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Editorial


Front Page - Friday, February 26, 2016

Leap seconds lost in shuffle


I Swear



Vic Fleming

In late 2005, the world – including Tennessee and Arkansas – was told that Mother Earth had lost a moment or so, notwithstanding the hectic pace we’d been on for a decade. The solution was to add a leap second” to the intangible timepiece maintained by cosmic forces. 

That mathematical maneuver occurred on Dec. 31, 2005. This practice has become commonplace since being developed in 1972. 

So, what’d you do with your extra second? Mine got lost. I was looking for it the other day and learned that, by golly, we got another leap second added at 7:00 p.m. CST last year on June 30! I couldn’t find that one either. Sheesh! Give me a little extra time, and what do I do? I lose it.

Tackling this topic ten years ago, I cited Guy Gugliotta, writing in the Washington Post. For plagiarism protection, I hereby cite timeanddate.com as I revisit the subject.

So, occasionally a leap second is added to Coordinated Universal Time (UTC) in order to synchronize atomic clocks with the earth’s ever slowing rotation. It seems that atomic clocks are just too darned accurate. UTC is determined by the relative relationship between two factors (don’t doze off on me, now!): International Atomic Time (TAI) and Universal Time (UT1), also known as Astronomical Time.

TAI is a scale combining the output of some 200 highly precise atomic clocks worldwide. TAI tells us the exact speed at which our clocks are supposed to tick. UT1, on the other hand, is derived from the actual speed of the planet as it rotates, determining the actual length of a day. Yes, Virginia, there is a difference. And, it turns out, close enough for government work” would get us thrown off by a full day if we ignored the problem for, like, 500 centuries or so. 

As and when the difference between these two factors approaches 0.9 seconds, a leap second is added, to balance the … time sheets. The International Earth Rotation and Reference System Service (IERS), from its base in Paris, issues notifications alerting us when a leap second is to be added. Note to self: Pay attention next time! Every second counts.”

Reiterating, we add a second every now and then because our planet’s rotation on its own axis is gradually slowing down, whereas atomic clocks tick-tock tick-tock at a constant speed.

The first leap second was added in 1972; UTC was 10 seconds behind TAI then. Twenty-six leap seconds have been added altogether since this methodology was developed. This means that the earth has slowed down an additional 26 seconds compared to TAI since then; it does not mean that days are 26 seconds longer, just that the specific 26 days to which a second was added had 86,401 seconds, instead of the usual 86,400.

The length of an average day on Earth is increasing by about two milliseconds per century. That is due to the ever-slowing rotation. Scientists seem to agree that adding leap seconds is likely to become a twice-a-year experience by this time next century. So, be prepared to enjoy the extra time. And watch for those memos from IERS.

Vic Fleming is a district court judge in Little Rock, Ark., where he also teaches at the William H. Bowen School of Law. Contact him at vicfleming@att.net.