The universe is expanding at an accelerated rate and this expansion is an effect of dark energy. We don’t know what dark energy is and there are different explanations for it, but scientists suspect they can rule out some of the models by using gravitational waves.
Dr Lucas Lombriser and Dr Nelson Lima from the University of Edinburgh have looked at Einstein’s theory of general relativity and alternatives of it known as modified gravity. According to their studies, published in Physics Letters B, it may be possible to tell which model is correct by accurately measuring the speed of gravity.
Now, gravity is believed to be moving at the speed of light. Indirect measurements from galactic observations and direct measurements of gravitational waves seem to confirm this. The uncertainty on this measurement is tiny, but every new detection from the Laser Interferometer Gravitational-Wave Observatory (LIGO) will help refine this value.
If the value is found to be different from the speed of light, it would mean that our current understanding of the universe is not correct and we might need a different theory of gravity.
"Recent direct gravitational wave detection has opened up a new observational window to our Universe,” Dr Lombriser said in a statement. “Our results give an impression of how this will guide us in solving one of the most fundamental problems in physics."
According to the leading theory, known as the standard cosmological model, the universe is dominated by dark matter and dark energy, which is described by Einstein's relativity.. This is not just speculation. The standard model matches the observations incredibly well, but despite decade-long studies, we still don’t know what dark matter and dark energy is.
For this reason, several other scientists are investigating alternative ideas. These ideas are built purposely to avoid dark energy and dark matter, but they have not had the same success as the standard model in explaining the observations.
LIGO has recently undergone an upgrade and is currently scanning the skies for hints of gravitational waves. Hopefully, many more detections will be added to last year's, and if these researchers are correct, LIGO might deliver a crucial clue about the true nature of the universe.