Time Keeps Beating… To The Cycle Of An Atom
So you want an atomic clock? They are the most accurate
form of time keeping out there, and even have a space age
name. But what exactly are they, and how much should we
pay for one? While we are at it, are they actually worth
the money?
Atomic clocks are not really so different from any other
kind of clock. At the heart of a clock there needs to be
something that taps out a really regular rhythm. Then this
beat is turned mechanically or digitally into a time we can
understand. It doesn’t really matter how rapid the beat
is, as long as it is regular, but a pendulum clock is set
up to tick and tock every second. These old-fashioned
clocks are pretty accurate, as long as you remember to keep
them wound – a good grandfather clock can be accurate to
half a second a day.
Sources used for keeping time have expanded past the source
used for pendulum clock, which incidentally was first
planned by Galileo but never made by the man himself. One
example of a modern use of science in clock technology is
quartz, which is often used in today’s digital watches.
When a small electrical current touches quartz, the quartz
vibrates at a relatively reliable frequency. Several modern
clocks and watches take their cue from quartz and are able
to keep time at an accuracy of one-10th of a second each
day.
This is where a lot of people are happy to stop – hey, who
cannot afford to lose a tenth of a second over the 86,400
that we enjoy each day? For most of us it simply isn’t an
issue, but there are some applications where accuracy is
more important (science and navigation for example), which
is why the atomic clock was developed. The atomic clock is
very, very accurate.
The atomic clock is so accurate that the one in the National
Institute for Standard and Technology office is off only
30-billionth of a second every year! If you work for this
office, you have no excuse for being late. The atomic clock
operates through a rhythmic source called cesium that is
extremely predictable and precise. The element cesium has a
fast but always constant resonant frequency. For those who
are interested, the official definition of a second, as
established in 1967, is “9 billion, 192 million, 631
thousand 7 hundred and 70 cycles of a cesium atom…”
While the NIST atomic clock is a great example of a high-end
model, other versions of atomic clocks exist. It’s somewhat
unlikely that the average person would own one since the
hand-held versions cost upward of $20,000. You may be
asking by now what are those $20 versions you’ve seen
advertised? These “atomic” clocks and watches aren’t really
atomic. These clocks and watches make contact with a real
atomic clock, read its time by way of radio, and update its
time based on that source. This chain of events gives you
the advantage of maintaining time through the accuracy of an
atomic clock but at a fraction of the price. For most of
us, this convenience is mostly academic rather than a
necessity since we really don’t need to keep time to this
degree. Still, there is one advantage to having one of
these clocks – you’ll never have to fiddle with setting one!
That’s why so many people buy these clocks and find their
price so worthwhile.
