Thursday, September 27, 2012

Man in the Middle

There's a chain of scientists and astronomers, from Copernicus to Newton, who figured out how the Solar System works. Today (September 28th) is the birthday of a guy who frequently gets left out of the chain, namely because he got part of the workings right and another part of it completely wrong. So, let's focus on him a little bit too much now, shall we?

Ismaël Boulliau, or Ismaël Bullialdus as he's called in his writings, was a French guy born in 1605. He was from a Calvinist family, so that meant he didn't have to worry too much about upsetting Papal authorities with new ideas about the heavens. His dad, an amateur astronomer, got young Ismaël interested in the latest theories about orbits and planetary motion.

Despite his Calvinist upbringing, Ismaël converted to Catholicism and became a priest at age 26. Fr. Bullialdus wound up working in the Royal Library in Paris, reading, sorting, and purchasing books for Louis XIII's court. King Louis was big on funding the arts and sciences, so Fr. Bullialdus was a busy guy for library acquisitions.

Ismaël continued the astronomy studies sparked by his father, and due to his position in the upper ranks of the government, became friends with other astronomers and mathematicians such as  Christiaan Huygens, Blaise Pascal, and Pierre Gassendi (all of whom were visitors to the royal court).  These men were on the cutting edge of planetary motion theories, and their correspondence shaped the investigations made by astronomers throughout Europe.

One of the hottest theories about planetary motion was made by a fellow astronomer in Germany at about the same time all these French guys were writing each other. Johannes Kepler figured out that the planets didn't move in circles around the Sun (as the astronomer Copernicus had theorized) but in a path of ellipses, with the Sun located on one focal point of the ellipse. Kepler wasn't sure what force caused the planets to move around the Sun in this manner, but he was pretty certain that the force was inversely proportional to the distance of a planet to the Sun.

Fr. Bullialdus was intrigued, but Kepler's numbers didn't add up. It seemed as though this mysterious force (if it did exist) would operate similar to how light and sound did with distance: namely, that the force would fade not by the inverse of the distance, but by the inverse of the distance, squared. When Bullialdus plugged in the numbers using his own formulas, the motions seemed to work just fine. Fr. Bullialdus published his findings in a book he called Astronomia philolaica, which appeared in 1645.

So, in 1645 Bullialdus had written this book that accurately described the motions of the planets. Unfortunately, he spent the second half of the book refuting the idea that some kind of "force" existed to make the planets go around the Sun. Instead, Ismaël believed the Sun and the planets were rolling around in the sky because of their initial trajectories at the beginning of the Universe. Fr. Bullialdus wrote, "I say that the Sun is moved by its own form around its axis, by which form it was ignited and made light, indeed I say that no kind of motion presses upon the remaining planets." Despite mathematical evidence to the contrary, he refused to apply the clues to discover the laws of gravity.

Thirty-eight years later, Sir Issac Newton would take the clues left by Bullialdus in Astronomia philolaica in order to shape his own book, the Principia Mathematica. Newton noted in the foreword to his book that Bullialdus's math was right on the money. However, Newton (and rival Robert Hooke) both managed to take the next step and specify that gravity was a predictable force in the Universe.

Tough break for Fr. Bullialdus. He retired to Abbey St. Victor, where he lived out his final years as a simple priest. On the plus side, today he's got a crater named after him - - if you have clear skies tonight, the sunlight should just be hitting his crater in the middle of the Sea of Clouds. Easy to spot - it's got a tiny peak in the middle that casts a shadow on lunar mornings.  So, maybe go out and take a look at the Moon tonight, and think of the fellow who had all the pieces, but didn't solve the puzzle.

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