Earth is spinning faster now than it was 50 years ago, say scientists

Posted: February 3, 2022 by oldbrew in Measurement, moon, solar system dynamics
Tags: ,

Credit: NASA

Compensating for the lost time may prove challenging for scientists, says Astronomy magazine. Turning the internet clock back one second implies a repeat of a computer-generated timestamp for example, which might confuse some vital systems not designed to handle that.
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Ever feel like there’s just not enough time in the day? Turns out, you might be onto something.

Earth is rotating faster than it has in the last half-century, resulting in our days being ever-so-slightly shorter than we’re used to.

And while it’s an infinitesimally small difference, it’s become a big headache for physicists, computer programmers and even stockbrokers.
. . .
“As time goes on, there is a gradual divergence between the time of atomic clocks and the time measured by astronomy, that is, by the position of Earth or the moon and stars,” says Judah Levine, a physicist in the time and frequency division of the National Institute of Standards and Technology.

Basically, a year as recorded by atomic clocks was a bit faster than that same year calculated from Earth’s movement. “In order to keep that divergence from getting too big, in 1972, the decision was made to periodically add leap seconds to atomic clocks,” Levine says.

Leap seconds work a little like the leap days that we tack on to the end of February every four years to make up for the fact that it really takes around 365.25 days for Earth to orbit the Sun. But unlike leap years, which come steadily every four years, leap seconds are unpredictable.

The International Earth Rotation and Reference Systems Service keeps tabs on how quickly the planet spins by sending laser beams to satellites to measure their movement, along with other techniques.

When the time plotted by Earth’s movement approaches one second out of sync with the time measured by atomic clocks, scientists around the world coordinate to stop atomic clocks for exactly one second, at 11:59:59 pm on June 30 or December 31, to allow astronomical clocks to catch up. Voila — a leap second.

Unexpected change

Since the first leap second was added in 1972, scientists have added leap seconds every few years. They’re added irregularly because Earth’s rotation is erratic, with intermittent periods of speeding up and slowing down that interrupt the planet’s millions-of-years-long gradual slowdown.

“The rotation rate of Earth is a complicated business. It has to do with exchange of angular momentum between Earth and the atmosphere and the effects of the ocean and the effect of the moon,” Levine says. “You’re not able to predict what’s going to happen very far in the future.”

But in the past decade or so, Earth’s rotational slowdown has … well, slowed down. There hasn’t been a leap second added since 2016, and our planet is currently spinning faster than it has in half a century.

Scientists aren’t sure why.

“This lack of the need for leap seconds was not predicted,” Levine says. “The assumption was, in fact, that Earth would continue to slow down and leap seconds would continue to be needed. And so this effect, this result, is very surprising.”

The trouble with leap seconds

Depending on how much Earth’s rotations speed up and how long that trend continues, scientists might have to take action. “There is this concern at the moment that if Earth’s rotation rate increases further that we might need to have what’s called a negative leap second,” Whibberley says. “In other words, instead of inserting an extra second to allow Earth to catch up, we have to take out a second from the atomic timescale to bring it back into state with Earth.”

But a negative leap second would present scientists with a whole new set of challenges. “There’s never been a negative leap second before and the concern is that software that would have to handle that has never been tested operationally before,” Whibberley adds.

Full article here.

  1. […] Earth is spinning faster now than it was 50 years ago, say scientists […]

  2. Russell Cook (@QuestionAGW) says:

    More likely a result caused by Russian meddling than by global warming, I think …..

  3. oldbrew says:

    Could be the next computer ‘millennium bug’ scare 😎

  4. tom0mason says:

    “The rotation rate of Earth is a complicated business. It has to do with exchange of angular momentum between Earth and the atmosphere and the effects of the ocean and the effect of the moon,”
    I would also surmise that (small) changes Earth’s core movement, including flows of the liquid magma layer would affect the the Earth’s spin.

