1816 – Gaslight illuminated Philadelphia’s Chestnut Street Theatre, improving on an innovation pioneered in London. Instead of coal the gas was created from pitch, reducing the malodorous vapors caused by the wonder’s creation.
1915 – Albert Einstein presented general theory of relativity to the Prussian Academy of Sciences.
1976 – The Project Viking landers passed through superior conjunction at Mars, enabling scientists to begin an experiment that used the landers as transponders. The data collected confirmed the Shapiro Delay, becoming one of the best confirmations of General Relativity we have seen.
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