Aristotle's Supernova

As long as the heavens had been changeless, there had been little reason to dissent from aristotle's claim that comets were atmospheric. This super nova was bright enough you could see it in the daytime. It got tycho wondering about the immutability of the heavens because they don't seem very changeless. And by taking different readings and triangulating, tycho could figure out how high up a comet really was.