GEO 600
Encyclopedia
GEO 600 is a gravitational wave
detector located near Sarstedt
, Germany. This instrument, and its sister interferometric detectors, when operational, are some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of one part in 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 Hz
to 1.5 kHz. Construction on the project began in 1995.
and GEO instruments have begun an extended joint science run. The three instruments (LIGO's instruments are located near Livingston
, Louisiana and on the Hanford Site
, 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 perhaps reveal the arrival at Earth of two unambiguous bursts of gravitational waves. This would constitute the first direct detection of gravitational radiation.
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 Fermilab
, on the basis of his own theory of how such fluctuations should occur motivated by the holographic principle
.
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 than was claimed by Hogan.
Gravitational wave
In physics, gravitational waves are theoretical ripples in the curvature of spacetime which propagates as a wave, traveling outward from the source. Predicted to exist by Albert Einstein in 1916 on the basis of his theory of general relativity, gravitational waves theoretically transport energy as...
detector located near Sarstedt
Sarstedt
Sarstedt 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 some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of one part in 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 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
to 1.5 kHz. Construction on the project began in 1995.
Joint science run with LIGO
In November 2005, it was announced that the LIGOLIGO
LIGO, which stands for the Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming 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 MIT,...
and GEO instruments have begun an extended joint science run. The three instruments (LIGO's instruments are located near Livingston
Livingston, Louisiana
Livingston 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 Site
Hanford Site
The 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 or HEW, Hanford Nuclear Reservation...
, 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 perhaps reveal the arrival at Earth of 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 spacetime
On January 15, 2009, it was reported in New ScientistNew Scientist
New Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
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
Craig Hogan
Craig Hogan is a Professor of Astronomy and Physics at the University of Chicago and he is the director of the Fermilab Center for Particle Astrophysics....
, a scientist from Fermilab
Fermilab
Fermi National Accelerator Laboratory , located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics...
, on the basis of his own theory of how such fluctuations should occur motivated by the holographic principle
Holographic principle
The 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 than was claimed by Hogan.
See also
- Gravitational radiation
- Fermilab Holometer
- LIGOLIGOLIGO, which stands for the Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming 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 MIT,...
, for the two American gravitational interferometric detectors. - LISALaser Interferometer Space AntennaThe Laser Interferometer Space Antenna is a planned space mission to detect and accurately measure gravitational waves from astronomical sources. LISA was originally conceived as a joint effort between the United States space agency NASA and the European Space Agency...
, for the space-based ESA, NASA gravitational wave detector - VIRGOVirgo-Astronomy:* Virgo Cluster, a cluster of galaxies in the constellation Virgo* Virgo , a constellation* Virgo Stellar Stream, remains of a dwarf galaxy* Virgo Supercluster, a galactic supercluster-Surname:* Virgo...
, for the European gravitational interferometric detector. - TAMA 300TAMA 300TAMA 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@HomeEinstein@HomeEinstein@Home is a volunteer distributed computing project hosted by the University of Wisconsin–Milwaukee and the Max Planck Institute for Gravitational Physics . The project is directed by Bruce Allen...
, 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 UniversityCardiff UniversityCardiff University is a leading research 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 high quality research-based...
in WalesWalesWales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, 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.