Physicists Explain How Light can be Converted into Matter

Scientists at the Imperial College London have found a way to convert light into matter.

The idea that massless particles of light - photons - can be converted into matter particles was first proposed by Gregory Breit and John Archibald Wheeler in 1934. They theorized that it could be possible to create matter by smashing together two photons.  The process could lead to formation of an electron and positron. Breit and Wheeler even did the math and found that the theory was quite sound.

However, back then, physicists thought that it was impossible to physically demonstrate the theory because the event would be a rare one and scientists couldn't possibly look at all photon-photon interaction in the experiment.

Researchers have tried showing that matter can be made from light. But, these tests often failed because they had to include particles that have mass.

Now, physicists at the Imperial College London have found a way that could help scientists show that one can create matter from photons only. What's more, the technology needed for the experiments is already available.

Oliver Pike, the lead researcher of the study, said that the experiment would be the most elegant demonstration of Einstein's famous formula. "The Breit-Wheeler process is the simplest way matter can be made from light and one of the purest demonstrations of E=mc2," he told The Guardian.

The research team was actually working on unrelated problems in fusion energy when they found that their study could be helpful in developing an experiment that could demonstrate the Breit-Wheeler theory.

The Experiment

The photon-photon collider experiment proposed by Pike and colleagues involves several steps.

Step one would be to fire an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. These electrons would then be fired into a slab of gold that would create a beam of photons. These photons would have billion times more energy than visible light.

In the next step, scientists would send a high-energy laser into a tiny gold can called hohlraum (German for 'empty room'). The process would create a thermal radiation field, which could generate light as bright as that emitted by stars.

Then, the first beam of photons would be fired into the hohlraum, where the photons could smash into one another.

The team has calculated that the experiment could generate 100,000 electron-positron pairs by forcing high-energy photons to collide in a small space.

"Although the theory is conceptually simple, it has been very difficult to verify experimentally. We were able to develop the idea for the collider very quickly, but the experimental design we propose can be carried out with relative ease and with existing technology," Pike said in a news release. "Within a few hours of looking for applications of hohlraums outside their traditional role in fusion energy research, we were astonished to find they provided the perfect conditions for creating a photon collider. The race to carry out and complete the experiment is on!"

Their study is published in the journal Nature Photonics.

The study is also important because the experiment could enable researchers to find more about the first 100 seconds of the Universe. Also, the research could explain powerful explosions in the Universe called gamma ray bursts.

The research was funded by the Engineering and Physical Sciences Research Council (EPSRC), the John Adams Institute for Accelerator Science and the Atomic Weapons Establishment (AWE), and was carried out in collaboration with Max-Planck-Institut für Kernphysik.