| LONDON, June 29
LONDON, June 29 The world is about to get a
well-earned long weekend but don't make big plans because it
will only last an extra second.
A so-called 'leap second' will be added to the world's
atomic clocks as they undergo a rare adjustment to keep them in
step with the slowing rotation of the earth.
To achieve the adjustment, on Saturday night atomic clocks
will read 23 hours, 59 minutes and 60 seconds before moving on
to midnight Greenwich Mean Time.
Super-accurate atomic clocks are the ultimate reference
point by which the world sets its wrist watches.
But their precise regularity - which is much more constant
than the shifting movement of the earth around the sun that
marks out our days and nights - brings problems of its own.
If no adjustments were made, the clocks would move further
ahead and after many years the sun would set at midday. Leap
seconds perform a similar function to the extra day in each leap
year which keeps the calendar in sync with the seasons.
The grandly named International Earth Rotation and Reference
Systems Service (IERS) based in Paris, is responsible for
keeping track of the gap between atomic and planetary time and
issuing international edicts on the addition of leap seconds.
"We want to have both times close together and it's not
possible to adjust the earth's rotation," Daniel Gambis, head of
the Earth Orientation Centre of the IERS, told Reuters.
Gambis said the turning of the earth and its movement around
the sun are far from constant.
In recent years a leap second has been added every few
years, slightly more infrequent than in the 1970s despite the
long-term slowdown in the earth's rotation caused by tides,
earthquakes and a host of other natural phenomena.
Adjustments to atomic clocks are more than a technical
A collection of the highly-accurate devices are used to set
Coordinated Universal Time which governs time standards on the
world wide web, satellite navigation, banking computer networks
and international air traffic systems.
There have been calls to abandon leap seconds but a meeting
of the International Telecommunications Union (ITU), the U.N.
agency responsible for international communications standards,
failed to reach a consensus in January.
"They decided not to decide anything," says Gambis, adding
that another attempt will be made in 2015.
Opponents of the leap second want a simpler system that
avoids the costs and margin for error in making manual changes
to thousands of computer networks. Supporters argue it needs to
stay to preserve the precision of systems in areas like
Britain's Royal Astronomical Society says the leap second
should be retained until there is a much broader debate on the
"This is something that affects not just the telecom
industry," said RAS spokesman Robert Massey. "It would decouple
time-keeping from the position of the sun in the sky and so a
broad debate is needed."
Time standards are important in professional astronomy for
pointing telescopes in the right direction but critical systems
in other areas, not least defence, would also be affected by the
"To argue that it would be pain free is not quite true,"
A decision is not urgent. Some estimate that if the current
arrangement stays, the world may eventually have to start adding
two leap seconds a year. But that is not expected to happen for
another hundreds years or so.
In the meantime, Massey plans to use his extra second wisely
this weekend. "I'll enjoy it with an extra second in bed," he
(Editing by Andrew Heavens)