Les journées sur Terre deviennent-elles plus longues ? © Qimono, Pixnio

Day length on Earth is getting longer and scientists can’t explain why

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Since atomic clocks associated with precise astronomical measurements have recently revealed that the duration of a day on Earth suddenly lengthened. This phenomenon has critical implications not only for our measurement of time, but also for things like gps and other technologies that govern our modern lives.

In recent decades, the Earth’s rotation around its axis, which determines the length of a day, has accelerated. This trend has shortened our days; in fact, in June 2022 we have reached the record of the day shorter for about half a century.

But despite this record, since 2020, this constant acceleration has curiously turned into a slowdown: the days are longer again, and for the moment the reason is unknown.

While the clocks on our phones show that a day is exactly 24 hours long, the actual time it takes for the Earth to complete a single rotation varies very slightly. These changes occur over periods ranging from millions of years to almost instantaneously, even earthquake and No precise features for…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/b/9/7/b97fffc285_117970_tempete-littoral.jpg” data-url= ” https://news.google.com/planete/definitions/climatologie-storm-14551/” data-more=”Read more”>storms can play a role. So it turns out that a day very rarely corresponds to The list of magic numbers is: 8, 20, 28, 40, 50, 82, 126,…
For example, the isotope 208 of lead has 82…” data-url=”https://news.google.com/sciences/definitions/physics-magic-number-4576/” data-more=”Read More” >magic number of 86,400 seconds.

The ever changing planet

For millions of years, the Earth’s rotation has slowed down due to the frictional effects associated with tides caused by the moon This process adds about 2.3 milliseconds to the length of each day each century. A few billion years ago, an Earth day lasted only 19 hours.

For the past 20,000 years, another process has worked in reverse, speeding up the Earth’s rotation. At the end of the last Origin of the Quaternary glaciations
The…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/c/9/0/c9095f93f2_50015412_map-pleistocene-glaciation-north-arizona-university-dr.jpg” data-url=”https://news.google.com/planet/definitions/climatology-ice-period-1068/” data-more=”Read more”>ice AgeCast iron, an alloy of iron and carbon
There is still a bit more carbon in the…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/2/9/0/2906dda4fe_108336_fonte-theiere. jpg” data- url=”https://news.google.com/sciences/definitions/chimie-fonte-16520/” data-more=”Read more”>melting since polar ice caps reduced the Pressure at the surface, and the mantle, solid though it may be, is animated by convection currents that…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/4 / 6 /7466fb8049_50004180_earth-270907.jpg” data-url=”https://news.google.com/planet/definitions/structure-earth-earth-mantle-2495/” data-more=”Read More”>earth’s mantle began to move steadily toward the poles.

Just as a ballet dancer spins faster when she brings her arms closer to her body – the axis around which she spins – the Rotation speed of our planet increases when this dough of the mantle approaches the axis of the Earth. And this process shortens each day by about 0.6 milliseconds per century.

For decades and more, the connection between the Earth’s interior and the surface also comes into play. Large earthquakes can change the length of the day, though usually by small amounts. For example, him great tohoku earthquake 2011 in Japan, at magnitude 8.9, would have accelerated the Earth’s rotation by a relatively small amount 1.8 microseconds.

Apart from these large-scale changes, over shorter periods, time and heated They also have significant impacts on the Earth’s rotation, causing variations in both directions.

Bimonthly and monthly tidal cycles move mass around the planet, causing changes in day length of up to a millisecond in any direction. We can observe tidal variations in photoperiod records for periods up to 18.6 years. the movement of our atmosphere it has a particularly strong effect, and ocean currents also play a role. snow covered and precipitation seasonal or groundwater extraction changes things even more.

Using radio telescopes to measure the Earth’s rotation involves observing radio sources such as quasars. Turn on French subtitles by clicking the cogwheel, then Auto Translate, then Choice of Language. © NASA, Goddard

Why is the Earth suddenly slowing down?

Since the 1960s, when operators of radio telescopes around the planet began to devise techniques to simultaneously observe cosmic objects like quasarswe have very precise estimates of the speed of rotation of the Earth.

A comparison between these estimates and an Applications of Atomic Clocks
Its accuracy and stability are…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/6/6/c/66c91e0ab7_50038925_norman-f-ramsey-adrienne-kolb-fermilab – history-archives-project-03.jpg” data-url=”https://news.google.com/sciences/definitions/physics-atomic-clock-12827/” data-more=”Read More”>atomic clock revealed an apparently increasingly shorter day length in recent years.

But there is a surprising revelation once we remove the fluctuations in rotational speed that we know to occur due to tidal and seasonal effects. Although the Earth reached its shortest day on June 29, 2022, the long-term trajectory appears to have gone from shortening to lengthening since 2020. This change is unprecedented in the last 50 years.

The long-term trajectory appears to have changed from shortening to lengthening since 2020. This change is unprecedented in the last 50 years.

The reason for this change is not clear. It could be due to changes in weather systems, such as La Niña climatic phenomena consecutive, even if these have happened before. It could be a further melting of the polar ice caps, although these have not deviated much from their normal rate of melting in recent years. Could it be related to the great explosion of the The study of volcanoes is volcanology or volcanology. Volcanic activity is one of…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/d/c/f/dcfcbbf72e_125167_volcan-arenal-costa-rica. jpg” data- url=”https://news.google.com/planete/definitions/volcanologie-volcano-3537/” data-more=”Read more”>volcano tonga injecting large amounts of water into the atmosphere ? Probably not, considering it happened in January 2022.

Scientists have speculated that this mysterious recent change in the planet’s rotation rate is related to a phenomenon called “Chandler’s Swing” – a small deviation of the Earth’s axis of rotation with a period of about 430 days. Observations from radio telescopes also show that the wobble has decreased in recent years; the two phenomena could be related.

A final possibility, which seems plausible to us, is that nothing specific has changed on or around Earth. They could simply be long-term tidal effects that work in parallel with other periodic processes to produce a temporary change in the Earth’s rotation rate.

Do we need a “negative leap second”?

Precise knowledge of the Earth’s rotation rate is crucial for a host of applications: navigation systems like GPS wouldn’t work without it. Also, every two or three years, the timekeepers insert leap seconds on our official timescales to ensure they don’t get out of sync with our planet.

If Earth were to transition to even longer days, we may need to incorporate a “negative leap second,” which would be unprecedented and could break the internet.

The need for negative leap seconds is considered unlikely at this time. For now, we can rejoice in the news that, at least for a while, we all get a few extra milliseconds every day.

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