A pair of researchers predicted a method for turning light into matter 80 years ago, and now a new team of scientists are proposing a technique that could make that method happen in the purest way yet. The proposed method involves colliding two photons — the massless particles of light — that have extremely high energy to transform them into two particles with mass, and researchers in the past have been able to prove that it works. But in replicating that old method, known as Breit–Wheeler pair production, they had to introduce particles that did have mass into the process. Imperial College London researchers, however, say that it's now possible to create a collider that only includes photons.

Theoretical for now, but possible with existing technologyThe researchers' "photon–photon collider," which they're describing in a paper that's being published today in Nature Photonics, works by firing high-energy photons into a field of photons emitted as blackbody radiation. When the photons collide, the researchers believe that a significant number of them will turn from light to matter — more specifically, into an electron and a positron.

What happens in the collider is a matter of Einstein's famous formula at play. With enough energy — a whole, whole lot of it — massless particles can be transformed into matter. In order to get all of that energy, most methods have used electrons to provide a boost. A similar technique is used here, but the critical difference is that this collider keeps all of the electrons outside of the vacuum in which the collision occurs — so matter is actually created in an environment devoid of it. To do that, the researchers propose firing electrons into a gold slab, which would send high-energy photons shooting in the direction of the radiation chamber. Electrons would make it through the gold slab, but they'd all be filtered out from the photons using a magnetic field. The researchers don't say whether they plan on making and testing the new collider, but they say it should be fairly easy to create with existing technology.