Illustration of the double pulsar PSR J0737−3039A/B. (Michael Kramer/MPIfRA) Two pulsars locked in close binary orbit have once again validated predictions made by Einstein's theory of general relativity. Over 16 years, an international team of astronomers has observed the pulsar pair, named PSR J0737−3039A/B, finding that the relativistic effects can be measured in the timing of their pulses – just as predicted and expected. This is the first time these effects have been observed. "We studied a system of compact stars that is an unrivalled laboratory to test gravity theories in the presence of very strong gravitational fields," says astronomer...