November 7, 2021
Today in 1631, Pierre Gassendi made the first observation of Mercury transiting the Sun. He observed the transit by projecting the Sun’s image on a screen of paper. He recorded this in Mercurius in sole visus (1632; Mercury in the Face of the Sun) as support for the new astronomy of Johannes Kepler.
Time-lapse image of the 2003 Mercury transit as observed by NASA’s SOHO spacecraft. Credit: NASA/SOHO