Today, let's 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.
We've said a lot about
mechanical clocks in this series. Well, the time
has come to consider the clock's antithesis, the
hourglass. First, how old do you suppose the
hourglass is: two thousand years? Four thousand
years? Engineer/historian Robert Balmer goes
looking for the answer. He finds no evidence of the
hourglass until the early 1300s. Oddly enough, it
came into use at almost exactly the same time as
the first mechanical clocks. The hourglass is only
about seven hundred years old.
Of course the hourglass is kin to the water clock.
Both depend on a medium flowing out through a hole.
But the hourglass has its own technological
personality. On the positive side, it's far
simpler and cheaper than the mechanical clock or
the earlier water clock. Resetting it after it runs
down couldn't be simpler. It doesn't vanish the way
a graduated candle does. Its accuracy isn't bad
once you solve some problems. You can't load just
any old sand into it. You have to find a
free-flowing material that doesn't absorb water on
a humid day and clog up.
On the downside, an hourglass is a short-term
timepiece. The very name says it's hard to make one
that runs more than an hour. The other big drawback
is that it 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 shows 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 shipboard. They
ran neither long enough nor accurately enough to be
of much use in marine navigation. They were a poor
person'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 for
the wheel of fortune. But the hourglass, whose
sands run out, was a thing of this base earth. It
became a metaphor for the running-out-of-sands 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, the hourglass
segmenting it -- the clock speaking of
timelessness, the hourglass showing us finality --
the clock evoking things celestial, the hourglass
reminding us of base earth. They are Yin and
Yang.
Why was the hourglass so late in coming? Maybe it
had to wait for its opposite, the mechanical clock,
to be invented. The clock and the hourglass create
technological parity. Either, without the other,
would provide an unbalanced metaphor, and that
subtle fact can be far more important than it might
seem.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
