Creating Matter From Light: 80-Year-Old Theory Comes To Fruition, Ready For Experiments
It is the stuff only a physicist could dream of - creating matter from light. And after 80 years of theorizing about this dream, a group of Imperial College London physicists proved that it could become a reality.
The idea of creating matter from light was first proposed in 1934 by the scientists Breit and Wheeler, who suggested that the simplest method to achieve this was to smash together only two particles of light (photons), to create an electron and a positron. But this technique had never been observed practically and previous experiments required the addition of massive high-energy particles.
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But this new experiment, published in Nature Photonics, proves the practicality of Breit and Wheeler's theory. In the new experiment, the researchers used a "photon-photon collider," which would convert light directly into matter using technology that is already available. This high-energy physics experiment would recreate a process that was important during the initial 100 seconds after the Big Bang, and that is also seen in gamma ray bursts, which are the biggest explosions in the universe and one of physics' greatest unsolved mysteries.
The solution came by chance when the scientists were working on fusion energy problems, and realized that what they were working on had implications for the Breit-Wheeler theory. Six other theories apart from Breit-Wheeler's, including Dirac's 1930 theory on the annihilation of electrons and positrons and Einstein's 1905 theory on the photoelectric effect, were used to describe the simplest ways in which light and matter interact.
"Despite all physicists accepting the theory to be true, when Breit and Wheeler first proposed the theory, they said that they never expected it be shown in the laboratory," said Professor Steve Rose, from the Department of Physics at Imperial College London, in a press release. "Today, nearly 80 years later, we prove them wrong. What was so surprising to us was the discovery of how we can create matter directly from light using the technology that we have today in the UK. As we are theorists we are now talking to others who can use our ideas to undertake this landmark experiment."
The collider experiment has two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light.
In the next stage, scientists would fire a high-energy laser at the inner surface of a gold can, called a hohlraum, to create a thermal radiation field, generating light similar to the light emitted by stars.
They would then direct the photon beam from the first stage of the experiment through the center of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exit the can.
"Although the theory is conceptually simple, it has been very difficult to verify experimentally," lead author Oliver Pike said in the release. "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. 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!"
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