European laser interferometer puts theory of relativity to the test
The VIRGO laser interferometer, a Franco-Italian instrument, has started scientific operations. This powerful piece of scientific infrastructure is expected to enable scientists to put to the test Albert Einstein's theory on the existence of gravitational waves. Located in Pisa, Italy, VIRGO is said to be one of Europe's largest scientific infrastructures, consisting of two perpendicular arms, each three kilometres long. Multiple reflections between a series of high quality mirrors extend the optical length of each arm to 120 kilometres, enabling the detector to pick up a gravitational signal. The project is co-funded by French National Scientific Research Centre (CNRS) and the Italian Institute for Nuclear Physics (INFN). In Einstein's theory of relativity, gravitational waves are described as ripples in the curvature of space-time generated by violent cosmic events like the explosion of a supernova, or the fusion of a couple of stars or black holes. However, due to the waves' weak amplitude, experts have been unable to successfully intercept and measure them. Thanks to its frequency range, which extends from 10 to 6,000 Hz, the VIRGO laser instrument is able to pick up even the weakest gravitational waves. To reach the extreme sensitivity required for this detection and to avoid seismic noise, each optical component is isolated from ground motions at a height of 10 metres. Furthermore, as the presence of a residual gas would affect the measurements, scientists have developed large ultra high vacuum vessels in which the light beam can travel undisturbed. VIRGO will operate day and night, continuously listening out for gravitational waves coming from the near Universe (as far out as the Virgo galaxy cluster). When signals are detected, they will be recorded and undergo a preliminary analysis with the help of an online computer system. This data will then be made available to the scientific community for more thorough study. The VIRGO teams have linked up with scientists at LIGO (Laser Interferometer Gravitational-wave Observatory) in the US, and GEO (German-UK Gravitation Wave Detector), joining forces in the hunt for gravitational waves. Pooling data is expected to increase the chances of detecting the first gravitational waves, and will provide more information about the location of the source. Joint analysis of the data will then take place.
Countries
France, Italy