The earth will turn a little faster on itself several times this summer: you will not feel it, but our planet will complete its daily rotation in just under 24 hours this Tuesday, of 1.38 millisecond less very exactly.
The phenomenon is observed three times this summer: on July 9, this Tuesday and August 5, which will be the shortest day of the year because that day, the earth will run on itself with 1.5 millisecond in advance.
An acceleration caused in part by the position of the moon, which will be the most distant from the equator. In theory, the rotation of our planet lasts 86,400 seconds, or 24 hours: we call it astronomical time.
This time is influenced by the moon, but also the melting of ice, earthquakes or volcanic activity. Yet long -term long -off, the rotation of the earth has tended to slow down for millions of years, because the gravitational forces between our planet and the moon play as a brake on the movement of the earth.
Two billion years ago, a day lasted … 20 hours. This extremely slow slowdown requires adapting our clocks. The time of reference in the world is the UTC, the coordinated universal time, which has as a starting point the Greenwich meridian. Since the 1960s, it has been based on atomic time, measured by hyperprecise atomic clocks.
To correspond to the real rotation of the earth, the International Earth Rotation Service adds what is called “second intercalale” for decades and this is done on the last day of June or the last day of the year.
Basically, at 11:59 p.m. and 59 seconds, we add an additional second to universal time. The clock then displays 11:59 p.m. and 60 seconds, and only, we spend at midnight the next day.
For us, that does not change anything but the operation is important for GPS systems and computer networks. Except that since 2020, the earth has tended to turn faster and faster: acceleration peaks like those that we observe this summer are more frequent and more marked.
The shortest rotation record was broken in July 2024, with 1.66 milliseconds in advance … And for the moment, scientists do not really know how to explain it. We assume that this is an internal phenomenon to our planet, but without certainty. The trend is such that the body responsible for unifying the pendulums of the whole world plans to introduce a negative second interlayer – withdraw a second – in 2029 and that would be a great first.
That said, this trend should quickly take place and resume the natural course – the slowdown in terrestrial rotation: astronomers predict that in 200 million years, a day will last 25 hours.
