[LEAPSECS] Skepticism

[Rob Seaman]

On Dec 30, 2010, at 5:06 PM, Jonathan E. Hardis wrote:


> In the large, it is amazing to me that the "countable few" on this mailing list still don't get it.  One would think that at least you guys would acknowledge that when the many experts that have been involved with ITU-R Study Group 7 reached their conclusion it wasn't done hastily, foolishly, or in isolation.


Oh, puhlease.

There are lots of "experts" contributing to this list - experts in lots of areas of which the ITU is completely oblivious.

It is *hasty* to force a decision when the current definition of UTC is viable for centuries.  It is *foolish* to act before securing consensus.  Isolated?!?  Of course they are isolated!  Point to one post a representative of "ITU-R Study Group 7" has made to this list.


> To repeat myself, the punch line is this:  NO ONE is advocating a perpetual drift apart between atomic time and "universal" time (sundial time).


Whatever they are advocating (which appears to include the deprecation of TAI), the proposal includes nothing about the inevitable future release of the embargoed leap seconds (or equivalent).  It includes nothing about what will replace the DUT1 mechanism - suddenly to increase from negligible importance to large and growing importance.  If they are not advocating a perpetual drift, the proposal should address this.

On its face the proposal assumes zero implications from ceasing leap seconds.  This is certainly not true for the astronomical community.

You refer to universal time as "sundial time", presumably meaning solar time.  Thanks for this recognition!  That said, universal time is "mean" solar time (sidereal time adjusted by one day per year for lapping the sun), not "apparent" solar time as indicated by sundials.  Mean solar time counts the length of the natural synodic day on planet Earth, that is, civil time.


> LATER one can have ANOTHER discussion about perhaps adopting leap-second schemes with regular and predictable insertions (like we do with days in leap years), or "leap minutes," or ... whatever.


The actual proposal on the table sucks.  As someone else points out, it is quite possible to break international civil timekeeping to the point that all the King's men can't put it back together again.  We should act prudently and with due diligence.  There is no hurry.  There are options that have not been entertained by the monomaniacal ITU process.

Leap seconds are a means to an end.  Civil timekeeping is based on mean solar time.  The ITU can cheat for some purposes for some "users" for some length of time.  The details of the proposed kludge matter.  Those details should be worked out in advance.

Rob Seaman
National Optical Astronomy Observatory