[time-nuts] Why not TAI? (was: The future of UTC)

[Attila Kinali]

On Thu, 11 Aug 2011 09:20:04 -0700
"Tom Van Baak" <tvb at LeapSecond.com> wrote:

> What is missed in many discussions about time scales is intent
> or implied accuracy. If I manually adjust my Pacific Daylight
> Time wrist-watch ahead by 7 hours does it then become a UTC
> watch? If I further adjust it by 0.3 seconds can I now claim it's
> showing UT1? Can I even wear a wrist-watch that displays TAI?
> Is it possible for any clock with analog hands to display UTC?

This is IMHO an orthogonal issue to choosing the "right" time scale.
Yes, if a time scale is defined by using another time scale, then
accurate tracking and its uncertainty becomes an issue that needs to 
be properly defined. But same goes to any measurment equipment where
(absolute) time is meausred. If i capture events that occur randomly
and i want to timestamp them, i have to somehow get a time source that
fullfills my requiremtns of accuracy and precision.

For the most common events that occur at "random" times (like "lunch
with Bill") a time scale called "wrist watch" is good enough. Whether
it is defined using TAI, UTC or anything else is of secondary importance,
as long as it within a small confidence interval with regard to another
time scale called "Bill's wrist watch"

Same goes for any time scale used by scientific or technical installations
where we measure events or time. Yes, we define the time scale relative
to an existing one (most probably trackable to TAI), but it is not so
important whether it fullfills the accuracy requirements of the application.

> What we call a time scale is more than just an integer offset. I'm
> working on a paper that explores all these issues.

I'd like to read that. I hope you'll announce it on this mailinglist when
you are finished?

			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin