I, for one, would like to be in on the detection of gravitational waves. They flow naturally from the theory of General Relativity and ought to be out there, but none have ever been directly detected. What might make finding them easier would be a spectacular event, such as the merger of a pulsar and a neutron star or a black hole, an event that should cause a huge emission of gamma rays in its final moments. Short-period binaries are the ticket — find them and you have the chance to test General Relativity to high degrees of precision.
Some 200,000 volunteers have already signed up for the EINSTEIN@Home project, which searches for gravitational waves from rapidly spinning neutron stars. The project is now looking for volunteers for its new search, one that will use home computers to analyze data gathered at the Arecibo Observatory in Puerto Rico in the hunt for binary radio pulsars.
This is jazzy stuff, another opportunity, like SETI@Home and the Galaxy Zoo, for those of us with an astronomical bent to deploy our computing cycles productively. And what could be more exotic? Gravitational wave detection takes us into fundamental questions about the physics of gravity and may offer new tools for astronomical observations. Think of these waves as ripples in spacetime emitted by accelerating masses, an analog to the way accelerating charges produce electromagnetic waves.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) offers four concrete goals that could be the result of current investigations:
- Verify directly General Relativity’s prediction that gravitational waves exist.
- Test General Relativity’s prediction that these waves propagate at the same speed as light, and that the graviton (the fundamental particle that accompanies these waves) has zero rest mass.
- Test General Relativity’s prediction that the forces the waves exert on matter are perpendicular to the waves’ direction of travel, and stretch matter along one perpendicular direction while squeezing it along the other; and also, thereby, test General Relativity’s prediction that the graviton has twice the rate of spin as the photon.
- Firmly verify that black holes exist, and test General Relativity’s predictions for the violently pulsating space-time curvature accompanying the collision of two black holes. This will be the most stringent test ever of Einstein’s General Relativity theory.
We’ve come to realize how effective distributed computing can be. A Cornell University news release points out that current searches of radio data are ineffective for pulsars in binary systems with orbital periods less than fifty minutes. The EINSTEIN@Home project will put enough computational power onto the job that we can begin to detect systems with much shorter periods, down to a brief eleven minutes. We’ll wind up with better estimates of binary system formation and disappearance in such scenarios, along with precisely identified targets for gravitational wave detectors.
From a propulsion standpoint, what intrigues us is that a deeper understanding of gravity and its coupling with electromagnetism could point to a theoretical basis for manipulating inertia or gravity itself. Mass, after all, warps the spacetime against which electromagnetism is measured. Now we’ve moved a long way from the original gravitational wave detection, and haven’t begun to get into the question of energy requirements that could render such thoughts chimerical, but finding gravitational waves takes us deeper into this force’s rich mysteries.