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.



Copyright 2005 Reg Atley. All rights reserved.

Reg Atley developed atomicclocku.com - to make it easy to find atomic clocks and anything to do with them. Reg publishes a periodic newsletter on Atomic Clocks. For details, go to http://www.atomicclocku.com/articles/optin/optin.html

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