Imagine shining a flashlight across a dark room. You can predict exactly what the light will do: travel in a straight line from one point to another. That seems obvious because, in the world we see around us, light appears to follow a single, clear path.

Quantum mechanics paints a far stranger picture.

If you zoom in to the atomic scale, light does not behave as though it follows only one straight route. Instead, a particle of light explores every path available to it at once. One path may indeed be the straight line across the room. But others could involve the light bouncing off walls, curving through space or tracing wildly improbable detours before reaching its destination.