“Oh thick wits. Oh blind watchers of the sky.” This is the tone with which Tycho Brahe, the greatest naked-eye astronomer to ever live, began his landmark work, De Nova Stella, On the New Star*. It was this work that coined the modern term “nova” and later earned the naming of “Tycho’s Supernova”, which I have chosen as the 9th object in my top 10 favorites countdown. Around 9,000 years after the supernova explosion occurred, its light first arrived at Earth in November of 1572. It appeared beside the constellation Cassiopeia, The Queen, and at its peak brightness was visible even during the day.
On seeing the nova for the first time, Tycho wrote: “I was so astonished by this sight that I was not ashamed to doubt the trustworthiness of my own eyes. But when I observed that others, on having the place pointed out to them, could see that there was really a star there, I had no further doubts.” He was so impressed by the sight that he would devote the rest of his life to astronomy, and by excruciatingly careful observations, would be the first to meaningfully undermine the notion of the immutable heavens. For at the time, it was almost universally accepted that the stars and planets were eternally unchanging. To suggest otherwise would not just challenge prevailing opinions, but also the theology of the day.
And so the thinkers of the late 1500’s deemed the new star a “tailless comet”, a mere atmospheric effect. Comets in those days were thought to be combustions in the upper atmosphere, as were any unexpected dynamics in the night sky. Since the heavens were assumed to be changeless, the only possible explanation left was in the atmosphere. But Tycho realized that if this were true, then he should observe a parallax, a slight shift between dusk and dawn in the position of the nova with respect to the background stars, which depends on the distance between object and observer. Such a shift is observed for the Moon, so when Tycho found no parallax, he rightly concluded that the new star must be at least more distant than the Moon.
He also found that the object moved in perfect synchronization with the stars, and eventually decided that this was no atmospheric effect. Rather, it truly was a new star and a major upheaval in our understanding of the cosmos. As you might expect, this idea was not met with open minds, and thus we return to the insult in the preface of his book. A tame response from Tycho, though, who was a man willing to literally die defending the integrity of his ideas. He once lost much of his nose to a sword duel fought over the legitimacy of a mathematical formula. Admirable or foolhardy, you decide.