The Mudcat Café TM
Thread #59418   Message #1455809
Posted By: Amos
08-Apr-05 - 08:15 PM
Thread Name: BS: The Mother of all BS threads
Subject: RE: BS: The Mother of all BS threads
The VIRGO gravitational-wave detector will be officially opened at Cascina, near Pisa, in Italy today. The detector - which will search for the gravitational waves predicted by the general theory of relativity - is a joint project between the INFN in Italy and the CNRS in France. The European Gravitational Observatory will manage the facility.

Gravitational waves are ripples in the fabric of space-time that are produced when massive bodies accelerate through space. However, the waves are very weak - even for the strongest astrophysical sources, such as supernova explosions or collisions between neutron stars and black holes – and therefore extremely difficult to detect.

When a gravitational wave reaches the Earth it should expand space in one direction and contract it in the perpendicular direction. VIRGO relies on laser interferometers to detect the effect of these changes on pairs of widely separated test masses. The arms of the interferometer are 3 kilometres long and they are at right angles to each other (see figure). Changes in the interference pattern produced by two laser beams reflected off mirrors on the test masses will reflect changes in the length of the arms.

However, the changes caused by any gravitational wave will be extremely small - only about 10-21m - so the detector must be very sensitive. In particular, it must be seismically isolated from its environment, and it must use an ultrahigh vacuum cavity and the best possible mirrors and other optical components.

Virgo has passed preliminary tests and will begin to record data in a few months. It will join a global network of gravitational-wave detectors that already includes the two LIGO detectors (which are both 4 km long) in the US, GEO600 in Germany (600 m) and TAMA in Japan (300 m).

Grave business indeed, that only the best of good heads may comprehend!! Of all the kinds of folk I know, only the fairest maidens have such heads, nor are free enough of gravity to dance around so massive a subject.

And, if we are to avoid unfairness, we must constrain the set to only maidens who are fair, and can dance, and speak well, too -- which is a scarcer set now than once it was.