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Wednesday, December 28, 2005

Adjustment Costs and Leap Seconds

With sticky prices, the more costly prices are to change, the less frequently they are adjusted. It turns out that measured time is sticky too. Now that the use of atomic clocks in GPS systems, telecommunications, and elsewhere has made it more costly to adjust clocks, there are proposals to reduce the frequency of adjustment. The current practice is to adjust the clocks when they are off by a second (i.e., their "S-s rule" is one second), but some would prefer to wait until clocks are off by as much as several minutes relative to the earth's rotation before any adjustment is made:

Second Thoughts, SciAm Observations: Plenty of sources (for example, the BBC) are reporting on the leap second that will be tagged onto the end of 2005. Daniel Engber's helpful Explainer column at Slate discusses why the world's official timekeepers occasionally fiddle with the length of a day to help keep clocks more in sync with the actual period of the Earth's rotation. (Tidal forces, ice ages, massive earthquakes and even meteorological phenomena can all shift the balance of our planet's mass around its axis and thereby speed up or slow down its spin.) However, generally overlooked in all this coverage is the interesting point that such leap seconds are becoming sources of friction between astronomers and the telecommunications sector, and there is a proposal to eliminate them. Wendy M. Grossman revealed why in a news story in the November issue of Scientific American: randomly extending and shortening days throws a wrench into the GPS system, which relies on atomic clocks, not astronomical time. How much of a problem that really poses is open to discussion; I see, though, that according to RIA Novosti, the Russian military is saying that the 2005 leap second will not affect its Strategic Missile Force. So... thanks for the reassurance on that, I guess.

Here's more from the linked article be Wendy M. Grossman:

To illustrate the issue posed by leap seconds, Levine points to navigation. "Every time there's a leap second, the thing that's moving continues to move, but the clock stops," he explains. "So the people who deal with physical processes do not want leap seconds." ... To keep clocks from drifting too far from the day-night cycle, abolitionists would presumably need to add, say, several leap minutes every few hundred years. The existing ... system, Levine notes, ... sows confusion. For one, the leap second occurs in the middle of the day in Asia and Australia, causing a time hiccup during stock trading. For another, the more timescales there are, the easier it is for a programmer to make an error in calculations. Astronomers are deeply dismayed at the prospect, which would decouple time from the earth's rotation...

    Posted by on Wednesday, December 28, 2005 at 06:32 PM in Economics, Science | Permalink  TrackBack (0)  Comments (1)


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