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Physics

'Dark photon' theory of light aims to tear up a century of physics

One of the most famous findings in physics could be wrong – the double-slit experiment was long thought to confirm that light can be a wave, but its results can be fully explained using only quantum particles

By Karmela Padavic-Callaghan

29 April 2025

In the double-slit experiment, light waves interfere with each other – or do they?

RUSSELL KIGHTLEY/SCIENCE PHOTO LIBRARY

Light is both a wave and a particle – or so we have thought for about a hundred years. Since the advent of quantum physics, light has been understood to exhibit wave-particle duality. One part of this duality can be traced to physicist Thomas Young who, in 1801, performed an experiment that confirmed light’s wave character: the double-slit experiment. But a radical new interpretation brings into question the results of this famous experiment, and indeed, the very nature of light itself.

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