Brussels, 25 Jul 2003

Scientists from the French national research centre (CNRS) and the Italian institute for nuclear physics have completed work on an EU funded laser interferometer, a powerful scientific instrument which will enable them to put Albert Einstein's prediction of the existence of gravitational waves to the test.

The measurement instrument was unveiled during a ceremony involving Claudie Haigner¨¦, French Minister for Research and New Technologies, and Letizia Moratti, Italy's Minister for Education, Universities and Research on 23 July in Pisa, Italy.

Funded under the training and mobility of researchers (TMR) programme of the Fourth Framework Programme (FP4), the 78 million euro VIRGO interferometer is said to be one of Europe's largest scientific tools, consisting of two 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.

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 weak amplitude of the waves, experts have been unable to successfully intercept and measure them.

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Now, due to its frequency range, which extends from 10 to 6,000 Hz, the VIRGO laser instrument is well equipped to pick up 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 ten metres. Furthermore, as the presence of a residual gas would affect the measurements, scientists have also developed large ultra high vacuum vessels in which the light beam can travel undisturbed.

Virgo will run day and night, listening to even the faintest gravitational signals, which may arrive at any time and come from any part of the Universe. The signals will be detected, recorded and pre-analysed by an online computing system. This data will then be made available to the scientific community for further analysis.

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