Can light itself cast a shadow? It may sound like a philosophical riddle, but researchers have found that under certain conditions, a laser beam can act like an opaque object and cast a shadow. The discovery challenges the traditional understanding of shadows and opens new possibilities for technologies that could use a laser beam to control another laser beam.

To ask if a beam of light can make a shadow sounds like a sort of Zen paradox, but physicists have demonstrated the possibility. They used a laser beam to block another laser beam, albeit with some crystalline assistance.

It turns out that if you manipulate a laser just right, then hit it side-on with another light source, it’s possible to create this bizarre optical effect. Shadows are so familiar in everyday life that it feels a little weird having to define them ...

Light shines; photons travel until they hit an object through which they cannot pass; this blockage creates a shadow, a little piece of darkness where the light has been impeded. Physicists, however,