WHAT: GEO 600 laser interferometer
WHERE: Hannover, Germany
WHY: To measure gravitational waves predicted by Einstein's general theory of relativity but yet to be observed. These waves - space-time ripples caused by the movement of large cosmic masses like black holes and compact binary stars - will help determine distances across the universe. This data will be critical in fixing the Hubble constant, a number long sought in cosmology and key to gauging the universe's rate of expansion.
WHO: University of Hannover, University of Glasgow, Max Planck Institute, Cardiff University, Albert Einstein Institute
HOW: A neodymium-doped yttrium aluminum garnet laser beam, fired from the corner station, bounces back and forth twice along each stainless steel arm of the L-shaped facility. Because the arms are identical - tubes 600 meters in length and 60 cm in diameter - the beams should traverse both in exactly the same amount of time. Any variations (measured by a photodetector) indicate that the tubes' length was temporarily altered by a gravitational wave. The GEO 600 is due to start test operations sometime this summer. Results will be correlated with data from partner sites in the US, Italy, and Japan, helping identify the precise celestial sources of gravitational waves.
