[LEAPSECS] Straw men

Rob Seaman seaman at noao.edu
Mon Jan 9 09:00:42 EST 2012

Clive D.W. Feather wrote:

> we've moved from local mean solar time to GMT to summer time to double summer time to back again to BST to summer time again

And another straw man. Only proponents of redefining UTC have ever suggested this superficial view of a connection to apparent solar time. Many arguments on leapsecs start with some erroneous premise confusing periodic phenomena (static or seasonal offsets as a special case) with the secular error that redefining UTC would introduce.

> If paying the price of an additional one-hour shift in 12 generations time

> is the price to pay for getting rid of leap seconds, I'd happily pay it in

> a heartbeat.

Note the conditional. Yet another straw man.

That is certainly not the price for the astronomical and aerospace communities. One second of time is 15 seconds of arc (unless you are content only observing at the poles). Redefining UTC will break large numbers of telescopes, software and systems within a year or two. New worldwide infrastructure will have to be designed, deployed, maintained (and funded).

Nobody has looked to see what the larger impacts will be.

>> It all comes down to what time on the clock should tell us: earth angle (eg, where the sun is) or elapsed time since an epoch. This whole issue boils down to that.


> Indeed. But Rob *defines* time as earth angle and then tries to tell us

> we're breaking the whole world.

No. The real world defines time-of-day as Earth rotation angle. Atomic time is something else. They are not the same thing. They are both needed. The engineering requirements of civil timekeeping include time-of-day.

There are engineering implications if we try to pretend that the two different types of time are one-and-the-same. Those implications have not been sufficiently dealt with (in whatever fashion).

Rob Seaman
National Optical Astronomy Observatory

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