Marie-Antoinette's Watch: Adultery, Larceny & Perpetual Motion

Chapter 5

Around the end of May the streets of Manhattan come to a standstill. Bike messengers halt on their rounds and the scions of Midtown come out for a smoke break and look, in amazement, at something called Manhattanhendge. It is on this day that New Yorkers, over-scheduled and anxious as they are, have something in common with ancient druids.

On the day of Manhattanhedge, the sun lines up perfectly with the offset grid of east-west streets. The sun, brilliant between the dark caverns of the buildings, sets over New Jersey like a comet coming to rest. Modern minds marvel for a moment and then forget about this once-a-year happenstance but, in prehistoric times, tricks like Manhattanhendge were, in short, the way humans told time.

Timekeeping was always at the forefront of human endeavor. It gave form to our days and helped us traverse great distances. It called the farmers to their fields and the priests to the vespers. It was - and is - the defining trait of humanity. After all, Robert Burns's dear mousie knew not the time when the farmer's scythe cut through his grassy home.

In about 5,000 BC, Celtic tribes built a tomb at Knowth, on the east coast of Ireland, whose position allowed it to act as a calendar and clock. A small beam of light crawled across the cave floor and carvings indicated various solar phenomena including the solstices. Such tombs - used for both astronomy and burial - played an important part in the daily lives of early humans, allowing them to measure times to harvest and to estimate the Metonic Cycle or the cycle of lunar and solar eclipses. A similar trick played an important part in Indiana Jones and the Raiders of the Lost Ark, proving that the play of light in darkness is a compelling meme even in modernity.

Because the ancients had little but sunlight and perhaps the imperceptible motion of a distant planet or star to tell the time (after all, astrology is nothing but time-telling mixed with a bit of hocus pocus), they had a much more fluid view of its passing. The day began when the sun rose and ended when the sun set. The end of twilight left a deserted and dangerous world with no real promise that the day would begin anew, and it was faith in the rising and falling of the sun that constituted early religions.

It is hard to say when "time," or the separation of the day into sections, became a measurable thing. According to one fairly visceral legend, the "division of the day into hours was first suggested by the regular exercise of the bodily functions of a consecrated monkey, called the Cynocephalus."28 More likely, however, watching the sun crawl across the ground in front of a tower was man's first inkling that his days were meted out in tick-tock bursts. Egyptian obelisks, in fact, doubled as sundials and the Book of Isaiah records the use of a sundial in 700 BC.

The earliest time-telling probably came from the notation of the period between sunrise and sunset, which, at first, consisted of four sections - four primitive hora or "parts of the day" - that slowly metamorphosed into the twentyfour-hour clock we now use. The Babylonians arguably created the first sixty-minute division of time and this was adopted by early Jews. The system used twelve hours of daylight and twelve hours of nighttime, with each hour divided into sixty minutes (sixty being a powerful number in Babylonian culture because of its easy divisibility).

Roman horologists also divided the day into twelve hours from sunrise to sunset, although the hours changed lengths depending on the season. They chose twelve in correspondence to the number of months - or lunar cycles - in the year.