Re: [LEAPSECS] Internet-Draft on UTC-SLS

From: M. Warner Losh <imp_at_BSDIMP.COM>
Date: Thu, 19 Jan 2006 14:22:39 -0700 (MST)

In message: <E1EzgPT-00022K-00_at_alva.home>
            Tim Shepard <shep_at_ALUM.MIT.EDU> writes:
: > The serious timekeeping people gave up on rubberseconds in 1972 and
: > I will object with all that I can muster against reinventing them
: > to paste over a problem that has a multitude of correct solutions.
:
: As I learned from a recent posting to this mailing list, it seems that
: even TAI has rubber seconds (adjustments to the rate is made from time
: to time to compensate for errors that have been accumulating, making
: TAI a better (more useful) approximation time).
:
: Do you object to those adjustments (rubber seconds) to TAI as well?

TAI changed the definition of the second in 1977 by one part in 10^12.
Those weren't rubber seconds. It again slowly changed the definition
over 3 years of the second by 2 parts in 10^14 ending in 1998. They
were made not to correct the phase of TAI, but rather to correct the
length of the second to more closely match the SI second definition.
No phase adjustments were made to TAI.

Rubber seconds, on the other hand, are a steering device designed to
keep time in sync with another clock, in this case the earth. They
aren't changing the definition of the second, but rather are inserting
phase adjustments to the timescale. The goofy scheme that existed
prior to 1972 fell into this latter category.

Warner
Received on Thu Jan 19 2006 - 13:25:51 PST