The VIRGO project is a physics experiment; its aim is the detection of gravitational waves. ... It has not yet been possible to detect directly the gravitational waves: it remains one of the major challenges of experimental physics. ... Interferometric antennas for gravitational waves Gravitational waves distort space-time: along two perpendicular directions, the distances between fixed points will increase (resp. decrease), at the arrival of a gravitational wave. ... Publications from our Group . ...

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The leaning tower of Pisa . ... The velocity of a ball dropped from a high place increases each second by a constant amount, usually denoted by the small letter g (for gravity). ... For the falling ball in the preceding example, after t seconds that would be . ... If in addition the ball is also given at the start a horizontal velocity w , its horizontal motion continues unimpeded, advancing a distance w each second, even while the ball is falling (air resistance is now ignored). ...

... The Arecibo 430 MHz radar uses incoherent scatter to determine the characteristics of the ionosphere. It is part of a chain of incoherent scatter radars operated by the Upper Atmospheric Facilities program of the National Science Foundation with strong links to the CEDAR program and the National Space Weather program. ... The Arecibo radar is extremely powerful and sensitive; it is capable of making very accurate measurements of many ionospheric parameters. ...