Detecting Elusive Gravity Waves From The Other End Of The Cosmos
May 18, 2013

Researchers Propose New Gravitational Wave Detector

John P. Millis, Ph.D. for — Your Universe Online

Exchange of electromagnetic energy is fairly well understood. The force carrier, the photon, is readily detectable and manipulated, making the physics of electromagnetic radiation easy to study.

By contrast, gravitational exchanges pose a much greater challenge. This arises, at least in part, because the gravitational force is so much weaker than that of electricity and magnetism. Also, the force carrier itself, the gravitational wave, has never been directly observed. Observations of a binary neutron star system provided the first indirect evidence of gravitational waves. The authors of that study, Russell A. Hulse and Joseph H. Taylor Jr., were honored with the 1993 Nobel Prize in Physics.

However, if sensitive enough detectors could be constructed, then scientists could begin constructing a gravitational map of the cosmos. Andrew Geraci, University of Nevada, Reno physics professor explains, "directly detecting gravitational waves from astrophysical sources enables a new type of astronomy, which can give us 'pictures' of the sky analogous to what we have by using telescopes. In this way the invention of a gravitational wave detector, which lets us 'see' the universe through gravity waves, is analogous to the invention of the telescope, which let us see the universe using light. Having such detectors will allow us to learn more about astrophysical objects in our universe, such as black holes."

But now, researchers are proposing a new type of instrument that would detect gravitational waves originating from the distant edges of the Universe.

As Geraci notes, "Gravitational waves represent one of the missing pieces of Einstein's theory of general relativity. While there is a global effort already out there to find gravitational waves, our proposed method is an alternate approach with greater sensitivity in a significantly smaller device. Our detector is complementary to existing gravitational wave detectors, in that it is more sensitive to sources in a higher frequency band, so we could see signals that other detectors might potentially miss."

This new device, designed by Geraci and colleague Asimina Arvanitaki at Stanford University, would set a small, laser-cooled, tunable sensor floating in the center of an optical cavity. Since the sensor would lack any friction inside the vessel, the system would operate with greater sensitivity than other experiments.

"Gravity waves propagate from the remote corners of our universe, they stretch and squeeze the fabric of space-time. A passing gravity wave changes the physically measured distance between two test masses - small discs or spheres. In our approach, such a mass experiences minimal friction and therefore is very sensitive to small forces," says Geraci.

If successful, the detector proposed by Geraci and Arvanitaki could surpass the sensitivity of the other gravitational wave observatories on the horizon, particularly in the search for signals in the 50 to 300 kilohertz band.

Their paper, "Detecting high-frequency gravitational waves with optically levitated sensors," has been published in Physical Review Letters, a publication of the physics organization American Physical Society.