In March 1610 a slim Latin pamphlet announced that the universe had changed: mountains on the Moon, countless invisible stars, and four moons circling Jupiter. The Sidereal Messenger is Galileo’s own report of the first telescopic astronomy, translated with notes, and joined here by part of Kepler’s generous, astonished reply.
Few documents in the history of science carry this voltage — eyewitness news from the night the sky got deeper. Download the free EPUB and read the observations that started modern astronomy.