Broca's Brain - Carl Sagan [113]
From the comparison of asteroidal and meteoritic properties, from laboratory studies of meteorites and computer projections back in time of asteroidal motions, it may one day be possible to reconstruct asteroid histories. Today we do not even know whether they represent a planet that was prevented from forming because of the powerful gravitational perturbations of nearby Jupiter, or whether they are the remnants of a fully formed planet that somehow exploded. Most students of the subject incline to the former hypothesis because no one can figure out how to blow up a planet—which is just as well. Eventually we may be able to piece together the whole story.
There may also be in hand meteorites which do not come from asteroids. Perhaps there are fragments of young comets, or of the moons of Mars, or of the surface of Mercury, or of the satellites of Jupiter, sitting dusty and ignored in some obscure museum. But it is clear that the true picture of the origin of the meteorites is beginning to emerge.
The Holy of Holies in the Temple of Diana at Ephesus has been destroyed. But the Kaaba has been carefully preserved, although there seems never to have been a true scientific examination of it. There are some who believe it to be a dark, stony rather than metallic meteorite. Recently two geologists have suggested, on admittedly quite fragmentary evidence, that it is instead an agate. Some Muslim writers believe that the color of the Kaaba was originally white, not black, and that the present color is due to its repeated handling. The official view of the Keeper of the Black Stone is that it was placed in its present position by the patriarch Abraham and fell from a religious rather than an astronomical heaven—so that no conceivable physical test of the object could be a test of Islamic doctrine. It would nevertheless be of great interest to examine, with the full armory of modern laboratory techniques, a small fragment of the Kaaba. Its composition could be determined with precision. If it is a meteorite, its cosmic-ray-exposure age—the time spent from fragmentation to arrival on Earth—could be established. And it would be possible to test hypotheses of origin: such as, for example, the idea that some 5 million years ago, about the time of the origin of the horninids, the Kaaba was chipped off an asteroid named 22 Kalliope, orbited the Sun for ages of geological time, and then accidentally encountered the Arabian Peninsula 2,500 years ago.
* Unexpected discoveries are useful for calibrating pre-existing ideas. G. W. F. Hegel has had a very powerful imprint on professional philosophy of the nineteenth and early twentieth centuries and a profound influence on the future of the world because Karl Marx took him very seriously (although sympathetic critics have argued that Marx’s arguments would have been more compelling had he never heard of Hegel). In 1799 or 1800 Hegel confidently stated, using presumably the full armamentarium of philosophy available to him, that no new celestial objects could exist within the solar system. One year later, the asteroid Ceres was discovered. Hegel then seems to have returned to pursuits less amenable to disproof.
CHAPTER 16
THE GOLDEN AGE
OF PLANETARY
EXPLORATION
The unquiet republic of the maze
Of Planets, struggling fierce towards heaven’s free
wilderness.
PERCY BYSSHE SHELLEY,
Prometheus Unbound (1820)
MUCH OF HUMAN HISTORY can, I think, be described as a gradual and sometimes painful liberation from provincialism, the emerging awareness that there is more to the world than was generally believed by our ancestors. With awesome ethnocentrism, tribes all over the Earth called themselves “the people” or “all men,” relegating other groups of humans with comparable accomplishments to subhuman status. The high civilization of ancient Greece divided the human community into Hellenes and barbarians, the latter named after an uncharitable imitation of the languages of non-Greeks (“Bar Bar …”). That