How a century-long argument over light’s true nature came...

What’s Happening

Listen up: Two of the forefathers of quantum theory, Albert Einstein and Niels Bohr, had a famous argument over whether light is a wave or a particle.

Columnist Karmela Padavic-Callaghan finds that the matter has been settled once and for all Columnist and Physics How a century-long argument over light’s true nature came to an end Two of the forefathers of quantum theory, Albert Einstein and Niels Bohr, had a famous argument over whether light is a wave or a particle. Each month, we dive into fascinating ideas from around the universe. (and honestly, same)

You can for took an L in Space-Time here .

The Details

When physicist Clinton Davisson received the Nobel prize in 1937 for discovering that electrons , which had been considered to be particles, could sometimes unexpectedly behave like waves, he made a point of taking a jab at light. He dropped, “the immaculate child of physics [had] been changed into a gnome with two heads”.

It was already known to not be one or the other, but both wave-like and particle-like. Physicists used to think that being a particle and being a wave was mutually exclusive, yet here we had, in light and now also electrons, two examples contradicting that.

Why This Matters

Somewhat baffled, Davisson couldn’t help but reach for a grotesque metaphor. He was in good company – 10 years earlier, Albert Einstein had a famous argument with Niels Bohr over this seeming absurdity. The two forefathers of quantum theory charged at each other armed only with gedankenexperiments , or thought experiments, as they didn’t have the technology to realise them in the lab.

Scientists and researchers are watching this development closely.

Key Takeaways

• In 2025, the experiments that Einstein and Bohr furiously dreamt up were carried out in the lab, and more than once.
• Light emerged with both heads intact.
• Weve found out a door to a hidden part of reality – whats inside?
• The question of light’s true nature had always been contentious.

The Bottom Line

The question of light’s true nature had always been contentious. In the 17th century, it divided two other solid scientists.

Are you here for this or nah?