For the first time ever, scientist have snapped a photo of light behaving as both a wave and a particle at the same time.
The research was published on Monday in the journal Nature Communications.
Scientists know that light is a wave. That’s why light can bend around buildings and squeeze through tiny pinholes. Different wavelengths of light are why we can see different colours, and why everyone freaked out about that black and blue dress.
But all the characteristics and behaviours of a wave aren’t enough to explain everything that light does.
When light hits metal for example, it ejects a stream of electrons. Einstein explained this back in 1905 by suggesting that light is also made of particles and that those particles of light smack into the metal electrons like billiard balls and send them flying. The insight eventually won him the Nobel Prize, but scientists were not happy about being forced to conclude that light can behave as both a wave and particle.
It’s been over 100 years and every experiment with light that any scientist has ever performed proves that light either behaves as a wave or that light behaves as a particle, but never both at the same time. No one has glimpsed both states simultaneously until now.
But you need a source of light to take a photo, so how do you take a photo of light itself? Researchers at the Swiss Federal Institute of Technology in Lausanne in Switzerland captured the weird split personality of light by using a new photo technique.
First they fired laser light at a tiny metal wire. This trapped waves of light on the wire:
Then they fired a stream of electrons alongside the wire. The light waves on the wire are made of light particles called photons, so the electrons ricocheted off the photons, causing some electrons to speed up and some to slow down. The changes in speed show up as energy blips that can be visualized.
The researchers put the wire under a huge microscope that can see electrons, and snapped a photo of it. The bottom layer of the image shows where the particles of light are and the top layer shows what the light looks like as a wave:
“This experiment demonstrates that, for the first time ever, we can film quantum mechanics — and its paradoxical nature — directly,” Fabrizio Carbone, one of the researchers who worked on the study, said in a press release.
Carbone said the imaging technique could help advance the development of quantum computers — ultrafast computers that take advantage of other strange properties of light particles.
You can watch a video description of the experiment below, from École polytechnique fédérale de Lausanne (EPFL) on YouTube: