Accuracy has been the goal of the clockmaking game since the beginning. Back when water clocks were all the rage, for example, their chief drawback wasn't that incessant drip, drip, drip, but their incessant "leakage" of time.
Timekeeping got a big boost with the invention of the pendulum clock in the 17th century, and again in 1928, with the invention of the quartz clock. Similar vibrating quartz crystals drive the mechanism found in almost every wristwatch today. Although quartz clocks can stay accurate for weeks, or even months at a time, scientists are no longer impressed by this. These days, they use the principles of quantum mechanics to keep clocks close to the money in devices called atomic clocks. Like most clocks, an atomic clock creates periodic movements (oscillations or cycles) and then counts them.
In the old pendulum clocks, a weight oscillated at a fairly constant frequency, so the clockmaker simply had to invent a mechanism to count the swings and drive the clock's hands. But in an atomic clock, the oscillations occur in an electromagnetic field that causes transitions between two quantum-mechanical conditions of atoms. In the commonly used cesium 133 atoms, these occur at about 9.19 billion times per second (9,192,631,770 to be exact). This transition frequency is so dependable that, if external conditions are right, the atoms will keep on "ticking" at the same old rate. They may be boring creatures of habit, but they are ideal for keeping time.
After most sources of error are eliminated, atomic clocks get frighteningly accurate. For example, one cesium clock at the National Institute of Standards and Technology (NIST), is accurate to five parts in 1015. This staggering precision works out to an error of about a billionth of a second per day. To put it another way, this clock will stay within one second of true time for six million years.
Those of us who mutter "Just a second" to mean "In 5 or 10 minutes" may not understand the need for clocks accurate to one second in six million years. So what's the big lure of hyper-accurate time?
Global positioning satellites need accurate time. The Air Force-operated GPS system can determine – to several feet in accuracy – the three-dimensional position of a receiver anywhere on or off the Earth. The receiver performs this trick by timing the arrival of signals from four or more GPS satellites, then doing a quick calculation to triangulate its position. Stephen Dick, the United States Naval Observatory's historian, points out that each nanosecond (or one billionth of a second) of error translates into a GPS error of one foot.
In other words, without accurate timing, GPS would stand for "Generally Puky System." Thus each of the twenty-four GPS satellites contains four atomic clocks, which get an accurate time transfusion daily from the Air Force, which "borrows" the time from the United States Naval Observatory.
So ... I bet you didn't know that knowing what time it is makes the whole sport of Geocaching possible, did you? Without precise time measurement, the Global Positioning System wouldn't (couldn't) exist. No GPS. No Geocaching. But were you paying attention or were you just skimming to find the cache? Better read it carefully or you won't find the cache. Yep. That's right. There's a quiz to see what you've learned.
A = The number of atomic clocks on each GPS satellite.
B = The error (in feet) introduced by 1/1,000,000,000 second error.
C = Cesium # atoms?
D = The pendulum clock was invented in what century?
E = How many million years before a one second error is introduced?
So do you have an appreciation for how important it is to know what time it is? Are you ready to find the cache? (Of course you are!) Here it is.
To find the correct Latitude of the cache, multiply A by D. Add C. Subtract 8. Divide by 1000. Add the result to the minutes posted above for Latitide.
To find the correct Longitude of the cache, multiply D by E. Add A and B. Divide by 1000. Subtract the result from the minutes posted above for Longitude.
The cache is about 6 steps off the trail but no bushwacking is required.
To check your answers and/or to verify your final coordinates use my Puzzle Cache Verifier.
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If you are a Geocacher in the state of Washington, please join the Washington State Geocaching Association. This is a great way to get the most out of Geocaching in our region. Simply go to geocachingwa.org for details!
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