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No that’s not a typo; it's a message Galileo sent to the brilliant German astronomer Johannes Kepler. And it led to the enduring belief that Mars possessed two moons, centuries before they were actually discovered.
Galileo was an observer, using his newly built telescope to sweep the skies and look at things no human had seen before. He saw the mountains on the Moon, the phases of Venus and the stars of the Milky Way. Kepler was a theoretician, gifted in mathematics. He had already performed a feat nobody had ever done by describing planetary motion in mathematical terms. At a stroke he had proved that the heavens were not the mysterious, unknowable realm of God that many believed.
When Kepler received the string of letters from Galileo, he knew at once that it was a coded discovery and he set about unscrambling the anagram. Galileo had already announced the discovery of four moons at Jupiter, and Kepler’s analytical mind had formed a hypothesis. If Earth had one moon and Jupiter had four, then Mars should have two moons based upon the geometrical progress where you double the previous number to gain a series (1, 2, 4, 8 etc.).
Johannes Kepler
Kepler wrestled with the anagram until he squeezed out "Salve umbistineum geminatum Martia proles." He called it a barbaric verse, and it was a letter different from the original but it served his conviction that Mars had two moons. Kepler's translation reads: "Be greeted, double knob, children of Mars." Imagine reading that in a scientific journal today!
In fact, Kepler was wrong. Galileo had caught a blurry glimpse of the rings of Saturn and had written: "Altissimum planetam tergeminum observavi" meaning "I have observed the highest of the planets three-formed."
Nevertheless, the conviction that Mars had two moons persisted for centuries. In 1726, English satirist Jonathan Swift wrote about them in Gulliver's Travels. But it wasn’t until 1877 that Asaph Hall discovered Phobos and Deimos, the two moons of Mars, from the United States Naval Observatory in Washington DC. -- Stuart
18-02-2010 • 18:16:02
Yes, u and v were interchangeable well past Kepler's time.
Copernicus: since Copernicus's orbits were circular, his model wasn't very good at making observational predictions. That needed Kepler and his elliptical orbits. Anyway, I think the article is referring to Kepler's Laws.
14-02-2010 • 02:15:52
I think Kepler could be forgiven for his mistake, considering that u and v were still apparently interchangeable in Latin! Thanks for a fascinating article.
18-02-2010 • 13:28:45
Hello,
you wrote "He had already performed a feat nobody had ever done by describing planetary motion in mathematical terms. At a stroke he had proved that the heavens were not the mysterious, unknowable realm of God that many believed."
I'm sorry, but isn't that a false statement: but I think Copernicus was the first in "describing planetary motion in mathematical terms".
PS Please excuse my English - I'm not a native speaker.
19-02-2010 • 17:01:54
Thank you for your interest in the blog, and for your comment.
Although Copernicus suggested that the Sun was the centre of the Solar System he continued to believe that planets moved in circular orbits. This meant he had to assume a complicated pattern of circles on top of circles, known as epicycles.
Each planet needed a different arrangement of epicycles, and even then the observed motion of the planets could not be well reproduced.
Kepler showed that by letting go of the assumption planets moved on circular orbits, he could reproduce their motions accurately. The key was that each planet followed an elliptical orbit. As a result, Kepler could distil the motion of all planets into just three mathematical laws – the first time the general principles of planetary motion had been understood.
Hope that’s clearer!