Gravitational waves (GWs) are predicted by Einstein’s theory of general relativity. They are described as ripples in spacetime that propagate at the speed of light through space. They can apparently also be described as “graviton particles” that transfer gravitational energy, similar to photons that transfer electromagnetic energy.
Gravitational waves transfer energy quite differently to the way photons do. GWs are neither absorbed, nor reflected by matter, but pass straight through them, losing only a tiny amount of their energy. Also, while photons are emitted in legions just about everywhere in space, GW-emitting bodies are scarce, at least the ones that emit strong enough GWs to give us any hope of detection. As I understand it, GWs loose amplitude directly proportional to distance traveled, just like light waves.
GW detectors are huge (and very expensive) contraptions, mostly buried below the surface of Earth, e.g., the LIGO facility. LIGO stands for Laser Interferometer Gravitational-wave Observatory. In about 2 years of working at near-full sensitivity, LIGO has registered no GWs. Plans are now to build an even larger and more expensive GW detector in space, called LISA (Laser Interferometer Space Antenna).
GW’s have been detected indirectly as the ‘anomalous’ in-spiraling of two pulsars orbiting each other. The rate of in-spiral matches the predictions of general relativity almost precisely, which predicts that the “lost energy” is radiated away as gravitational waves. Scientist are fairly optimistic that GWs exist and that it is just a matter of having a sensitive enough detector and then wait for an event that radiates GWs and is close enough so that we can detect it.
My question: are GW detection attempts not a huge waste of resources, while there are other more pressing needs?