The sound of colliding black holes - and how to filter out the noise of the Universe from it

Meeting of experts at the AEI from 6 to 9 July, 2009

June 25, 2009

Detection of gravitational waves
The direct proof of the gravitational waves predicted by Albert Einstein - tiny distortions of space-time - remains one of the most important open questions of modern science. Their direct observation will lead to an era of gravitational wave astronomy and provide completely new insights into our universe. With the help of gravitational waves, it will be possible to look back into the first billionth of a second of the universe and thereby solve many riddles about its origins. Observation methods that have been used up to now have been unable to achieve these insights.

The detection of gravitational waves would have far-reaching effects in addition to further substantiation of the general theory of relativity. For the first time, it will be possible to take a look back into the "nursery" of the universe. Up to now observation of the sky has been restricted to the electromagnetic spectrum (for example, radio and X-ray telescopes, as well as the observation of visible light). The information that is available to us about the origin of the universe only goes back to 380,000 years after the Big Bang. Observations earlier than that are not now possible, since the universe only became transparent to electromagnetic radiation at that time. The various theories on the earlier universe have therefore remained experimentally unconfirmed. The direct measurement of gravitational waves would open up completely new possibilities in this regard, since it would presumably be possible to listen back to the first billionth of the first second that followed the Big Bang. With the help of gravitational wave astronomy, completely new fields of science would be opened up.

Status of currently operational gravitational wave observatories
A number of first-generation gravitational wave detectors are currently operating in Europe: German-British GEO600 observatory is operated by the AEI in the vicinity of Hannover and funded by STFC1, MPG2, as well as the state of Lower Saxony, while the French-Italian-Dutch Virgo project is located in Cascina in the vicinity of Pisa. The data from these measuring devices are combined with those of the three American LIGO interferometers. The entire data pool is currently being used to look for gravitational wave signals from astrophysical sources.

During the course of the next decade, all interferometric gravitational wave detectors will be upgraded to second-generation instruments. The sensitivity of Virgo and LIGO in lower frequencies (up to about one kilohertz) will be increased tenfold using technologies developed in Europe. In particular, GEO600 will do pioneering work in the field of broadband observation of high frequencies, here too through the development and use of new technologies. GEO600 is regarded as the think tank of gravitational wave research.

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