💾 Archived View for gmi.noulin.net › mobileNews › 3525.gmi captured on 2023-06-14 at 16:24:36. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2023-01-29)
-=-=-=-=-=-=-
2011-11-04 06:24:32
4 November 2011 Last updated at 06:06 GMT
Time, as we know it, could soon be in for a radical change.
This week, scientists at the Royal Society are discussing whether we need to
come up with a new definition of the world's time scale: Coordinated Universal
Time (UTC).
And the main issue up for debate is the leap second - and whether we should
abolish it.
The leap second came into existence in 1972. It is added to keep the time-scale
based on atomic clocks in phase with the time-scale that is based on the
Earth's rotation.
Atomic clock (NPL) Atomic clocks are much better at keeping time than the Earth
The reason for this is that while atomic clocks, which use the vibrations in
atoms to count the seconds, are incredibly accurate, the Earth is not such a
reliable time-keeper thanks to a slight wobble as it spins on its axis.
Rory McEvoy, curator of horology at the UK's Royal Observatory in Greenwich,
explained: "Since the 1920s, it has been known, and previously suspected, that
the motion of the Earth is not quite as constant as we'd first thought."
This means that time based on atomic clocks and time based on Earth drift ever
further out of phase over time.
So every few years, before the difference has grown to more than 0.9 seconds,
an extra second - called the leap second - is added to snap the two back into
synch.
"The International Earth Rotation Service monitors the Earth's activity, and
they decide when it is appropriate to add a leap second into our time-scale,"
said Mr McEvoy.
Split second
Continue reading the main story
Start Quote
Leap seconds are a nuisance
Felicitas Arias BIPM
But the call to get rid of the leap second is causing a rift within the
international time community, and it will come to a head at a vote at the World
Radio Conference of the International Telecommunication Union (ITU) in January
2012 in Geneva.
An informal survey by the ITU earlier this year revealed that three countries -
the UK, China and Canada, are strongly against changing the current system.
However 13 countries, including the Unites States, France, Italy and Germany,
want a new time-scale that does not have leap seconds. But with nearly 200
member states, this still leaves many others that have yet to reveal their
position.
The International Bureau of Weights and Measures (BIPM) in Paris is the
international standards organisation that is responsible for maintaining the
world's time. It thinks that the leap second should go because these one second
adjustments are becoming increasingly problematic for systems that need a
stable and continuous reference time-scale.
Clockface The leap second is troublesome for applications that require constant
time
Dr Felicitas Arias, director of the BIPM's time department and co-organiser of
the meeting at the Royal Society, explained: "It is affecting
telecommunications, it is problematic for time transfer by the internet (such
as the network time protocol, NTP) as well as for financial services.
"Another application that is really very, very affected by the leap second is
time synchronisation in Global Navigation Satellite Systems (GNSS).
"GNSS rely on perfect time synchronisation - and leap seconds are a nuisance."
One problem is that because the changes in the Earth's rotation are not
regular, leap seconds are also erratic, and only six months' notice is given
for each one.
Diverging time
But the countries that are against losing the leap second, including the UK,
say the problems are being exaggerated.
Peter Whibberley, senior research scientist in time and frequency at the
National Physical Laboratory, in Teddington, said: "When the UK government did
a survey of government agencies, they couldn't find anyone who was concerned
with leap seconds. So we don't see the evidence presented for the problems
caused by leap seconds as being all that serious."
But decoupling civil time from the Earth's rotation could also have longer-term
consequences.
Dr Whibberley explained: "[If you lost leap seconds] UTC would drift apart from
time based on the Earth's rotation, it would gradually diverge by an increasing
amount of time. Something would have to be done to correct the increasing
divergence."
Earth Unlinking time from the Earth's rotation has long-term consequences
Over a few decades this would amount to a minute's difference, but over several
hundred years this would mean the atomic clock time-scale and the time-scale
based on the Earth's rotation would be out by an hour.
In 2004, the idea of swapping leap seconds for a leap hour in a few hundred
years' time was proposed. But Dr Whibberley said most scientists agreed that
this would be even more problematic.
He explained: "It was dropped quickly. The general feeling was that you could
never implement a leap hour as they are much harder to do than the leap
seconds, and if you can't cope with leap seconds, it would be much harder to
cope with a leap hour."
One possible solution, if the leap second is abolished, could be to tie in any
changes with daylight saving changes - even though this would take place in a
few centuries' time.
"Countries could just accommodate the divergence by not putting their clocks
forward in the spring, so you'd change your time zone by one hour to bring
civil time back into line with the Earth's rotation," added Dr Whibberley.
Dr Arias said it was looking increasingly likely that leap seconds may be voted
out in January, but that the meeting at the Royal Society could help to thrash
out ideas that could offset any problems this loss could cause.
"The point is we can find a compromise, there are possibilities of leaving the
time open for synchronisation in the future," she said.