Saturday, May 5, 2012
astro picture for the day
NASA/Cassini spacecraft picture of a Saturn moon, Helene. This moon is 1) strikingling different looking from many other such moons and asteroids, and 2) positioned at a Saturnian "Lagrange" point. A lagrange point is a stable point, or a balance point with respect to two sufficiently large gravitational bodies. At such a lagrange point, a sufficiently small mass can stay at that point of orbit.
In 1773, Pierre Laplace showed that Jupiter and Saturn periodically(as oppossed to chaotically, or randomly) accellerate and decelerate with respect to one another . . . every 929 years.
I'm not sure when mathematical astronomer's figured out/learned of planets getting phase locked with respect to each other or to the sun. The moon s phase locked to the Earth; you always see the same side of the moon! We never saw the other side of the moon till like 1959 when the Soviet Union launched the first spacecraft to orbit the moon! Venus and Mercury are phase locked to the sun; All thse things, lagrange points, phase locked moons, patterns in the orbits of planets of the solar system; these are not things that one can see; you have to mathematically derive them. People didn't note that the moon never rotates till the mathematical consciousness developed enough; these are just some of the wonders found by celestial mechanics over two hundred years ago!
There were pheonomenon of clocks synchronizing to each others beats(if you hung them on the same wall). All these mechanical marvels and astronomical problems led to much analyses(mathematicians word for calculus and the various generalizations of it).