text: With it, he saw that whatever shape he made the hole, the sun's image always remained circular.He also noted that increasing the distance between the aperture and the image surface magnified the image.Chance and spontaneity According to Aristotle, spontaneity and chance are causes of some things, distinguishable from other types of cause such as simple necessity.Chance as an incidental cause lies in the realm of accidental things, "from what is spontaneous".There is also more a specific kind of chance, which Aristotle names "luck", that only applies to people's moral choices.Astronomy In astronomy, Aristotle refuted Democritus's claim that the Milky Way was made up of "those stars which are shaded by the earth from the sun's rays," pointing out partly correctly that if "the size of the sun is greater than that of the earth and the distance of the stars from the earth many times greater than that of the sun, then...the sun shines on all the stars and the earth screens none of them." He also wrote descriptions of comets, including the Great Comet of 371 BC.Geology and natural sciences Aristotle was one of the first people to record any geological observations.He stated that geological change was too slow to be observed in one person's lifetime.The geologist Charles Lyell noted that Aristotle described such change, including "lakes that had dried up" and "deserts that had become watered by rivers", giving as examples the growth of the Nile delta since the time of Homer, and "the upheaving of one of the Aeolian islands, previous to a volcanic eruption."' Aristotle also made many observations about the hydrologic cycle and meteorology (including his major writings "Meteorologica").