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Huge underground lasers measure Earth’s spin with extreme precision

Lasers reflected by supermirrors sit at the bottom of a cavern in Munich

Jonas Igel

Deep inside a concrete-filled pit just outside Munich, researchers are taking some of the best measurements ever of Earth’s motion. They’re using huge, red lasers set 15 metres below Earth’s surface to get data that could help make GPS navigation more precise.

GPS navigation is based on measurements from satellites which have to be calibrated with measurements of Earth’s orientation in space – that is constantly changing. “If we don’t measure it, our GPS location that we have in our car and our phone …