The Earth is spinning faster and faster and no one knows why

The Earth rotates once every 24 hours. This is the method used by the file Duration today. However, the reality is a bit more complicated. Because our planet is not completely static. Over time, it tends to spin less and less quickly. This usually runs in milliseconds. But for several years, it seems that the Earth wants, on the contrary, to Spin faster and faster.

As a result, June 29, 2022 was the shortest day on record atomic clocks. It went completely unnoticed because the day in question lasted only 1.59 milliseconds less than 24 hours classics. That’s still shorter than the record for the shortest day ever set… July 19, 2020. Her time was 1.47 milliseconds less than 24 hours. This record was broken again on July 26, 2022. With a day shorter by 1.50 milliseconds.

The issue of oscillation of the Earth’s rotation axis?

But what is happening to the earth? Several factors can cause Speed around which our planet revolves. The tidal forcesThe climate and the melting polar ice or internal movementsatmosphere from our land. Even the movement of our satellites. The mechanism is difficult to disassemble. No one has any certainty yet as to the origin of the current acceleration.

Some believe it is related to the Chandler Oscillation. This oscillationEarth’s rotation axis lead to irregular movement geographical poles on the surface of the globe. About three to four meters. But between 2017 and 2020, this fluctuation seems to have just disappeared.

Whatever the origin of the shortening of days, if the phenomenon continues, it will be necessary to consider the introduction of a negative leap second. To keep our clocks in sync with the sun. With the danger of it “skip again” It poses some problems for our computer systems. But according to experts, we’re not there yet. There is already a 70% chance that we have reached the minimum in the duration of the day…

The Earth accelerated its rotation in 2020!

In 2020, for the first time since measurements began 50 years ago, the Earth is spinning faster than usual. Scientists predict that it will be the same in 2021. Will we resort to a leap second to reset time? Ask the question.

Article from Natalie Meyer Posted on 01/15/2021

We all wanted to get this over with as quickly as possible. year 2020. It seems that even the Earth has done everything in its power to make it happen. It started spinning a little faster than usual. Until then, the record for the shortest day was held on July 5, 2005. Then our planet ran itself at 1.0516 milliseconds less than the average of 86,400 seconds per day. In 2020, this record was broken… 28 times! July 19 set a new record with a shorter day of 1.4602 milliseconds.

Nothing to worry about with that. A number of circumstances may cause Earth’s rotation speed. The movements of his heart, oceans and atmosphere. And even more. Moreover, on 27 occasions since 1972, it has been necessary to resort to the leap second to reset the astronomical time and the time provided by atomic clocks. In 2016, a second was added on December 31 at 23 hours 59 minutes 59 seconds.

Remove leap seconds?

But while the international community questions the merits of this principle, scientists are wondering for the first time whether it will be necessary to remove a second leap. Because in 2021 they are waiting The Earth rotates at least at the same speed.

According to their calculations, in 2021 the average day should last 0.07 milliseconds less than the average of 86,400 seconds. July 9 may set a new record with a day shorter than 1.88 milliseconds. Throughout the year, it was a file atomic clocks It can accumulate a delay of about 24 milliseconds. But in principle, the use of the leap second occurs only when the difference in the length of the day exceeds 400 milliseconds. So in 2016, we passed 490 milliseconds.

One more second in 2016: When the Earth slows down

It is known that the time has comesilver. In order to maintain consistency between the time of the atomic clocks and the exact time of the Earth’s rotation, which is not fixed, an additional so-called leap second will be added on December 31, 2016.

Article from Laurent Sacco Published on December 30, 2016

Since 1972, the Central Bureau of International Earth Rotation and the Reference Systems Service at the Paris Observatory have intermittently added seconds back to UTC (UTC). Earth’s rotation, which is used to determine Universal Time (UT) from the direction of the Earth with respect to stars, is not stable over time. So it is necessary to make adjustments if we want to agree with Coordinated Universal Time (UTC), which is more stable because it depends on atomic clocks.

It must be kept in mind, however, that changes to Earth’s rotation It is not done regularly. Thus, the second of cosmic time to be added does not result from a constant decrease in the speed of rotation of our planet. As a result, this addition may take place over several years in a row or, conversely, it may be postponed indefinitely. It may be that one day we’ll be led to ask again.

