Fun fact: In December 2004, space telescopes detected something that briefly left them baffled: a gamma-ray flare so bright that, for a fraction of a second, it saturated the sensors of several satellites designed to watch the sky. The source was SGR 1806−20, a magnetar — a neutron star with the most powerful magnetic field known in the universe — located about 50,000 light-years away, on the other side of the galaxy. What’s most astonishing isn’t just that it was the brightest gamma-ray flare ever recorded, outshining even the most violent solar flares, but that its energy traveled that entire distance and still hit Earth hard enough to disturb the…