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Galileo's Lunar Observation

In 1610, Galileo dated his first letter describing telescopic observations in which he saw the moon's cratered surface using his twenty-powered spyglass. He wrote, “... it is seen that the Moon is most evidently not at all of an even, smooth, and regular surface, as a great many people believe of it and of the other heavenly bodies, but on the contrary it is rough and unequal. In short it is shown to be such that sane reasoning cannot conclude otherwise than that it is full of prominences and cavities similar, but much larger, to the mountains and valleys spread over the Earth's surface.” Galileo went on to describe the phenomena in considerable detail, rehearsing, as it were, the observations and conclusions he was to publish more elaborately a few months later in Sidereus Nuncius.

Books in our collection

Discoveries and opinions of Galileo  by Galileo Galilei

The essential Galileo  by Galileo Galilei and Maurice Finocchiaro

Galileo and 400 years of telescopic astronomy  by Peter Grego and David Mannion