A flashlight beam travels straight into the dark: that's how we usually think of light. But near a massive body, like a star or a black hole, space is curved, and the beam bends smoothly, as if guided by an invisible hand. The authors of a new study have worked out exactly how gravity alters the familiar laws of electricity and magnetism. They took Maxwell's equations (the very ones that describe light, radio waves, and the behavior of charges) and rewrote them for the curved space around a black hole.

They considered two types of observers. The first hovers in place, resisting the pull. For them, the equations look almost familiar, with only corrections: distances and time stretch, and space itself acts like a lens, altering the field strength. The second observer falls freely into the black hole. In their world, electric and magnetic fields mix like paints in flowing water. A stationary charge appears to them as a flowing current, and the equations link what was once separate. Meanwhile, in the transverse directions, along the angles, everything remains as before. Thus, gravity reshapes the very fabric of electromagnetism. And the flashlight beam we started with, near a black hole, no longer just bends: it follows new rules, where electricity and magnetism are woven together.