Magnetar may offer first direct proof of quantum vacuum predicted by Heisenberg 90 years ago

The colossal magnetic field of a magnetar may have revealed vacuum birefringence — a quantum effect predicted by Werner Heisenberg nearly 90 years ago, in which seemingly empty space alters the behaviour of light. If confirmed, it would be the first direct evidence that the quantum vacuum is not truly empty. The finding could open a new window into the strange physics of empty space.