Editing Tycho Brahe (section)

==== Great Comet of 1577 ====
Tycho observed the [[Great Comet of 1577|great comet]] that was visible in the Northern sky from November 1577 to January 1578. Within Lutheranism, it was commonly believed that celestial objects like comets were powerful portents, announcing the coming apocalypse. Several Danish amateur astronomers observed the object and published prophesies of impending doom. Tycho was able to determine that the comet's distance to Earth was much greater than the distance of the Moon, so that the comet could not have originated in the "earthly sphere", confirming his prior anti-Aristotelian conclusions about the fixed nature of the sky beyond the Moon.{{sfn|Christianson|1979}}

Tycho realized that the comet's [[Comet tail|tail]] was always pointing away from the Sun. He calculated its diameter, mass, and the length of its tail, and speculated about the material it was made of. Through nightly observations of the comet, Tycho Brahe estimated its closest approach to Earth at about 230 times the Earth's radius. He also analyzed its motion, suggesting an orbit located between Mercury and Venus.<ref name=":0">{{Cite journal |last=Yavari Ayin |first=Mostafa |date=2023 |title=Defenseless eyes against the sky. A narrative of some astronomical observations before the invention of the telescope |journal=Nojum Magazine [Iranian Magazine of Astronomy] |volume=32 |issue=4 |pages=36–41}}</ref>

At this point, he had not yet broken with [[Copernican heliocentrism]], and observing the comet inspired him to try to develop an alternative Copernican model, in which the Earth was immobile.{{sfn|Christianson|1979}} Tycho Brahe's comet observations challenged the prevailing theory of solid celestial spheres. With the comet likely traveling between Mercury and Venus, the notion of these rigid spheres became untenable. It suggested a vast emptiness where objects like the comet, potentially quite large, could move freely and exhibit properties unlike those previously understood.<ref name=":0" /> The second half of his manuscript about the comet dealt with the astrological and apocalyptic aspects of the comet. Tycho rejected the prophesies of his competitors. Instead, he made his own predictions of dire political events in the near future.{{sfn|Håkansson|2004}} Among his predictions was bloodshed in Moscow, and the imminent fall of [[Ivan the Terrible]] by 1583.{{refn|1=Ivan the Terrible died a year later than predicted by Tycho Brahe{{sfn|Christianson|1979}}|group=note}}