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By Root 1042 0

Duke Orsini, Benedetti worked to find out what was wrong with the impetus theory and the concept of circular movement. The first thing he did was reject the Aristotelian idea that things went to some kind of ‘preferred place’, falling faster and faster towards the lowest possible position. Benedetti concentrated on what had happened to an object being projected, rather than what was about to happen. He noticed that if a stone being swung round at the end of a rope were released it flew off in a straight line at a tangent to the circle it had been following before. So impetus obviously caused things to move in straight lines as well as circles. What was more, the way the projected object then fell to the ground showed that impetus did not rob the object of whatever condition made it fall.

In all this Benedetti failed to receive the recognition his efforts deserved. His ideas were stolen by a Frenchman called Jean Taisnier, and for a further two hundred years Benedetti’s name was unknown, although his work, plagiarised by Taisnier, won wide acclaim. The value of all the stone-dropping and cannon-firing, however, was soon to be publicly tested. In the night skies of late 1572 a nova blazed silently in the constellation of Cassiopeia, stupefying the entire continent. The star was so bright that it could be seen by day, and it burned for two years before fading.

The medal struck to commemorate the great comet of 1577. This was the comet which Brahe found to be in an elliptical orbit and which led him to suspect that the crystal spheres did not exist.

Uraniborg, Brahe’s observatory on Hven. Two cupolas protecting the underground observation posts can be seen to the right and left.

The appearance of the new star shook Aristotelian cosmology to its foundations. To begin with, if the heavens were perfect and unchanging, and if God had ended his labours on the seventh day with Creation complete, where did the star come from? Moreover, since it gave no evidence of parallax, the object had to be an incredibly great distance beyond the outer sphere. The position of the Church was being undermined before the eyes of academic and peasant alike, in spite of the fact that some astronomers tried to show that the nova had to belong to the earthly sphere, simply because in Aristotelian law that was the only place where things could change. The nova, they insisted, was something to do with meteorology, a phenomenon like a rainbow. The problem of parallax persisted, however.

It was a Dane called Tycho Brahe who voiced what everybody was thinking. At the end of 1572 when the nova became visible, Brahe was twenty-six years old. He had spent most of his time since the age of sixteen observing, and was for a while at the astronomical centre of Augsburg, in Germany. Just after he returned home he saw the nova. Brahe had always been convinced that astronomy would only progress through highly accurate observation. His own techniques involved the use of massive quadrants which enabled him to measure celestial positions ten times more accurately than any other astron omer. This accuracy provided the irrefutable evidence that the heavens had definitely changed and that Aristotle was wrong.

When, in 1573, he published his comments in a book called The New Star, the King of Denmark was so impressed that he gave Brahe the feudal lordship of the island of Hven, lying between Denmark and Sweden. Here Brahe promptly built a baroque castle which he named Uraniborg, engaged numerous assistants, and continued his observations with even greater accuracy. He was, in fact, to spend the next twenty years observing everything in the sky, all night, every night.

Four years after he had moved to Hven, Brahe’s suspicions about Aristotelian cosmology were confirmed by the appearance of the great comet of 1577. Comets had hitherto been regarded as being part of the earthly, sublunar world, appearing in the atmosphere much as rainbows did. Brahe observed from the small parallax it showed that this comet was much closer than the nova. But the shift of the parallax