On 19 April 1610, after reading Galileo's Sidereus Nunsius, Kepler wrote to Galileo:

tuam, Galilaee, machinam, qua caelum ipsum terebrasti

Your device, Galileo, with which you even drilled the heavens

Galileo not only gazed at the depth of the heavens, he also began a systematic record of his observations.

The four little stars in the drawing from Sidereus Nuncius denote the positions of the newly discovered moons around Jupiter in snap-shot form.


Galileo Galilei, Sidereus Nuncius

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