    Levine says. “You’re not able to predict what’s going to happen very far in the future.” .
    Obviously they need some of those remarkable people who can model climate to help them. 😉

  5. oldbrew says:

    NASA article on length of day…

    March 4, 2003

    Because of Earth’s dynamic climate, winds and atmospheric pressure systems experience constant change. These fluctuations may affect how our planet rotates on its axis, according to NASA-funded research that used wind and satellite data.
    . . .
    Because of the law of “conservation of angular momentum,” small but detectable changes in the Earth’s rotation and those in the rotation of the atmosphere are linked.

  6. If the Earth was gaining mass it would increase the speed of spin.

  7. Phoenix44 says:

    So it’s actually reversed what it was doing and what was predicted. So the previous explanation is unlikely to have been correct. Time to start again.

  8. oldbrew says:

    NASA data from 2000-2001. The LOD (length of day) line is a bit faint.


    This graph displays the close connection between the global angular momentum of the atmosphere derived from wind analyses (darker red curve, scale on right) and the observed changes in the length of day (lighter green curve, scale on left), after removing low frequencies, for the years 2000/2001. The remarkable agreement demonstrates that a close coupling exists between motions of the atmosphere and the solid Earth. CREDIT: Atmospheric and Environmental Research, Inc.
    – – –
    [Note: the version of the image in the NASA article has no colours]

  9. tallbloke says:

    Moving mass nearer to the spin axis would increase rotation rate, like the spinning skater pulling in their arms. Greenland and Antarctica are gaining more snow than they’re losing in meltwater perhaps?

  10. RoswellJohn says:

    Ha! Y2K got me a software job back in 1998! I’m too old to go back to software development now.

    However, if I remember correctly, having a long time interest in earth rotation, leap second announcements were concentrated during solar max periods, not solar minimums. Which would mean that the solar wind was causing a drag on the earth’s atmosphere and slowing it down during solar max periods.

    I have a meeting to attend in a few minutes: Could TB or OB do a quick graph of leap seconds and solar cycles? I’m amazed that the paper authors didn’t figure this out themselves! Thanks!

  11. RoswellJohn says:

    Well, I can’t paste a graph in here (no server to link to), but I did create one locally. There is some correlation between sunspot cycle and leap second announcements, but it’s not great. There were many more leap seconds in the 3rd and 2nd cycles back and fewer in the last one, but they weren’t exactly aligned with the maximums in the cycle. I did a search to see if anyone else had a graph I could link to, but it came up negative. So it hasn’t occurred to anyone else either. Apparently geomagnetic indices are a proxy for solar wind so I’ll try a search on that too.

  12. Gamecock says:

    “If the Earth was gaining mass it would increase the speed of spin.”

    Uhhh . . . no, that’s backwards.

    Anywho, nobody understands it, anyway.

    How many times does the earth rotate on its axis in a year? Clue: it’s not 365. Nor 365.25 for you pedants.

  13. Gamecock says:

    And, yes, after 4.5 billion years, the earth is still accreting material from space.

  14. Phil Salmon says:

    The most likely reason for shortening length of day (LOD) is increasing ice held at the poles. Mainly Antarctica.

  15. Tim Spence says:

    But what is a year, 365.25 rotations or 1 orbit of the Sun? It’s both according to the Mirriam-Webster !
    An Earth day was about 23 hours at the end of the Cretacious and about 22 hours at the beginning of the Triassic. And yet the Earth slows as the Moon moves further away, it’s a mystery to me.

  16. oldbrew says:

    Less than 5 years ago…

    Nov 20, 2017
    Earth’s Rotation Is Mysteriously Slowing Down: Experts Predict Uptick In 2018 Earthquakes

  17. oldbrew says:

    Decadal variations in geophysical processes and asymmetries in the solar motion about the Solar System’s barycentre
    May 2010

    In addition, Ian Wilson (Sidorenkov and Wilson 2009) shows that, from 1700 to 2000 A.D., on every occasion where the Sun has experienced a maximum in the asymmetry of its motion about the centre-of-mass of the Solar System, the Earth has also experienced a significant deviation in its rotation rate (i.e. LOD) from that expected from the long-term trends. This fact indicates that the changes in the Earth’s rotation rate are synchronized with a phenomenon that is linked to the changes in the solar motion about the barycentre of the Solar System. [bold added]

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