2023-11-14 07:04:43
Using a device using the propagation of laser beams, researchers have measured for the first time the Earth’s rotation speed and its fluctuations with a precision of 9 decimal places. An important result for many scientific fields.
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[EN VIDÉO] Why don’t we feel that the Earth is rotating? The Earth completes one revolution on its axis in 24 hours, which corresponds to…
Everyone knows that the rotation of the Earth is 24 hours, and it takes our Planet 365 days to go around the Sun. If these values are more than sufficient to organize our daily routine, many scientific fields nevertheless need much more precision. Especially since neither the length of a day nor the period of revolution around the Sun are stable. Quantifying these tiny variations is particularly necessary for researchers who establish climate models, but also for astronomers.
The Earth’s rotation speed is influenced by the presence of a liquid envelope
The Earth is not in fact a completely solid body. It has several layers, one of which is liquid: this is the outer core. Perhaps you have already tried the hard-boiled egg and raw egg test? By rotating the two eggs, we realize that the presence of liquid influences the rotation of the raw egg. At a much higher scale of complexity, the same is true for Earth. The presence of a liquid envelope, which is also not necessarily homogeneous or regular, influences its rotation speed, but also the stability of its axis. The mass movements induced by the movement of this liquid mass thus accelerate or slow down the rotation of the Planet. These fluctuations, which we have known for a long time, have however just been quantified in an extremely precise manner thanks to a new device developed by the Wettzell Geodetic Observatory (Technical University of Munich). It is a ring-shaped laser system whose algorithm has been corrected to allow greater measurement precision.
The speed of rotation of the Earth with a precision of 9 decimal places
Within a hermetic enclosure equipped with mirrors, two laser beams are generated, one propagating clockwise, the other counterclockwise. If the Earth were stationary, the two beams would travel the same distance before meeting. But the movement of the Earth in space will induce a tiny movement of the mirrors: one of the laser beams will have a greater distance to travel than the other. This difference can be measured very precisely. It depends in particular on the speed at which the Earth rotates. For the first time, researchers were able to measure these variations in rotation speed with a precision of 9 decimal places! The results were published in the journal Nature Photonics.
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