- 4412
- CLIMATE CHANGE
- time, of course it is
changing? - Climate change is messing with how we
measure time. It may have delayed the
need for the world's timekeepers to add a "negative leap second" to
standard time. Struggle to wrap your
head around daylight savings? Spare a thought for the world's timekeepers, who
are trying to work out how climate change is affecting Earth's rotation, and in
turn, how we keep track of time.
-
------------------------- 4412
- CLIMATE CHANGE
- time, of course it is
changing?
-
- In a strange twist, global warming could
even help out timekeepers by delaying the need for history's first
"negative leap second" by three years.
-
- Experts fear that introducing a negative
leap second, that is a minute with only 59 seconds, into standard time could
cause havoc on computer systems across the world.
-
- For most of history, time was measured by
the rotation of the Earth. However in 1967, the world's timekeepers embraced
atomic clocks, which use the frequency of atoms as their tick-tock, ushering in
a more precise era of timekeeping.
-
- But sailors, who still relied on the sun and
stars for navigation, and others wanted to retain the connection between
Earth's rotation and time. There was a
problem. Our planet is an unreliable clock, and had long been rotating slightly
slower than atomic time, meaning the two measurements were out of sync.
-
- So a compromise was struck. Whenever the
difference between the two measurements approached 0.9 of a second, a
"leap second" was added to “Coordinated Universal Time” (UTC), the
internationally agreed standard by which the world sets its clocks.
-
- Though most people likely have not noticed,
27 leap seconds have been added to UTC since 1972, the last coming in 2016.
-
- But in recent years a new problem has
emerged that few saw coming: Earth's rotation has been speeding up, overtaking
atomic time. This means that to bring
the two measurements in sync, timekeepers may have to introduce the first ever
negative leap second.
-
- What time is it? That depends if you are
looking at the Earth's rotation or atomic clocks. This has never happened before, and poses a
major challenge to making sure that all parts of the global timing
infrastructure show the same time.
-
- Many computer programs for leap seconds
assume they are all positive, so these programs would have to be rewritten.
-
- Using satellite data science determined that
if not for climate change, a negative leap second might have needed to be added
to UTC as soon as 2026. But starting
from 1990, melting ice in Greenland and Antarctica has slowed down the Earth's
rotation. This has delayed the need for a negative leap second until at least
2029.
-
- When the ice melts, the water spreads out
over the whole ocean; this increases the moment of inertia, which slows the
Earth down.
-
- Earth is too unpredictable to be sure if a
negative leap second would be needed any time soon. Melting polar ice has affected the Earth's
rotation since 1990. A negative leap
second would be a hop into the unknown.
-
- Even positive leap seconds have previously
caused problems for systems that require precise timekeeping. That is partly why the world's timekeepers
agreed in 2022 to scrap the leap second by 2035. From that year, the plan is to allow the
difference between atomic time and the Earth's rotation to grow up to a minute.
-
- A subsequent leap minute to bring them into
sync is not expected to be needed in the next century. And "a negative leap minute” is very,
very unlikely. This research may prompt
the world's timekeepers to consider dropping the leap second sooner than 2035.
-
March 29, 2023 CLIMATE
CHANGE - time, of course it is changing? 4412
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------ “Jim Detrick” -----------
--------------------- --- Saturday, March 30,
2024
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