These times the earth turns a little faster

In recent years, the days have lasted shorter. For example, Astrophysicists do not understand why, since for billions of years they have lengthened. However, August 5 will be one of the shortest days of the year.

Posted at 8:00 p.m.

“The day will have 1.3 to 1.5 milliseconds less on August 5, compared to August 4,” says Robert Lamontagne, astronomer from the University of Montreal retired. Similarly, “In everyday life, you and I will not see the difference. Meanwhile, But it has an impact on GPS and stock market transactions. Furthermore, If we do not correct the clocks, there can be a variation of several hundred these times earth turns little meters with the GPS. However, This is why satellites that allow GPS to work are related to these precise ultra clocks.

Since 2020, the days are increasingly short because the earth has been turning faster on itself. Meanwhile, “It goes against the slowdown in the speed of rotation of the earth that has been measured for millions. In addition, even billions of years,” emphasizes Lamontagne. For example, We have geological evidence that at the time of dinosaurs. for example, 100 million years ago, the days had 23 hours rather than 24. Additionally, For example, And 900 million years ago, it was 10 p.m. In addition, »»

Add seconds – These times earth turns little

This very gradual lengthening of the days had pushed the service of reference systems of the rotation of the earth (ISRS) to introduce. Therefore, in 1972, an additional these times earth turns little second, called “interlayer”, this year, which has been done 24 other times since. Furthermore, The last addition of a second to a year took place in 2016.

“There are 400 atomic clocks around the world and the official hour is the average of all these clocks,” explains Mr. Consequently, Lamontagne. Meanwhile, When there is a slightly too large gap between the rotation of the earth. the time of atomic clocks, we adjust all the clocks. It is a complicated operation today because of all the computer systems that depend on a very precise hour. so there are people who offer to abandon synchronism between the rotation of the earth and the atomic clocks. »»

Earthquakes and climate

The reason for this trend reversal, which is now shortening the days, is not clear. “In physics. there is these times earth turns little a well-known principle which is the conservation of the angular moment,” says Lamontagne, who was also director of the Telescope of the Mont-Mégantic Observatory. “When an artistic skater ends his pirouette on himself, he folds his arms along his body and turns faster. It is a question of center of mass. We have seen for example that after significant earthquakes. in Chile and Haiti in 2010, in the days that followed, the earth turned faster of a millionth of a second. People have suggested that climate change is responsible for shortening days in recent years. If sides of the ice floe fall into the water, it changes the distribution of fluids on our planet. »»

The shortening of the days is minimal. “We are talking about one to two milliseconds in total, less than a beat of eyelashes,” says Robert Lamontagne. Furthermore, »»

But because of this trend, ISS plans to remove a second for one day, in 2028 or 2029.

The phenomenon was for the first time demonstrated by astronomers from the State University of Moscow. in 2022, in the Journal of Geophysical Research.

This extension until 2020, then shortening, is not a long, quiet river. “We agree that the rotation period of our planet, it fluctuates,” observes Mr. Lamontagne. We often compare this to the fluctuations in the stock markets. On average, they climb by 5 % per year, but we know that there are excursions up or down. Or even the temperature of the seasons: we have global warming, but some years will still be colder than others. »»

Deformation

This variability is due to the form and these times earth turns little composition of the earth. “If our planet was a solid pumps on the surface. perfectly spherical and all alone in the cosmos, its period of rotation would be extremely stable,” notes the astronomer. But this is not the case. The diameter measured at the equator is 43 kilometers larger than at the poles. There is magma that moves inside the earth. And there is also a lot of surface water. It is the same as for road trains: if the equipment is not stowed inside. the vehicle will pitch from one side to the other depending on the vagaries of the road. »»

How do we manage to predict the duration of the day of August 5? “The moon has already found itself in a similar position recently,” explains Mr. Lamontagne. The duration of the days observed during these recent episodes can therefore serve as these times earth turns little an indicator. The moon influences the tides and also exercises an attraction on the earth which modifies its rotation.

The moon was in a similar position on July 9 and 22. But finally, the shortest day at the beginning of the month was rather on July 10, with 1.38 millisecond less than normal, according to a columnist from Weather Channel.