[LEAPSECS] "China move could call time on GMT"

[Rob Seaman]

Hi Tom,


>> Earth orientation clocks and even-interval chronometers are simply two different kinds of timekeepers.

> 

> Hi Rob,

> 

> That can be said for all clocks.  Any object with periodic motion can

> be made into a clock. Yes, some are bigger than others, some keep

> better time than others, but no two are ever exactly the same. What

> do you mean by "two different kinds of timekeepers"? Are there many

> different "kinds" or just two?


This has been a talking point on the list before.  Steve Allen in particular has clarified the distinction between clocks and chronometers.

The phrase "keep better time" illustrates the issue.  Better relative to what definition?  Building "better" atomic timepieces is an exercise in precision.  Building "better" time-of-day clocks is an exercise in accuracy to an external waveform.  TAI is a metronome.  UTC is a protractor.

As you say, there could be additional parameters of interest.  The ITU is proceeding with a naive (and expensive) agenda that cadence is the same thing as angle.


> The word "even-interval" has not appeared on the list before. What

> do you really mean by that? On a large scale, Earth rotation itself is

> an even-interval chronometer, isn't it?


The list has tried numerous vocabulary terms on for size.  TAI aims for a constant precise cadence (frequency).  How would you describe that concept as opposed to Earth orientation (angle)?

Consider an alternate point of view.  Rather than an SI unit of duration called the "SI-second", how about reifying the equivalent standard unit in frequency space, the Hertz?  Then the original meaning of the word second as an angle would remain?

Rob