The Enormous Motion Sensor that Tells the Motion of Our Planet from a Bunker in Germany

An enormous underground motion sensor located in Germany has just taken its initial measurements of the spin and tilt of our planet. Scientists are now getting the accuracy of the machine up to date, but their observations could still maintain GPS navigation at a working standard on some devices, such as smartphones.

The Rotation Is Not Always the Same

The rotation of the Earth is constantly put off-track by natural phenomena such as ocean tides and earthquakes, thus needing regular correction of the GPS satellite signal. Normally, the corrections use telescope observations, offering a set of celestial coordinates to figure out the orientation of our planet  within space.

Why We Need a Motion Sensor

Unfortunately, data found in telescopes is difficult to process, sometimes taking multiple days.  The little wobbles within Earth can be monitored by the Rotational Motions in Seismology, also known as the ROMY gyroscope array. This was proved by scientists in a recent experiment that they have published on 17 July in the academic journal Physical Review.

How It Works

Basically, The Rotational Motions in Seismology is an upside-down pyramid composed out of pipes. The ROMY is around the length of a telephone pole on each of its sides. It has four triangular faces and they all measure motion in different directions. On every single side, there is a laser beam that runs clockwise through the triangle-shaped piping, all while another runs counterclockwise. The triangles go in tandem with the rotation of our planet and laser beams go in the same direction as the motion, but travel longer distances because they need to loop around the triangle.

Simultaneously, beams going in the other direction have their very wavelength compressed because their path is a lot shorter. At the end, there is a certain mismatch between the wavelength of the beams. Processing the differences between these wavelengths is how the researchers at the Rotational Motions in Seismology find out the tilt and speed of the planet’s rotation.

Melanie J. Gullett
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