Friday, February 10, 2006

My Favorite Planet

I just finished Dava Sobel’s The Planets, which is a cute little book for light reading. Sobel writes for the crowd that wants a little literary feeling, but nothing too heavy: she exploits alliterative phrasing and little devices, including writing one chapter as a first-person account as ALH84001, the famous Marian meteorite.

The literary swamped the scientific, though, in her chapter on Jupiter, and I found this distressing because it’s my favorite planet. Sobel’s theme in this chapter is astrology: she tells the horoscopes of Galileo the astronomer as well as Galileo the spacecraft, all of which is cute and so forth, but never does she stop and say clearly that astrology is idiotic crap to which nobody should give a second’s worth of serious attention. I don’t imagine that Sobel really believes in astrology, but from this chapter you wouldn’t know it, and I fear that foolish people will find here the sort of thing that they long for: vindication of their superstition.

Jupiter is so much more interesting than that, though. It’s more than ten times the diameter of Earth, yet it rotates completely in only ten hours. Parts of it, that is—because some of its cloud bands spin one way and other cloud bands spin the opposite way, which is partly responsible for the tremendous storms we can see. Yet the storms never waver out of their latitudes, always remaining in the same predictable place, for centuries, in the case of the Great Red Spot. Jupiter’s core is metallic hydrogen, a super-compressed variety of the element that can’t be produced on Earth for more than an instant. The tremendous speed of this metallic core generates an enormous magnetosphere—a magnetic envelope surrounding the planet that, if you could see it, would be as large in our sky as the Sun is. This magnetic field is so strong that space probes are physically shaken by it when they enter it. Worse, it is tearing Jupiter’s moon Io apart, atom by atom, creating a huge torus of dust that’s been stripped off of the moon—which contains the only known active volcanoes other than Earth’s. The electricity generated by Io’s flight through the magnetosphere is beyond belief: 400,000 volts. Meanwhile, the tremendous pressure on Jupiter, and its exotic materials, make for some of the most fascinating weather patterns ever seen, incluing gigantic lightning bolts far beyond anything Earth knows. Earth itself was even dwarfed by the explosions of comet Shoemaker-Levy 9; each of its impacts on Jupiter were the size of several Earths. How can someone not love this planet? And, probably the best of all, when Galileo dropped a probe into the atmosphere, the information it relayed to us before its eventual destruction demolished almost every previously held theory about the planet’s nature.

How can someone not love this amazing planet?