Today, let's take a look at the hourglass. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
How old is the hourglass?
2000 years? 4000 years? Oddly enough, historian
R.T. Balmer dates it at about the same time as the
first mechanical clocks. It's only about 700 years
old.
The hourglass had some strong characteristics. On
the positive side, it was far simpler and cheaper
than the mechanical clock or the earlier water
clock. Resetting it after it ran down couldn't be
simpler. And it didn't vanish when you used it, the
way a graduated candle did. It's accuracy wasn't
bad either, once some problems had been solved. You
couldn't load just any old sand into it. You had to
find a free-flowing material that was unresponsive
to humidity.
On the downside, hourglasses were pretty short-term
timepieces. The very name tells you it's hard to
find one that'll run more than an hour. The other
big drawback is that they can't be calibrated. Sand
moves downward in jerks. The edge of the sand is
uneven. If you mark five-minute intervals on the
glass, the sand will hit those marks differently
each time you turn it. An hourglass really tells
you only when an hour is up.
Hourglasses found their place in setting off blocks
of time. The time between canonical hours in a
monastery, or between watches on board ship. Of
course, they didn't run long enough or accurately
enough for marine navigation. They were a poor
man's timepiece -- a kind of clock for everyman.
Both the mechanical clock and the hourglass found
powerful symbolic roles during the Renaissance. The
complex mechanical clock with its rotary gears
became a metaphor for the heavenly spheres or the
wheel of fortune. But the hourglass, whose sands
run out, became a metaphor for that
running-out-of-the-sands that we all inevitably
face. It became, and it remains, a universal symbol
of death.
Two technologies, one simple, one complex, running
side by side -- the clock making a continuum of
time, and the hourglass segmenting it -- the clock
speaking of timelessness, and the hourglass showing
us finality -- the clock evoking things celestial,
and the hourglass reminding us of base earth.
Two technologies, Yin and Yang. Why was the
hourglass so late in coming? Maybe it had to wait
for its opposite, the clock, to be invented.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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