All About Space

Do gravitatio­nal waves travel at the speed of light?

- Dr Kathleen E. Saavik Ford is an astrophysi­cist at City University of New York Graduate Centre, the Borough of Manhattan Community College and the American Museum of Natural History

Gravitatio­nal waves should travel at the speed of light, but in science we can never truly say that two things are exactly the same. We can only compare our measuremen­ts and say how much room they have to possibly be different. In the case of light and gravitatio­nal waves, you want to have an event that gives off both at the same instant, and then measure when both signals arrive. If a light wave and a gravitatio­nal wave were to race to us from Proxima Centauri, the nearest star after the Sun – a distance of a little more than four light years away – they would arrive at the finish line within a few nanosecond­s of each other. Perhaps even closer, but that’s as good as our measuremen­ts have gotten up to now.

We think that gravitatio­nal waves should travel at the speed of light because that is what Einstein’s theory of general relativity predicts. But Einstein may not be the final word on gravity – just as Newton’s ideas on gravity had to be modified by Einstein. That’s why we make measuremen­ts, to find out all the cool stuff our theories can’t yet explain!

 ??  ?? Left: The first gravitatio­nal wave detection occurred in 2015
Left: The first gravitatio­nal wave detection occurred in 2015
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