Using a device that uses the propagation of laser beams, researchers have for the first time measured the Earth’s rotation speed and its fluctuations with an accuracy of nine decimal places. An important result for many scientific areas.
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[EN VIDÉO] Why don’t we feel the earth turning? The Earth completes one revolution on its axis in 24 hours, which…
Everyone knows that the Earth’s rotation lasts 24 hours and our planet takes 365 days to orbit the Sun. If these values are more than sufficient for organizing our everyday lives, many scientific areas still require much more precision. Especially since neither the length of a day nor the period of rotation around the sun are stable. Quantifying these tiny variations is particularly necessary for researchers who create climate models, but also for astronomers.
The Earth’s rotation speed is influenced by the presence of a liquid shell
In fact, the Earth is not a completely solid body. It consists of several layers, one of which is liquid: this is the outer core. Maybe you’ve tried the hard-boiled egg versus raw egg test? By rotating the two eggs, we see that the presence of liquid affects the rotation of the raw egg. On a much higher scale of complexity, the same is true for Earth. The presence of a fluid shell, which is also not necessarily homogeneous or regular, affects its rotation speed but also the stability of its axis. The mass movements caused by the movement of this liquid mass thus accelerate or slow down the rotation of the planet. However, these long-known fluctuations could be quantified extremely precisely thanks to a new device from the Wettzell Geodetic Observatory (Technical University of Munich). It is a ring-shaped laser system whose algorithm has been corrected to allow greater measurement accuracy.
The rotation speed of the Earth with an accuracy of 9 decimal places
In a hermetic housing equipped with mirrors, two laser beams are generated, one propagating clockwise and 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 cause a tiny movement of the mirrors: one of the laser beams will have to travel a greater distance 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 fluctuations in rotational speed with an accuracy of 9 decimal places! The results were published in the journal Nature Photonics.
Originally posted 2023-11-14 07:52:19.