When massive objects such as black holes merge or neutron stars collide, they can send gravitational waves rippling through the universe. These waves travel at the speed of light and cause extremely small distortions in space-time. Albert Einstein predicted their existence more than a century ago, but scientists did not directly observe them until 2015. Now, Prof. Ralf Schützhold, a theoretical physicist at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), has proposed taking the science further. He has outlined an experiment that would not only detect gravitational waves but also actively influence them. The concept, published in the journal Physical Review Letters, could also help scientists explore the long-suspected quantum nature of gravity.
"Gravity affects everything, including light," says Schützhold. This means that when light waves encounter gravitational waves, the two can interact. His proposal focuses on shifting tiny amounts of energy from a beam of light into a passing gravitational wave. As this happens, the light loses a small amount of energy, while the gravitational wave gains exactly the same amount. That energy corresponds to one or more gravitons, the theoretical particles believed to carry the force of gravity, although they have never been directly observed. "It would make the gravitational wave a tiny bit more intensive," explains the physicist. At the same time, the light wave experiences a barely detectable change in its frequency.
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