Thursday, October 22, 2009

Decoding the Heavens

Vision is the art of seeing what is invisible to others.
-Jonathan Swift

The heavens themselves, the planets, and this centre,
Observe degree, priority, and place,
Insisture, course, proportion, season, form,
Office, and custom, in all line of order.
-William Shakespeare

Left to my own powers of observation, I could not tell you much about the movement of the sun and moon and planets across the sky. On the other hand, I’m always impressed that the people of olden times recognized the regular patterns of celestial events.

This astronomical knowledge was manifest in the arrangement of monoliths, the alignment of earthworks and the observance of seasonal rituals. Add to this list the Antikythera mechanism, termed “the most important single item to come from ancient Greece” and “one of the greatest mechanical inventions of all time.”

In her new book Decoding the Heavens Jo Marchant writes about the discovery of the Antikythera mechanism and the century-long effort to decipher its purpose.

In the year 1900, Mediterranean sponge divers found a Greek shipwreck from 70 BC. One of the items they retrieved was a corroded mass of metal parts. Archaeologists eventually reconstructed the sophisticated assemblage of dials, pointers and more than thirty interlocking gears.

It was unlike anything else ever identified from that era. Researchers speculated it was a clock, or a calculator, or a navigational tool similar to an astrolabe. The complexity of the instrument was unrivalled until the development of astronomical clocks in Medieval Europe 1400 years later.

The Antikythera mechanism was so uncharacteristic of its time that Erich von Daniken, in Chariots of the Gods, contended that it must have been introduced by interplanetary aliens. Somehow, more than 2000 years ago, the Greeks possessed a machine that tracked the movement of heavenly bodies. Marchant explains:

Whoever turned the handle on the side of its wooden case became master of the cosmos, winding forward or backwards to see everything about the sky at any chosen moment. Pointers on the front showed the changing positions of the Sun, Moon and planets in the zodiac, the date, as well as the phase of the Moon, while spiral dials on the back showed the month and years according to a combined lunar-solar calendar, and the timing of eclipses.

Inscribed text around the front dial revealed which star constellations were rising and setting at each moment, while the writing on the back gave details of the characteristics and location of the predicted eclipses. The mechanism’s owner could zoom in on any nearby day – today, tomorrow, last Tuesday – or he could travel far across distant centuries.

For the first time in history it was possible to revisit the past and to predict the future. It was possible to control time itself.

It took decades of intensive study to finally crack the code of this miraculous device. Now we know what it is and how it works. Mysteries remain over who managed to create such a thing. Marchant expresses her wonder and admiration for whoever it might have been:

My lasting impression is not of the similarities between our world and theirs, but the differences. We now understand more about the universe than any previous civilisation could have dreamed. We observe and measure the objects in our solar system by the nanosecond and send spacecraft to visit them. We have photographed the Earth from space, sent men to the Moon and beamed pictures back from Mars. We have caught stardust from the tail of a comet and probed the atmospheres of planets circling distance suns. We understand better than ever the true extent of our universe, how it began and how it will end, and the nature of our place within it.

Have we also lost something? At the very least, we’re missing out on the best light show on the planet. Living in today’s permanently illuminated towns and cities, most of us have little sense of the rhythms of the sky; the intricate dance of the Earth, Moon and Sun, the wandering of the planets or the circles of the stars. Finding out who made the Antikythera mechanism and why also turns upside down any notion we might have had about ancient technology being “primitive” and our own being so “advanced”. After all, where we see practical machinery that can measure time accurately and do work, the Greeks saw a way to gain knowledge, demonstrate the beauty of the heavens and get closer to the gods.

Decoding the Heavens, A 2000 Year Old Computer and the Century-Long Search to Discover Its Secrets, by Jo Marchant, De Capo Press, 2009.

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