On this day in 1631 - November 7th - French priest and astronomer Pierre Gassendi observed a transit of Mercury.

Johannes Kepler had predicted transits of Mercury and Venus, but when Gassendi witnessed a transit of Mercury, he was the first person to see such a transit. There was a transit of Mercury in November 2019, but the next one doesn't occur until November 13, 2032.

Mona Evans
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