Tag Archives: Celestial Immutability

November 11, 1572

Tycho Brahe

On this date, the Danish nobleman, astrologer, and alchemist Tycho Brahe observed (from Herrevad Abbey) a very bright star, now named SN 1572, that had unexpectedly appeared in the constellation Cassiopeia.  Since it had been maintained since antiquity that the world beyond the orbit of the moon, i.e., the world of the fixed stars, was eternal and unchangeable (a fundamental axiom, known as “celestial immutability”, of the Aristotelian world view), other observers held that the phenomenon was something in the Earth’s atmosphere.  Tycho, however, noticed that the parallax of the object did not change from night to night, suggesting that the object was far away.  He argued that a nearby object should appear to shift its position with respect to the background.  Tycho published a small book, De Stella Nova (1573), thereby coining the term nova for a “new” star (we now know that Tycho’s star in Cassiopeia was a supernova 7500 light years from Earth).  He knew the cosmological ramifications of his discovery and was strongly critical of those who dismissed the implications of the astronomical appearance, writing in the preface to De Stella Nova: “O crassa ingenia. O caecos coeli spectatores” (“Oh thick wits.  Oh blind watchers of the sky”).

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