| [1597] Galileo writes to Kepler, " "Like you, I accepted the Copernican position several years ago and discovered from thence the causes of many natural effects which are doubtless inexplicable by the current theories." |
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| [1609] Galileo learns of a "spy glass" made by a Dutch eyeglass maker that magnifies distant objects. Galileo constructs several models of the device and displays an 8X telescope at the Venetian Senate. Johannes Kepler publishes his first two laws of planetary motion. |
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| [1610] Galileo builds a 30X telescope. He then uses it to make several important astronomical discoveries, including four moons of Jupiter, the ring of Saturn, the phases of Venus, and craters and mountains of the moon. His observations of moons revolving around Jupiter confirm for him the correctness of the Copernican model. Galileo also concludes from the irregular features of the moon that the moon is composed of matter similar to that of earth. In 1611, he observes sun spots. |
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