Think a second, before leaping! – Part 2
This lag of astronomical time behind UTC is why scientists resort to the leap second. “The reason we have to add a second every now and then,” Time and Date.Com explains, “is that Earth’s rotation around its own axis, and is gradually slowing down…”
By contrast, the website continues, “Atomic clocks…tick away at pretty much the same speed over millions of years. Compared to the Earth’s rotation, atomic clocks are simply too consistent”.
Paraphrasing Thales Group, the effect has been to change our relationship to time. The world no longer measures time against the movement of the Earth but against the energy cycles of atoms, such as caesium-133.
Since atomic cycles run independently of planetary rotation, UTC must occasionally be synchronized with UT1. The monitoring body is the International Earth Rotation and Reference System Service (IERS), with its Central Bureau in Frankfurt, Germany.
Once the difference between the time-scales exceeds 0.9 seconds, IERS will liaise with the International Bureau of Weights and Measures (BIPM), in France, to schedule an insertion: Giving affected entities, worldwide, a maximum six month notice.
Conventionally, the exercises occur June 30 or December 31, at three-year intervals. But intercalations aren’t compulsory; and insertions are infrequent. The most recent adjustment was last year—the 26th since leaping started, in 1972.
“If this were not done,” End Run Technology insists, “eventually UTC would drift out-of-sync with Earth’s day and many astronomical and navigational problems would ensue”. We’d soon notice the difference in Internet access, cell-phone performance, air traffic control systems, etc.
Still, not all time operatives and experts endorse the procedure. In fact, there is a groundswell of resistance, globally, to leap second exercises—and, according to Time and Date.Com, “several proposals have been put forward to abolish them”.
In the opinion of NIST’s Judah Levine, the insertions amount to a treatment that is worse than the cure: “Keeping the difference between Universal Time (UT1)…and UTC smaller than 1 second is not worth the difficulties…and I would advocate discontinuing leap seconds…”
Foremost among the “difficulties,” is the irregularity of the procedure: Which, Levine and his camp contend, is disruptive and destabilizing to many computerized systems. There is no fixed schedule or predictable pattern—and affected systems are given only six months warning.
After a 2012 intercalation, several major commercial systems crashed. These, says David Goldman, of CNN Money, included Linkedin, Four Square, Gawker and Reddit. Qantas Airline’s entire computer system went down, “forcing employees to check in passengers by hand”.
The ultimate fate of the leap second lies with the International Telecommunications Union (ITU) whose former Secretary-General, Hamadoun I. Toure, outlined the issues in a 2013 edition of ITU News.
Writing editorially, Toure, a Malian, observed that, “Some organizations involved with space activities, global navigation satellite systems, metrology, telecommunications…and electric power distribution have requested a continuous [that is, atomic] time-scale”.
But for “other specialized systems and for local time-of-day,” he continued, “A time-scale reckoned with respect to the rotation of the Earth is needed. Also, a change in the reference time-scale may have operational and hence economic consequences”.
The conflict pits Russia, former Soviet Bloc States, the United Kingdom and Arab countries, against the U.S.A. and a global armada of industrialized nations (including China, Japan, France and Australia), who would like to ax the leap second.
“Leap seconds” was hotly debated at ITU’s Conference in Geneva, Switzerland, and last November. But it put off a decision until 2023, for “further studies regarding current and potential future reference time-scales, including their impact and applications”.
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