The English Time and Date website explains in an article of July 28, that this acceleration is the last “in a series of speed records since 2020”. Christian Bizouard indicates that “since 2016, we have noticed that the rotation speed of the Earth is accelerating, and therefore the length of the day is decreasing! The astronomer studies this phenomenon within the Sirte research laboratory (Time-space reference systems), and explains that this observation is, to say the least, unexpected in view of past observations. “Since 1830, we observed a decrease in the speed of rotation of the Earth. This trend has been reversed for seven years without being able to explain it. Thus, the fastest 28 days since 1930 were recorded in 2020.
2 milliseconds
This variation does not worry the French astronomer since the Earth’s rotation has always been irregular. Its duration increases by about 2 milliseconds every century.
For Christian Bizouard, “80% of the variations in the speed of the Earth are linked to the winds”. Another cause is the tides, which are strong enough to produce 10 to 20% of the variations in rotation time.
But other fluctuations are difficult to explain. “It is thought to be due to internal movements in the Earth, the molten magma under the mantle. But we do not have any observations of the hard core, like those made in the atmosphere, which would validate these hypotheses. “ The scientist specifies however that to affirm that the global warming is in question, would be “pure speculation”.
Set clocks
If we don’t have to worry about this acceleration, for the international timekeepers, who allow us to set our clocks, that’s another story. These use ultra-precise atomic clocks to measure Coordinated Universal Time (UTC). Thus, since “1972, the International Earth Rotation and Reference Systems Service has regularly added a “leap second” to the year, at the end of June or the end of December. There have been 28 so far. The last dates back to December 31, 2016.” The recent acceleration of the Earth could thus call this process into question, as Christophe Bizouard explains: “For the first time, if the Earth continues to accelerate, we could be led to remove a second. It never happened. »