How the Earth turns: new Research Unit to measure the tiniest fluctuations

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The Earth continuously rotates on its axis like a giant spinning top. This rotation is not constant, however, but is influenced by factors such as high-pressure areas in the atmosphere, the shifting of water masses by the tides, and even the melting of ice sheets at the poles. It is precisely these fluctuations that are the focus of the new Research Unit “RING: Rotations in Physics, Geophysics, and Geodesy,” which has been awarded four million euros in funding by the German Research Foundation (DFG). “Precise measurements of the Earth’s rotation are indispensable not only for researching climate change, but also for functioning navigation devices,” explains Heiner Igel, Professor of Geophysics and Seismology at LMU and spokesperson for the new Research Unit.

The researchers are using ring lasers to visualize shifts in the Earth’s rotation that were scarcely measurable before. These optical measuring instruments record rotational motions via the so-called Sagnac effect, in which laser beams traveling the same closed path in opposite directions exhibit a frequency difference that is directly proportional to the rotation rate.

Application in geodesy and geophysics

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Building on their many years of expertise with the technology, the researchers plan to further develop both large stationary ring lasers – such as the ROMY ring laser at Fürstenfeldbruck and the ring laser at the Geodetic Observatory Wettzell – and portable sensors. “Our goal is to develop extremely sensitive rotational measurements with a high degree of short- and long-term stability, which can be used in geodesy and geophysics alike,” says Igel. In this way, the researchers want to gain new insights into processes that influence the Earth’s rotation and enable more precise analyses of earthquakes and the resulting seismic waves. This will furnish a much better understanding of key processes in the Earth system – from changes in climate to seismic activities – and allow them to be monitored more precisely in the future. Furthermore, precise data on the Earth’s rotation are an important basis for navigation systems and satellite technology.

The new Research Unit is composed of six subprojects, four of which contain LMU researchers. In addition to LMU as the applicant, the University of Bonn and the Federal Agency for Cartography and Geodesy (BKG) are also part of the project. Further partners are the Technical University of Munich (TUM), GFZ Potsdam, KIT Karlsruhe, the University of Hamburg, the Hamburger Observatory, the University of Hannover, TU Berlin, and the Geodetic Observatory Wettzell. DFG Research Units enable scientists to pursue pressing questions in their areas of research and forge innovative paths in their work. They are funded for a period of up to eight years.