WEDNESDAY, 18 OCTOBER 2017
In general relativity, spacetime is treated as a geometric surface. This surface is capable of warping and bending, and gravity can be thought of as the result of curvature which alters trajectories. Gravitational waves are distortions in this surface that propagate as a wave and transport energy as gravitational radiation.
The possibility that waves of gravitational radiation might exist has been around since 1893, when the English physicist Heaviside compared the physics of gravity with that of electromagnetism. In 1905, after the formulation of special relativity, French physicist Poincaré suggested that gravitational waves should be required in a relativistic treatment of gravity. In 1916, Einstein predicted the existence of gravitational waves as a consequence of his theory of general relativity. It was not until 2016 that they were proven to exist, as the LIGO (Laser Interferometer Gravitational Wave Observatory) detected the waves emitted by the collision of a pair of black holes 1.3 billion light years away. In 2017, the LIGO team were awarded the Nobel Prize in Physics for this discovery.
"LIGO (Laser Interferometer Gravitational Wave Observatory) detected the waves emitted by the collision of a pair of black holes 1.3 billion light years away"
It is rare that an entirely new branch of physics opens up, but with the discovery of gravitational waves, the era of gravitational wave astronomy has begun. These observations could contribute to many areas of astrophysics and cosmology; for example, they could be used to learn more about the structures of neutron stars and the collisions of black holes. Some theorists are hoping to use them to learn more about the early universe, hoping that in the future they might even be able to detect the waves emitted during the first moments after the big bang when the universe was first created. They could also be used to tell us about how gravity itself works. In general relativity, gravitational waves would be expected to propagate at the speed of light. However, various modifications to general relativity have been proposed as solutions to some of the big open questions in cosmology, such as the dark energy problem, and these theories tend to predict that the waves will propagate at a different speed and have their amplitudes damped at different rates.
The first ever detection of gravitational waves at the LIGO was a big step forward for physics, but it was just the beginning of the new era of gravitational wave astronomy. The Nobel Prize was awarded for the discovery of gravitational waves; who knows how many more may be awarded for discoveries made through them.
Image Credit: NASA Goddard Photo and Video