[LEAPSECS] 1.26 microseconds

Rob Seaman seaman at noao.edu
Mon Jun 13 17:43:49 EDT 2011

On Jun 13, 2011, at 2:18 PM, Poul-Henning Kamp wrote:

> In message <96366060-430F-451B-81CC-D63082CD971F at noao.edu>, Rob Seaman writes:


>> So "day" is a word referring to Earth Rotation?


> As a first order approximation, the same way a year is a first order

> approximation to earth orbital position.

Does "first order approximation" mean stationary over long periods of time?

Note, of course, that no such language is in the ITU draft.

> Poul-Henning


> PS: I read an interesting note recently about how the fact that

> years have varying lengths have become an issue for determining the

> "official" half-life of long lived radioactive isotopes: Many

> geological methods just counted years, but hadn't considered how

> long those years were.

Reference? Length-of-day varies in the rich and wonderful ways we've discussed, lo these many years. If variation of length-of-year is a significant issue it has not been stated previously in this context.


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