Today’s factismal: On November 13, 1577, Tycho Brahe (and millions of others) saw the “Great Comet” that sparked the heliocentric revolution.
History is a funny thing. The littlest incidents can cause the greatest conflicts while much larger events have almost no effect. Perhaps the best examples of this are the views of the heavens afforded to Tycho Brahe in 1577 and to Galileo Galilei in 1610. Both of them provided us with important scientific discoveries, but only one changed the way we view the universe.
In ancient history, comets were regarded as disasters – literally! “Disaster” means “bad star” and a comet was thought to be a star that had fallen from its place in the heavens. And so they were regarded with a mixture of fear and awe when they appeared. But in 1577 one showed up that was so spectacular and seen by so many people that it redefined how we saw comets; it soon became known as the Great Comet of 1577. Among those who saw it was the astronomer Tycho Brahe, who was already famous for his description of the nova of 1573 which proven that the heavens weren’t unchanging and for his theory that the Sun revolved around the Earth and the other planets revolved around the Sun. Thanks to his fame, Brahe had been given an amazing observatory that he used to make very careful measurements of the comet.
One of his most important observations was that the comet’s tail always pointed away from the Sun. Though it would take astronomers another three centuries to explain why that happens (because the tail is made of ionized gasses being pushed away by the solar wind), his observation helped to demystify comets. And his observations of the path that the Great Comet of 1577 took helped his helper/amanuensis/minion (depending on whom you asked) Johannes Kepler to decipher how planets moved. And that, in turn, provided the death knell to the geocentric universe (which was the opposite of what Brahe had hoped would happen).
But before Kepler finished his work, Galileo did his. Among the many things that he discovered with the telescope he invented were the rings of Saturn. His telescope was just good enough to see that they gave Saturn a “jug-eared” appearance, which he promptly bragged about to everyone. Unfortunately for Galileo, Saturn’s rings don’t always look the same. As the planet moves around the Sun, the rings apparent tilt changes so that they get larger and smaller and sometimes vanish completely. Naturally, it was during one of these complete disappearances that Galileo’s detractors took a look for themselves. When they didn’t see the “jug ears”, they said that Galileo was making up all of his evidence and used that to condemn him. It would take the more detailed (and less insult-filled) work of Brahe and Kepler before the heliocentric universe would become accepted.
Of course, the great Comet of 1577 wasn’t the last comet to swing by the Sun. Right now, there is a spacecraft that has actually landed on a comet and will ride it around the Sun, capturing data (and pretty pictures and eerie music) the whole way. And there are literally dozens of other comets that dive-bomb the Sun each day. If you’d like to learn more about comets (and maybe identify a few yourself), then head over to SOHO’s Comet Hunting page: