As they spin, two pulsars (blue circles) emit beams of radiation (yellow), channeled by strong magnetic fields (light blue doughnuts). When the beams sweep past Earth, they appear as metronome-like repeating blips. The two pulsars revealed the effects of the warping of spacetime (represented by the grid, bottom) caused by the pulsars, testing Einstein’s general theory of relativity.
© Michael Kramer/MPIfR