Famous Einstein equation used to create matter from light for first time

The STAR detector at Brookhaven National Laboratory detected the matter-antimatter pairs created by the colliding light.

(Image credit: Brookhaven National Laboratory)

In a stunning demonstration of one of Einstein's most famous equations, physicists are claiming to have created matter from pure light for the very first time.

Albert Einstein's famous E=mc2 equation says that if you smash two sufficiently energetic photons, or light particles, into each other, you should be able to create matter in the form of an electron and its antimatter opposite, a positron.

But this process, first described by American physicists Gregory Breit and John Wheeler in 1934, has long been one of the most difficult to observe in physics — mainly because the colliding photons would need to be highly energetic gamma rays, and scientists are not yet able to make gamma ray lasers. Alternative experiments have shown matter being produced from multiple photons, but never in the one to one way needed to most conclusively prove the effect.

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Instead of accelerating the photons directly, the researchers sped up two ions — atomic nuclei stripped of their electrons and therefore positively charged — in a big loop, before sending them past each other in a near collision. As the ions are charged particles moving very close to the speed of light, they also carry an electromagnetic field with them, inside of which are a bunch of not-quite-real 'virtual' photons "traveling with [the ion] like a cloud," Xu explained.

Virtual particles are particles that only pop into existence very briefly as disturbances in the fields that exist between real particles. They don't have the same masses as their real counterparts (unlike their real counterparts that have no mass, virtual photons do have a mass). In this experiment, when the ions zipped past each other in a near miss, their two clouds of virtual photons were moving so fast they acted as if they were real. The real-acting virtual particles collided — producing a very-much-real electron-positron pair that the scientists detected.

When two real particles collide, the secondary products should be produced at different angles than if they were made by two virtual particles. But in this experiment, the virtual particles’ secondary products bounced off at the same angles as secondary products from real particles. So, the researchers could verify that the particles they were seeing were behaving as if they were made by a real interaction. They had successfully demonstrated the Breit-Wheeler process.

Ben Turner is a U.K. based writer and editor at Live Science. He covers physics and astronomy, tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.