World Enough and Time

September 23, 2008

"But at my back I always hear
Time's wing'd chariot drawing near..."
-- Andrew Marvell, "To His Coy Mistress"

As if we needed more reminders that time is fleeting for us mere mortals, last week Corpus Christi College at the University of Cambridge in England unveiled a $1.8 million mechanical clock designed by industrialist-turned-inventor/horologist John Taylor (an alumnus of the college). Introduced by cosmologist Stephen Hawking, of all people, the Corpus Clock is quite the conversation piece. Seven years in the making, the college intended the timepiece to be "both a radical new way of telling time, and a hard-to-miss piece of public art with an existential message." (Some might find that message to be more in the nihilistic vein.)

Lots of things make it unique. For starters, it has no hour, minute, or second hands, or even the standard digital numerical display of the current time. Rather, it tells time via three pairs of concentric stacked annular disks. Slits have been cut into the clock's gold-plated face, and as the wheels turn, this enables light to selectively escape from a set of light-emitting diodes (LEDs); the light display pauses at the correct hour, minute and second.

But that's not all! Time seems to pause occasionally, to run unevenly, and even run backwards now and then -- built-in mechanical tricks to mess with the viewer's mind, although it is designed to return to the correct time every five minutes. Oh, and the Corpus Clock strikes the hour with the sound of a chain dropping into a wooden coffin. Sheesh, why not just have the Grim Reaper perched on top, with its characteristic long black hooded robes and scythe?

Instead, the unique timepiece is crowned by a massive mechanical grasshopper, dubbed the Chronophage ("time eater"), that opens and closes it jaws over and over, symbolizing the devouring of time. In fact, it is the Chronophage that serves as the release mechanism enabling the clock's gears to move forward in fixed intervals.

The inclusion of the (slightly creepy) grasshopper is an inside joke of sorts. Taylor says he designed the clock in part to remind himself of his own mortality, but also in homage to 18th century British clockmaker John Harrison, immortalized several years ago in Dava Sobel's bestselling book, Longitude for his invention of marine chronometers for determining longitude at sea. Harrison also invented something called a "grasshopper escapement" in 1722: a novel, low-friction mechanism to drive a clock's gears forward by a fixed amount with each swing of a pendulum. (This was in the days of pendulum clocks.)

You can find a useful animation of the grasshopper escapement here. The biggest advantages gained from Harrison's invention were the regularity of operation, and the fact that the mechanisms didn't require lubrication. The latter is especially key, since in Harrison's time, the only available lubricants were messy and didn't last very long. Clocks had to be stopped and cleaned all the time, making it difficult to assess long-term performance of various timekeeping devices -- particularly the effects of temperature. Mostly, though, the grasshopper escapement was a unique curiosity; it wasn't widely used in timekeeping devices. Taylor, for one, obviously feels it deserves to be more widely known.

Photo: Corpus Christi College/University of Cambridge

Comments

[DAd]

oops

link is wrong

[DAd]

in the first link, i mean

found it:

an "a" was missing