Today, we look for the first clocks. 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.
When was the mechanical
clock invented? It's a hard question -- not because
people wrote too little about early clocks, but
because they wrote the wrong things. The problem is
that the mechanical clock seemed at first to be a
mere improvement on the older water clock, which
had been around for well over a thousand years. The
existing records ignore working details, so it's
hard to tell when the changeover took place.
The water clock used a steady regulated flow of
water into a vertical tank. The rising water level
in the tank indicated the time of day. That all
sounds simple enough, but water clocks were large
ornate structures with a lot of supporting gear
work and general fancification. Like the later
mechanical clocks, they often tolled the hours on
bells, for example.
Mechanical clocks differed by using an escapement
mechanism to regulate time. The balance wheel on a
watch or the pendulum on a grandfather's clock is
an escapement -- a mechanism that ticks in a steady
rhythm and lets the gears move forward at a steady
rate in little equal jumps.
The first escapement we know about was described in
AD 1250 by the French engineer Villard de
Honnecourt; but it wasn't used to control a clock.
Instead, it was used in a cute little gadget that
steadily pointed at the sun while it moved through
the daytime sky.
Monastery records after 1250, for the next hundred
years, refer to clock bells, to gearing, to clock
towers. But clock terminology rode right through
the changeover. The first clear drawing of a
mechanical clock was given us by Jacopo di Dondi
and his son in 1364, and they'd probably been
building them for at least 20 years by then. We
can't be sure, but the first mechanical clock was
probably made in the late 1200s.
It's strange that such an earth-shattering change
could be that invisible. Water clock inaccuracies
had bottomed out at around 15 minutes a day, and
that's about as well as the first mechanical clocks
did. But now, suddenly, engineers began to cut that
error in half every 30 years, right up into the
20th century. It wasn't long before mechanical
clocks swept the imagination of the Western world
and led to new standards of precision -- first in
instruments and ultimately in thought itself.
The most important technology of an age might not
be the most obvious one. Great changes sometimes
come in on little cat feet. And that's what the
mechanical clock did in the thirteenth century.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
