INTRODUCTION.

the same explanation of the phenomenon. He rejects, however, Galileo's explanation of the copper colour of the moon in eclipses During a total lunar eclipse, the moon often appears reddish or "copper" because the Earth’s atmosphere bends sunlight into the Earth's shadow. Kepler and Galileo disagreed on the specific atmospheric physics involved.. Kepler ends by expressing unbounded enthusiasm at the discovery of Jupiter's satellites, and the argument it furnishes in support of the Copernican theory The Copernican theory proposed that the planets revolve around the Sun. Seeing moons orbit Jupiter proved that Earth was not the only center of motion in the universe..

Soon after, in 1611, Kepler published another pamphlet, his Narrative Original Latin title: Narratio de Observatis a se quatuor Iovis satellitibus erronibus ("Narrative of Observations of the Four Wandering Satellites of Jupiter")., giving an account of actual observations made in verification of Galileo's discoveries by himself and several friends, whose names he gives, with a telescope made by Galileo, and belonging to Ernest, Elector and Archbishop of Cologne. Kepler and his friends saw the lunar mountains and three of the satellites of Jupiter, but failed to make out any signs of the ring of Saturn corresponding to the imperfect description of Galileo Because early telescopes were low-powered, Galileo could not see the rings clearly; he famously described Saturn as having "ears" or being composed of three distinct stars..

Kepler had previously published a treatise on Optics (Frankfort, 1604) Original Latin title: Ad Vitellionem paralipomena ("Additions to Witelo"), which laid the foundations for modern optics.. He now extended it to the consideration of the theory of the telescope, and explained the principle of Galileo's telescope; he also showed another combination of lenses which would produce a similar effect. This was the principle of the common astronomical telescope, often called, from this circumstance, Kepler's telescope, though he did not construct it. The account of