[LEAPSECS] A consolidated approach.

Rob Seaman seaman at noao.edu
Wed Dec 15 10:49:13 EST 2010

On Dec 15, 2010, at 7:49 AM, Tom Van Baak wrote:

> As for your "universal" comment; that's problematic. I suspect

> you will find many uses of that word which are quite unrelated

> to astronomy; from universal studios to universal health case.

Lots of terminology is overloaded. The ITU on the other hand is attempting to "underload" the historical meaning of "Universal Time" as an analogue to "Greenwich Mean Time". It is the long and tangled history that matters, not the wordplay. Many communities - not just shabby and shameless smelly old astronomers - refer to "UT" as being equivalent to "GMT". The ITU is acting as if it won't be ridiculously confusing (and yes - potentially dangerously so) for "UTC" to mean nothing whatsoever similar to "UT" - and for the historical sequenced of UTC to have a kink in the middle with differing rates on either side.

> If in fact a revised or new time scale still has the word universal

> it in, chalk it up to history. I mean, we still talk about dialing a

> number, even though rotary phones are long gone. We use the

> word "on line" even though there is now rarely a telephone wire

> involved (and don't you love, "wireless on-line").

The ITU is actually suggesting the opposite - that they serve as dictionary police to dissuade such colloquial usage. They don't want to "chalk it up to history", they want to erase the blackboard.

"Tap-tap-tap...excuse me Ma'am, did I just overhear you say that you were going to 'dial your cellphone'? Rather, surely you meant to say that you were going to 'use the keypad to enter a phone number'? This is a serious offense! You will have to come with me down to the station."


> Couldn't one could equally make a case that basing a time scale on a generic undisturbed cesium atom is far more "universal" than the unpredictable rotation of a particular planet?

No. And why is "predictability" the defining characteristic of a useful timescale, rather than the actual macroscopic phenomena (time-of-day) that is being predicted?

These are two different kinds of time - interval time and earth orientation time. "Universal" is a term that has historically denoted the latter. It is puerile to arbitrarily shift it to the former.

If wordplay really seems that important, note that they (that shadowy "they") are seeking to replace "International Atomic Time", a nicely descriptive phrase, with "Coordinated Universal Time" - a name that is even less appropriate for what has heretofore been rather shakily called "atomic".

Pick a different name. This was the consensus in Torino in 2003.

> In which case you should move to strip the word universal from UT1, etc.

As neat an example of reductio ad absurdum as there is.

> A suggestion -- call your the new time scale ISO-86400. If it includes leap seconds, then go for ISO-235960.

I support the implicit recognition here that there are (not "needs to be", not "should be", but "are") more than one timescale. An appropriate political question (with stakeholders far beyond ITU, ISO or BIPM) is whether civil timekeeping should remain tied to one of the subset of these timescales that expresses mean solar time.

It is also an interesting notion to explicitly separate the technical name of the timescale from the human-usable name. This is just the notion of an indirect pointer from computer science (or reflects activities like drug marketing, "Tylenol" = "acetaminophen", for instance).


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