May 19

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  1743: Physicist, mathematician, and astronomer Jean-Pierre Christin publishes the design of a mercury thermometer based on the Celsius scale. The Thermometer of Lyon will be built by the craftsman Pierre Casati using this design.

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  1903: Bacteriologist Ruth Ella Moore born. She will research tuberculosis, immunology and dental caries, the response of gut microorganisms to antibiotics, and the blood type of African-Americans.

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  1918: Physicist, historian, and academic Abraham Pais born. Pais will be an assistant to Niels Bohr, and a colleague of Albert Einstein, and later write books documenting the lives of these two great physicists and the contributions they and others made to modern physics.

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  1961: Venera 1 becomes the first man-made object to fly-by another planet by passing Venus (the probe had lost contact with Earth a month earlier and did not send back any data).

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  1971: The Soviet Union launches the Mars 2 spacecraft. The spacecraft will reach Mars, but the landing module will crash after failing to deploy its parachute.

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  2017: Soviet Air Defense office Stanislav Yevgrafovich Petrov dies. Petrov became known as "the man who single-handedly saved the world from nuclear war" for his role in the 1983 Soviet nuclear false alarm incident.

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  2017: Dennis Paulson of Mars remembers the forty-sixth anniversary of the Mars 2 launch, observing a moment of silence for the failure of the mission.