Impressing the Natives
In Mark Twain's A Yankee at the Court of King Arthur, the eponymous hero is saved from being burned alive by the chance recall that there is to be an eclipse of the sun that day, which he duly "foretells" as a threat. The superstitious king and court hasten to set him free in order, so they believe, to get the sun back again. Tintin, the boy reporter cum detective made famous by Herge, employs a similar stratagem to win freedom for himself and his companions when they are imprisoned by the Incas and about to be burned alive. If my recollection of a quick scan through the book is correct, the heroes of Rider Haggard's King Solomon's Mines also made use of an eclipse.
Such preying on the credulous has a longer history than these modern writers perhaps realise, for Plutarch, in his Moralia, tells of a certain Aganice, who inspired considerable awe through the exact same method.
Aganice, the daughter of Hegetor, a Thessalian lord, who understanding the reason of the eclipses of the moon, and knowing beforehand the time of her being obscured by the shadow of the earth, made the credulous women believe that it was she who at those times unhinged the moon and removed her from the sky.
Actually, it is quite interesting to read what Plutarch has to say about eclipses, for he clearly understood that the moon is eclipsed by the earth's shadow and in one of the essays that makes up the Moralia gives a quite modern-sounding explanation of how it all works. He is rather less convincing when he starts to display his knowledge of Platonic and Pythagorean philosophy. Do read the next couple of paragraphs, but don't even try to understand them, not unless you have a good supply of aspirin in the house for the inevitable headache!
For it was not out of vain-glory, to boast his skill in the mathematical sciences, that Plato inserted in a treatise of natural philosophy this discourse of harmonical and arithmetical medieties, but believing them both apt and convenient to demonstrate the structure and composition of the soul. For some there are who seek these proportions in the swift motions of the spheres of the planets; others rather in the distances, others in the magnitude of the stars; others, more accurate and nice in their enquiry, seek for the same proportions in the diameters of the epicycles; as if the Supreme Architect, for the sake of these, had adapted the soul, divided into seven parts, to the celestial bodies.
Many also there are, who hither transfer the inventions of the Pythagoreans, tripling the distances of bodies from the middle. This is done by placing the unit next the fire; three next the Antichthon, or earth which is opposite to our earth; nine next the Earth; 27 next the Moon; 81 next to Mercury; 243 upon Venus; and 729 upon the Sun. The last - 729 - is both a tetragonal and cubical number, whence it is, that they also call the sun a tetragon and a cube. By this way of tripling they also reduce the other stars to proportion.
But these people may be thought to dote and to wander very much from reason, if there be any use of geometrical demonstration, since by their mistakes we find that the most probable proofs proceed from thence; and although geometers do not always make out their positions exactly, yet they approach the nearest to truth when they say that the diameter of the sun, compared with the diameter of the earth, bears the proportion of 12 to 1; while the diameter of the earth to that of the moon carries a triple proportion. And for that which appears to be the least of the fixed stars, the diameter of it is no less than the third part of the diameter of the earth, and the whole globe of the earth to the whole globe of the moon is as twenty-seven to one. The diameters of Venus and the earth bear a duple, the globes or spheres of both an octave proportion. The width of the shadow which causes an eclipse holds a triple proportion to the diameter of the moon; and the deviation of the moon from the middle of the signs, either to the one or the other side, is a twelfth part. Her positions as to the sun, either in triangular or quadrangular distances, give her the form when she appears as in the first quarter and gibbous; but when she comes to be quite round, that is, when she has run through half the signs, she then makes (as it were) a kind of diapason harmony with six notes.
But in regard the motions of the sun are slowest when he arrives at the solstices, and swiftest when he comes to the equinoxes, by which he takes from the day or adds to the night, the proportion holds thus. For the first thirty days after the winter solstice, he adds to the day a sixth part of the length whereby the longest night exceeds the shortest; the next thirty days he adds a third part; to all the rest till the equinox he adds a half; and so by sextuple and triple distances he makes even the irregularity of time.
The trouble with Greek science was that the philosophers applied considerable mental prowess to constructing theories - some of which were remarkably accurate, though the most are pure gibberish - and had no concept at all of conducting experiments to see whether their theories were correct or not.
Which, I suppose, not only makes Thales' achievement in working out the reason for eclipses and using that knowledge to predict them so remarkable, but makes the Antikythera Mechanism so unusual.
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| One of the three surviving fragments of the Antikythera Mechanism. Note the scale engraved on the circle. |
Discovered in 1902 by sponge divers operating off the Greek island of that name, the broken and corroded lump of brass has intrigued scientists, historians and archaeologists ever since. It has been described variously as a clock, a navigational device and a mechanical astrologer, but a team led by Mike Edmunds of Cardiff University in Wales believes that it has finally cracked the mystery.
Edmunds used a CT scanner to peer through the rust and accretions that cloak the device and then based a reconstruction on the information he gained. "The real significance of this is just how sophisticated the device was - much more complex than a modern wristwatch," says Edmunds. "It is beautifully designed."
Certainly we have to stand in awe of the precisely cut gears and cogs which made up the Antikythera Mechanism, but in view of the fact that most researchers agree that only about a quarter of the complete device has survived, any modern study has to be tentative in its conclusions. Edmunds, however, has no such reservations. He believes that it was created to predict eclipses using only the positions of earth, sun and moon.
He may well be right - but for myself, I retain an open mind. A new study may reach a different conclusion or some more sponge diving might find the rest of the device - probably the only way to be sure exactly what the Mechanism was supposed to do.
© Kendall K. Down 2009
