'Flaws' in the Sun[edit]
The
cosmology of Galileo's time, based on
Aristotle's Physics, held that the Sun was 'perfect' and unflawed.
[38][39] In 807 A.D. there was a sunspot that was large, and it was seen for 8 days.
[40] The records in this period stated that Mercury caused this spot. Since Mercury is the closest planet to the Sun, its location was unclear, and many argued that Mars could be anywhere. In earlier writings, Ptolemy discussions on sunspots referred to the transit movement of Mercury and Venus. in the twelfth century, Muslim philosopher Averroes's interpretation also discussed the transit of Mercury and Venus. In
De constitutione mundi, Giovanni described a similar phenomenon that his father saw, but it may have been possible that he was describing Averroes's observations.
[40]
Only with the invention of the telescope was it possible for sunspots to be systematically observed. Many who had never seen them found the idea of them morally and philosophically repugnant.
[41] Those who could see them, like Scheiner, wanted to find an explanation for them within the Aristotelian system. Galileo's arguments in
Letters on Sunspots were intended to demonstrate these claims as false; and if they were false, Aristotelian assumptions about the universe could not be true.