Media release

From: Springer Nature

A laser gyroscope that can detect minute changes in the length of a day, accurate to a few milliseconds, resulting from changes in the Earth’s rotation, is described in an article published in Nature Photonics.

The duration of a day on Earth is not constant. The Earth’s rotation is influenced by the combined attraction of the Sun and the Moon, as well as by oceanic currents and wind circulation patterns that result in small changes in the Earth’s orientation in space. Traditionally, measuring these effects involves complex techniques using data from radio telescopes scattered across the globe or signals transmitted by multiple Earth-orbiting satellites.

Ulrich Schreiber and colleagues employ a laser gyroscope that enables the tracking of changes in the length of a day. The gyroscope consists of a 16-metre-long laser cavity where two laser beams travel in opposing directions. The interaction of these beams produces distinctive interference patterns, a phenomenon typical of laser beams. As the Earth rotates and fluctuates in space, so does the apparatus, which results in the distance covered by light in opposite directions inside the cavity becoming unequal and affecting the interference pattern. By monitoring interference over time, the authors were able to measure variations in the length of the day every three hours accurate to a few milliseconds over four months. This is in contrast to existing techniques that only provide a single measurement per day.

The authors suggest their findings offer an alternative method for measuring subtle variations in day length. The findings may aid our understanding and inform geophysical models of global transport phenomena.