Better hearing with spaced-apart ears

June 2, 2011, Max-Planck-Gesellschaft
An ear into space: while researchers convert the other detectors to improve their sensitivity, the German-British GEO600 project in Ruthe near Hanover continues to listen out for gravitational waves. Credit: Albert-Einstein Institute Hannover

( -- Detectors in the US, Germany and Italy are lying in wait to gather evidence that would unveil one of Albert Einstein’s last secrets: gravitational waves. Up to now, it has not been possible to detect these ripples in the curvature of space-time directly. However, if the available detectors were to be distributed differently across the globe, the chance of detecting the gravitational waves would increase more than twofold. This is the conclusion reached in a new study by Bernard F. Schutz, Director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Golm. A further improvement in the detection process could also be achieved through the construction of additional gravitational wave observatories.

Many methods of studying the universe are available to us, most of which are based on the analysis of electromagnetic radiation from space. This involves the examination of photos from different eras, so to speak, which were taken on different wavelengths. Given that the traditional methods of space observation are blind to various phenomena, our perceptive spectrum would be extended considerably if we could also find a way of using our ears in this process.

provide information about star explosions, collisions between black holes and neutron stars, and even about the Big Bang. Their frequencies do not lie in the electromagnetic range but in the acoustic range. These dents in space-time move at the speed of light and make the universe resonate.

Researchers have already constructed “telescope ears” for the detection of gravitational waves in Germany (GEO600), at two locations in the United States (LIGO) and in Italy (Virgo). These gravitational wave detectors measure and evaluate data together in a network. The observatories in the US and Italy are now being upgraded to enable the direct detection of gravitational waves for the first time and will recommence operation from 2016, taking measurements of ten times greater sensitivity than it is possible to do at present.

Up to now, the scientists have assumed that they would be able to observe an average of 40 melting neutron stars or black holes annually. Bernard F. Schutz’s study now reveals that a total of 160 such events could in fact be observed per year. However, this cannot be achieved with the current spatial distribution of the detectors. What is needed is a measuring instrument on the other side of the world – an “ear” at the “back of the head”, as it were.

The measuring sensitivity of a detector network depends on the sensitivity of the individual detectors and their position on earth. In his study, Bernard F. Schutz demonstrates how this relationship can be characterised by three figures for any network: the distance from which the gravitational wave in the sky can be perceived by the individual detector; the minimum signal-to-noise ratio at which gravitational wave detection is possible; the geometric arrangement of the detectors in the network.

“The transfer of one of the existing LIGO instruments from the US to Australia alone would increase the detection rate by a factor of two to four and provide far more accurate information about the events observed,” says Schutz. If – as planned – gravitational wave detectors commence operation in Japan, Australia and India, the scientists will be able to observe around 370 astronomical events annually - a figure that should increase to 500 per year once operation has become routine. The benefits gained from the improvement in measurement accuracy will fully offset the necessary investment.

“A new gravitational wave detector in Japan, whose construction was decided on last year, would further increase the sensitivity and reliability of the detector network and, moreover, enable the observation of a larger proportion of the sky,” says Schutz. “Not only would we be more certain than ever before of being able to measure Einstein’s waves directly, we would also obtain completely new information about and gamma-ray bursts. This would mark the advent of a whole new type of astronomy.”

Explore further: Scientist instils new hope of detecting gravitational waves

More information: Bernard F. Schutz, Networks of gravitational wave detectors and three figures of merit, Classical and Quantum Gravity, 2011.

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not rated yet Jun 02, 2011
500 events a year? From what I have read and following this technology over the years, scientists have yet to detect the FIRST gravitational wave or ripple. If this new detection scheme fails as well, something is seriously amiss with the theories and things are not as they seem. I hope they succeed though.
4 / 5 (1) Jun 02, 2011
I'm totally unenthusiastic, I was in college at WSU when LIGO went active at Hanford. I even visited during the first upgrade during 2004. They've built an incredibly sophisticated and sensitive machine. The problem? They built it on earth. They didn't build a very good gravitational wave interferometer they built a very nice seismometer.

If you read their data-set transcriptions there are tons of false positives and other errors where they have to take it offline or recalibrate. They get hits all the time. What was it this time? It's a truck shaking the roadway, from 20 miles away that is carrying granite for new counter tops. Seriously!

Yeah it's sensitive, but biggest waste of money ever... the only way to get positive data is to build it in space or on the moon, where it's isolated from any human activity that shakes things.
not rated yet Jun 02, 2011
I sure these guys thought they would find them too.

The tantalizing Quest for Gravity Waves
Popular Science Apr 1981

not rated yet Jun 03, 2011
It's the Shapiros (take your pick) vs. Stephen J. Crothers' mathematics.

I went with the math years ago.
not rated yet Jun 03, 2011
They built it on earth. They didn't build a very good gravitational wave interferometer they built a very nice seismometer.

This makes me wonder what exactly it is doing in the countryside, instead of say.... The middle of the Sahara, or atop a Chilean mountain, or in Arizona. Telescopes aren't built where they will be subjected to unnecessary interference, why was this one?

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