The leap second time is calculated…

However, since the introduction of this system, we have had to add 26 seconds to UTC. These additions are generally scheduled for either January 1st or July 1st at midnight. A 27^e A transition is planned from 2016 to 2017.

adding leap second Doomed to disappear due to the globalization of exchanges with Internet And the use of satellites, especially with GPS, does not adapt well to a time that does not depend solely on atomic clocks. However, the disappearance of UT in favor of Coordinated Universal Time (UTC) will be accompanied by other problems that must be resolved. In the meantime, the practice of the leap second is maintained at least until 2023.

One second in 2005

Paris Observatory article published on 12/30/2005

On January 1, 2006, at 1 am, the clocks will have to be pushed back for a tiny second. Very exceptionally, a minute between midnight will take 59 minutes and 1 hour 1 second longer than usual, 61 seconds instead of 60. So any watch that calculates the usual 60 seconds for this minute will return “1 hour” with a second in advance, and will have to be corrected, at least for For those who need the legal time to the nearest second.

In the UTC international time scale, this extra second, or “leap” second as it is called, will occur on December 31, 2005 just before midnight. Therefore scholars tend to consider that it belongs to the year 2005. But in France, due to the time difference compared to UTC during daylight hourswinter (+1h), it will arrive already at 1 AM on January 1st…2006.

This second takes place at the Paris Observatory. Indeed, the Division of Space-Time Reference Systems – SYRTE, through its activities in the fields of Earth rotation and time measurement, plays a major role in this event.

The rotation of the Earth on itself, which determines the passage of days and nights, slows down in the long run, mainly due to the effects of lunar gravitation. In addition, our planet is disturbed by its internal components (the core, Coat) and external (atmosphere and oceans).

However, time today is measured by means insensitive to the Earth’s mood, thanks to 250 atomic clocks belonging to several countries in the world, including 25 in France. Together, they make it possible to calculate Coordinated Universal Time – UTC (1).

The Coordinated Universal Time is so regular that it appears at a speed that shifts between it and the time of day and night determined by the Earth’s rotation on itself.

This delay may be annoying to some appsan international agreement signed in 1972 that states that the difference between the two should not exceed one second (2). C’est à cela que servent les secondes intercalaires : quand le décalage entre UTC et le temps lié à la rotation de la Terre s’approche d’une seconde, l’insertion d’une seconde intercalaire dans UTC permet de recaler ces deux chelles between them.

The Paris Observatory provides scientific services entrusted by national and international organizations. In this capacity, a component of the International Earth Rotation and Reference Systems Service – IERS, located at SYRTE, is responsible for predicting and announcing these leap seconds. This decision is then implemented by the international and national authorities responsible for broadcasting the time.

A long-term slowdown in the speed of Earth’s rotation since 1830 (in red).
The pink curve represents the effect of the Earth’s fluid core.

For France, it is LNE-SYRTE (3) Who is responsible for this task? This other component of SYRTE produces the Coordinated Universal Time of the Paris Observatory – UTC (OP). This high-precision reference is used by the France Telecom speaking clock, housed in the Paris Observatory, to broadcast French legal time; It can be listened to by calling 3699. The legal time based on UTC (OP) is also transmitted transparently by coding on the France Inter carrier wave, so that it can be used at any time by laboratories, industrialists, societies, etc. , everywhere in urban France (4).
International discussions that have been going on for several years could potentially lead to a modification of this system. The Coordinated Universal Time (UTC) would then be separated from the Earth’s rotation and we would no longer have to add leap seconds.

Notes:

(1) International Bureau of Weights and Measures – BIPM, the international body located in Sèvres, responsible for calculating Coordinated Universal Time (UTC). This is called a “paper” time scale, defined by a delay of up to 6 weeks. Any country that needs to measure effective time must make its own approximate version of UTC in real time. For France, this reference is the Coordinated Universal Time of the Paris Observatory – UTC (OP).

(2) Until 1960, a second unit was defined as the 86400th part of the mean solar day of 1900. Today it is defined as 9,192,631,770 periods of radiation corresponding to the transition between two superfine ground state levels.corn From cesium 133.

(3) Creates a framework contract between the National Laboratory of Measurement and Testing – LNE, the Paris Observatory and the National Center for Scientific Research, within SYRTE, LNE-SYRTE, which is a laboratory responsible for producing and making available national references to time measurements and frequencies.

(4) A partnership between the French Chamber of Watchmaking and Microtechnology – CFHM and LNE operates this medium for broadcasting legal time.