Modelle des Kosmos: Vorstoss ins Unendliche
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.