The Day the Universe Changed - James Burke [68]
Stevin’s practical work included proposals for mills and sluices as well as navigation, all matters of particular interest to the Dutch. In 1585 he began developing calculation techniques that would help solve the problems involved in applying terrestrial experiments to planets in the sky. He published the first systematic explanation of the use of decimal fractions and the application of decimals in weights and measures.
Stevin’s famous ‘wreath of spheres’ and motto, on the title page of The Elements of the Art of Weighing.
In 1585 he produced a major work on mathematics and algebra. A year later he wrote The Elements of the Art of Weighing, in which he provided a good example of his desire to make things plain even to the non-mathematically inclined. He showed that if you took a necklace of metal spheres and laid it over a triangle, apex up, of which one side was longer than the other, the necklet would hang on the triangle. Then, by taking away all the spheres hanging below the triangle, you would leave only those resting on the two inclined faces. These would remain in position, even though on the short, steep side there were only two, and on the long, shallow side there were four. This was due to the relation between the downward forces on either side being in equilibrium, thanks to the differing angle of their support. This resolution of different forces is known today as the parallelogram of forces.
Above the illustration of this experiment, Stevin put his scientific motto: ’ Wonder en isgheen wonder’ (nothing is the miracle it appears to be). The ‘wreath of spheres’, as it was called, gave the astronomers evidence that the forces acting on a planet could be such as to keep the planet in a stable condition as it moved.
All this was, of course, guesswork until mathematical speculation could be replaced by proof that the heavens were not as the Church described them. This was a matter that was about to engage Galileo’s rapt attention and turn him from a maths professor with a comfortable though obscure position into a household name throughout the Continent. The event, when it happened, would also confirm the fears of his friends that when he had gone to Florence in 1610 it had been to a place ‘where the authority of the friends of the Jesuits counts heavily’.
It was there in Florence that Galileo wrote the twenty-four pages which were to begin his downfall. In the previous year he had heard of a new ‘looker’ invented by a Dutchman called Lippershey. By mid-year he had developed it to the point where his looker-telescope would magnify a thousand times and make things appear thirty times closer. The first time he looked through it at the moon he claimed he could see a planet like the earth, with mountains and ‘seas’. And yet, as a heavenly body, the moon was supposed to be perfect and without irregularities. He looked at the stars. Through the telescope they appeared no bigger, only brighter, suggesting that they were an immense distance away. There were, however, vastly more of them than Aristotle had said. The Milky Way, in particular, seemed to be made up of millions of stars in clusters which he called ‘clouds’ (nebulae).
On 7 January 1610 Galileo was looking at Jupiter with his best telescope when he noticed three new stars he had not seen there before, two to the east and one to the west of the planet. The next night they were all to the west, in a line. Jupiter’s movement at the time was such that if these were stars, Jupiter should have moved against them and revealed them all to the east of the planet. Throughout the winter Galileo observed these tiny stars and became