[LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1

Rob Seaman seaman at noao.edu
Fri Sep 3 04:34:10 EDT 2010

On Sep 3, 2010, at 1:04 AM, Ian Batten wrote:

> I have a clock ticking SI seconds at arbitrarily high precision and resolution.

Examine your premises. At some point in the past five years or so there was a thread discussing the distinction between clocks and timers. I won't attempt to recover the subtleties of that thread at this time of night. (Though I suppose the ITU would assert that my biorhythms are immaterial :-)

> How do I find out how many SI seconds I should count in order to count ten UT1 seconds? Can I determine that value prospectively, or only retrospectively?

Suppose a timer to be a standalone source of ticking SI seconds. A "clock" implies subjugating that timer to an external discipline such as mediated by NTP, for example. Supplying a discipline from an ensemble of officially blessed atomic clocks is no better than applying a discipline from the wobbling Earth. (The clocks may be more stable, but they are guaranteed to be shorter lived if nothing else :-) In particular, constructing an ensemble timescale is as retrospective a task as measuring the meridian transit of fiducial stars in support of calculating UT1.

Here's an interesting preprint (http://arxiv.org/abs/1008.4686) with pertinence to the feasibility of fitting a model to data of putatively "arbitrarily high precision and resolution".


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