January 20, 2012
Leap Seconds Get A Three Year Reprieve
An attempt to eliminate leap seconds and permanently change how time is measured has been postponed until 2015 by the International Telecommunications Union.
ITU Radio-communication Assembly delegates on Thursday were unable to come to an agreement on whether to stop adding leap seconds to the world´s atomic clocks to keep them synchronized with Earth´s rotational cycles.
The ITU will now spend the next three years conducting further studies “to ensure that all the technical options have been fully addressed” and to hold further discussions with its members.
The measure to eliminate leap seconds has been supported by leaders from the US, Canada, Japan, Mexico, France and Italy, while Germany and the UK strongly opposed such actions. Other member states said they would like to see more investigating before a decision is made.
Discussions at the ITU meeting “revealed a heightened degree of interest that has not previously existed on this issue,” Richard C. Beaird, a State Department official who led the American delegation, told NY Times in a statement.
Because no accord was reached among the delegates, the ITU -- part of the United Nations -- sent the issue back to a panel of experts for further study, said Beaird, adding that a revised proposal will be introduced no earlier than 2015.
He added that the delay was “a significant step forward” and that the burst of interest in leap seconds “should allow for a decision that will have the widest possible backing.”
The ITU in a statement said its Secretary-General, Hamadoun TourÃ©, considered the move to postpone the decision would “ensure that all stakeholders have been adequately associated with a step which will clearly influence our future.”
Introduced in 1971, leap seconds keep the Coordinated Universal Time (UTC) accurate; UTC is measured using the rotation of the planet and super-accurate International Atomic Time (TAI). Because Earth´s spin is continually slowing down, leap seconds are added every so often to bridge the gap between the atomic clocks and the time according to the planet´s rotation.
Supporters of the measure to assassinate leap seconds argue that they are unworkable in the long-term and are an unnecessary addition for systems relying on precise time measurements.
Vincent Meens, who headed the ITU group recommending the removal of leap seconds, said not having to introduce leap seconds every few years would give us “a more standard time than the one we have today.” He told reporters at the meeting that time is “very, very important for synchronization of all the radio communications systems. For instance, a lot of systems are using GPS time just to synchronize themselves and that would be very important for everybody to have the same time,” referring to satellite navigation systems.
Stopping their systems for the length of a heartbeat every few years is disruptive and potentially dangerous, added Elisa Felicitas Arias, director of the time department at the Paris-based International Bureau of Weights and Measures.
“You can make a dramatic error if, for example, you are trying to land an aircraft,” she told the Associated Press (AP), noting that rocket launches, too, are never scheduled on days when a leap second might occur. “This is something we are trying to correct.”
“Most of the people who operate time services favor discontinuing leap seconds,” Judah Levine, a physicist at the National Institute of Standards and Technology in Boulder, Colorado, told AP. “The main problem is that the leap second is usually implemented by stopping the clock for one second. However, the world doesn´t stop.”
Opponents of disabling leap seconds claim there is a lack of solid evidence to suggest that serious problems can occur by adding a second to the world´s atomic clocks. They further counter that computers can easily cope with delaying time for a brief moment.
Decoupling UTC from the rotation of the Earth would bring to an end a millennia of telling time using the spin of the Earth as it orbits the Sun.
The ITU said eliminating leap seconds would also eliminate the need for what it calls “specialized ad-hoc time systems.” It did say, however, that it may have “social and legal consequences when the accumulated difference between UT1 - Earth rotation time - would reach a perceivable level - two to three minutes in 2100 and about 30 minutes in 2700.”
P. Kenneth Seidelmann, a University of Virginia professor who has argued in favor of leap seconds, said he is pleased with the postponement. The study panel had been working on this measure for more than a decade without reaching consensus. “What are they going to accomplish in the next three?” he asked.
Over the past 40 years, 34 seconds have been added to UTC. The last leap second occurred in 2008. The next one will be added to clocks this year at the end of June.
On the Net:
- International Telecommunications Union
- International Bureau of Weights and Measures
- National Institute of Standards and Technology