GEO 600 is a
gravitational waveIn physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from the source. Predicted by Einstein's theory of general relativity, the waves transport energy known as gravitational radiation...
detector located near
SarstedtSarstedt is a town in the district of Hildesheim, Lower Saxony, Germany. It has around 17,800 inhabitants. Sarstedt is close to Hanover.The GEO 600 gravitational wave detector is located nearby....
, Germany. This instrument, and its sister interferometric detectors, when operational, are by far one of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of 10
-21, about the size of a single atom compared to the distance from the Sun to the Earth. GEO 600 is capable of detecting gravitational waves in the frequency range 50
HzThe hertz is a unit of frequency. It is defined as the number of complete cycles per second. It is the basic unit of frequency in the International System of Units , and is used worldwide in both general-purpose and scientific contexts...
- 1.5 kHz. Construction on the project began in 1995.
Joint science run with LIGO
In November 2005, it was announced that the
LIGOLIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, is a large physics experiment which is attempting to directly detect gravitational waves. Cofounded in 1992 by Kip Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT, LIGO is a joint project between scientists at...
and GEO instruments have begun an extended joint
science run. The three instruments (LIGO's instruments are located near
LivingstonLivingston is a town in and the parish seat of Livingston Parish, Louisiana, United States. The population was 1,342 at the 2000 census. It is part of the Baton Rouge Metropolitan Statistical Area....
, Louisiana and on the
Hanford SiteThe Hanford Site is a mostly decommissioned nuclear production complex on the Columbia River in the U.S. state of Washington, operated by the United States federal government. The site has been known by many names, including Hanford Works, Hanford Engineer Works, Hanford Nuclear Reservation or HNR,...
, Washington in the U.S.) will collect data for more than a year, with breaks for tuning and updates. This will be the fifth science run of GEO 600. No signals were detected on previous runs, but the sensitivity of the instruments (and the quality of the data analysis) is continually improving, and once the data from the current run are analyzed, it is hoped that they will reveal perhaps the arrival at Earth of perhaps two unambiguous bursts of gravitational waves. This would constitute the first direct detection of gravitational radiation.
Claimed link between GEO 600 detector noise and holographic properties of spacetimeThe holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region — preferably a light-like boundary like a gravitational horizon...
On January 15, 2009, it was reported in
New ScientistNew Scientist is a weekly international science magazine and website covering recent developments in science and technology for a general English-speaking audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of Reed Elsevier. New Scientist has maintained a...
that some yet unidentified noise that was present in the GEO 600 detector measurements might be because the instrument is sensitive to extremely small quantum fluctuations of space-time affecting the positions of parts of the detector. This claim was made by Craig Hogan, a scientist from
FermilabFermi National Accelerator Laboratory , located in Batavia near Chicago, Illinois, is a U.S. Department of Energy national laboratory specializing in high-energy particle physics. As of January 1, 2007, Fermilab is operated by the Fermi Research Alliance, a joint venture of the University of...
, on the basis of his own theory of how such fluctuations should occur motivated by the
holographic principleThe holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region — preferably a light-like boundary like a gravitational horizon...
.
The New Scientist story states that Hogan sent his prediction of "holographic noise" to the GEO 600 collaboration in June 2008, and subsequently received a plot of the excess noise which "looked exactly the same as my prediction". However, Hogan knew before that time that the experiment was finding excess noise. Hogan's article published in
Physical Review D in May 2008 states: "The approximate agreement of predicted holographic noise with otherwise unexplained noise in GEO 600 motivates further study." Hogan cites a 2007 talk from the GEO 600 collaboration which already mentions "mid-band 'mystery' noise", and where the noise spectra are plotted. A similar remark was made ("In the region between 100 Hz and 500 Hz a discrepancy between the uncorrelated sum of all noise projections and the actual observed sensitivity is found.") in a GEO 600 paper submitted in October 2007 and published in May 2008.
It is also a very common occurrence for gravitational wave detectors to find excess noise that is subsequently eliminated. According to Karsten Danzmann, the GEO 600 principal investigator, "The daily business of improving the sensitivity of these experiments always throws up some excess noise (...). We work to identify its cause, get rid of it and tackle the next source of excess noise." Additionally, some new estimates of the level of holographic noise in interferometry show that it must be much smaller in magnitude then it was claimed by Hogan.
See also
- See Gravitational radiation to learn more about gravitational radiation.
- LIGO
LIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, is a large physics experiment which is attempting to directly detect gravitational waves. Cofounded in 1992 by Kip Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT, LIGO is a joint project between scientists at...
, for the two American gravitational interferometric detectors.
- LISA
The Laser Interferometer Space Antenna experiment is a joint venture of the European Space Agency and NASA to detect and observe in detail gravitational waves from astronomical sources. In 2008 ESA reported LISA was in the mission formulation stage with the earliest possible launch taking place...
, for the space-based American gravitational interferometric detectors
- VIRGO
Virgo may refer to:* Virgo , an astrological sign* Virgo , a musical project between Andre Matos and Sascha Paeth* Virgo , a constellation* Beata Maria Virgo, latin title for Blessed Virgin Mary....
, for a competing European gravitational interferometric detector.
- TAMA 300
TAMA 300 is a gravitational wave detector located at the Mitaka campus of the National Astronomical Observatory of Japan. It is a project of the gravitational wave studies group at the Institute for Cosmic Ray Research of the University of Tokyo...
, for a Japanese gravitational interferometric detector.
- Einstein@Home
Einstein@Home is a distributed computing project hosted by the University of Wisconsin–Milwaukee and running on the Berkeley Open Infrastructure for Network Computing software platform...
, for a volunteer distributed computing program one can download in order to help the LIGO/GEO teams analyze their data
External links
- GEO 600 home page, the official website of the GEO 600 project.
- Cardiff Gravity Group, a page describing research at Cardiff University
Cardiff University is a leading university located in the Cathays Park area of Cardiff, Wales, United Kingdom. It received its Royal charter in 1883 and is a member of the Russell Group of Universities. The university is consistently recognised as providing the best university education in Wales...
in WalesWales is a country that is part of the United Kingdom, bordered by England to its east, and the Atlantic Ocean and Irish Sea to its west. It is also an elective region of the European Union...
, including collaboration in the GEO 600 project, includes an excellent list of tutorials on gravitational wave radiation.
- Amos, Jonathan. Science to ride gravitational waves. November 8, 2005. BBC News.