A Perfect Watch is always Fast

Let's say that you bought a perfect watch on January 1, 1972. By perfect, we mean that each and every second measured by this hypothetical watch is exactly equal to a SI second - defined in 1967 as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". Let's say also that, comforted by this extreme accuracy, you've never adjusted the watch or had to change to battery or wind it up or whatever. After all it is a perfect watch, right?

Sorry to tell you that your watch is now 24 seconds fast. Yep. You see, measuring the passage of time is not quite the same as telling the time. Time itself is but a concept, a human observation of change if you will. On the other hand, "the time" [of day] is our expression of an agreed instant in the passage of time. In fact, the time of day, or the definition thereof, has been messed around with ever since the first non-sundial clock was invented.

You would think that the invention of atomic clocks would clear everything up. After all, atomic clocks are almost as good as the perfect watch that you bought back in 1972. Unfortunately, we still have the same problem in modern times that the ancients had. Days are still varying in length - not just the period of daylight versus night, but also the actual length of each day varies during the year. Not to mention that the wobble of our planet (about once every 26,000 years) causes a change in the length of each year and that the planet itself is slowing down due to tidal friction.

Before the second was re-defined in 1967, it was defined with respect to the mean solar day and thus measured the passage of ephemeris time. However, the first atomics clocks proved that even ephemeris time was not perfectly constant so, up until 1967, they were actually adjusted to keep ephemeris time, known quaintly as "ET".

These days we still match "the time" to our planetary motion but now it is done by adding leap-seconds when required by our slowing planet. It is only by adjusting atomic time with leap-seconds do we arrive at the familiar UTC which is now truly "the time", as far as everyone on the planet is concerned. In 1972, when UTC was invented, it was already slow to the atomic clock by 10 seconds and since then 24 leap-seconds have been added - which is why your perfect watch is now 24 seconds fast!

Best regards, xpatUSA

Time Zone Tyranny - fight back!

In the past, humans arose with the Sun, went to work (with perhaps a break for lunch at noon) and quit their labors at Sundown. All very natural.

Then came clocks with equal hours followed by minutes and finally seconds. Now we have to have the most accurate watch possible in order to keep in sync with what could be called "civil time" complete with timezones and the changing of the clocks twice a year.

Spare a moment of pity for those unfortunates who live in Van Horn, West Texas, a city at almost 105 degrees West, but on Central Time. They're already an hour "fast" in winter but in early March they change to Daylight Savings time plus the Equation of Time causes their time-pieces to be about a quarter of an hour even faster with reference to the Sun. All this means that, at high noon in Van Horn, their time-pieces say 2:15 pm!!

Now if you're retired or currently "resting" you can fight back and lead a more natural life. Here's how:

Go and buy a watch with a rotating 12-hour bezel. (Hey, we always need another watch - this time for health reasons ;-). Spend some time Googling to find out how far off civil time is at your home. Then, for those in the West: turn the bezel back by that many hours; Eastern folks would turn it forward. Then set the watch to local solar time. If you've got it right, the sun should be overhead at 12 o/c. If you ever have cause to know civil time, just look where the hour hand points to on the bezel (ignore the minute hand).

I'm trying it out on this P650 . .



Katy, Texas is at almost 96 degs West. With our wobbly planet in it's elliptical orbit, the sun is overhead at 13:23 civil time this week, ie an hour and 23 minutes fast. The pic was taken at about 9:30 pm CDT and the local solar time is 8.08 pm.

Best regards,

xpatUSA