Wednesday, July 06, 2011

We've all got time enough to cry.

David Finkleman and his colleagues have published an article, "The Future of Time: UTC and the Leap Second", in the July-August 2011 issue of American Scientist (Vol. 99, No. 4, pp. 312-319; also: here and here) on the proposal by the Radiocommunications Sector of the International Telecommunications Union (ITU-R) to cease adding leap seconds to Coordinated Universal Time (UTC) so that it would no longer be kept in sync with the earth's rotation. The ITU-R organization is proposing this because it's just too hard.

GPS time already forgoes the use of leap seconds, and as a result, just in the time that GPS time has existed, the wall clock time we know from the rotation of the Earth, slowing due to the drag caused by the lunar tides, has drifted fifteen seconds from the time GPS keeps through the use of its atomic clocks. Hardware and software that displays wall clock time, but which synchronizes to GPS time, has to keep track of those missing leap seconds and add them back in. If such a change were to be made, it would mean UTC would be completely abstracted away from the wall clock time we use on a day to day basis.

Is this a good thing, or a bad thing? I don't know. But it sure as heck is not a minor thing. I got into the study of time for two reasons: it turned out to be critical to many of the products I've worked on in the past two decades, and much of the software I've used gets it wrong. UTC diverging from the wall clock time we use to manage our systems will only make this harder.

I've added an update to my 2006 article on date and time keeping "Does anybody really know what time it is?".


Steve Allen said...

How about some pictures to go with the references, or maybe a ticking illustration of the problem.

Chip Overclock said...

For those of you who just joined us, Mr. Allen is one of the co-authors of the paper I cited in this article. His comment points us to some useful links with some explanation of the problem.

I've spent a large part of the past twenty years dealing with geographically dispersed distributed systems whose components may cross national boundaries and whose sense of time must be very closely synchronized. That means [1] I've spent a lot of time studying ITU specifications, and [2] I'm kinda terrified by this.

This change has potential implications at many scales, from synchronization of communication channels (10^-9 seconds) to the ability to correlate events in log files (10^-2 seconds or thereabouts).

Thanks so much for the timely comment!

Jacque said...

I'm surprised that burning up all those trees in the Amazon hasn't dealt with enough mass to fix the problem.

Oh, wait; the rising sea-level due to global warming compensated. Oops.


Chip Overclock said...

Actually, all those paltry chemical reactions don't change the total mass of the planet. You have to set a nuke off to do that!