetic structure.
1891 - James Chadwick was born.
Chadwick was an English physicist who was awarded the 1935 Nobel Prize in Physics for the discovery of the neutron. He tried to identify the extra mass of an atomic nucleus by firing alpha particles into a beryllium target and allowing the resulting radiation to interact with paraffin wax. The interactions between the radiation and the hydrogen in the wax led to the discovery of a particle with no charge with the mass nearly the same as hydrogen which he called neutron.
1616 - Thomas Bartholin was born.

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Bartholin was a Danish anatomist and physician who was the first to describe the entire human lymphatic system. He identified the thoracic duct as the entry point for lymphatic fluids to enter the bloodstream. The lymphatic system is an important part of how the body constructs an immune response to infections.