There are a few ideas out there that have fascinating scientists for millennia. Some of those bugbears have been somewhat disproved, even lowered to the level of pseudoscience; think of alchemy and time travel. As physics becomes enormously more sophisticated, however, some of these impossibilities have become possibilities again. One such fascination is the concept of creating matter out of light. A group of British scientists at the Imperial College London have just announced that this is exactly what they intend to do – before the end of the year.
Predicted 90 Years Ago…
British Physicist Paul Dirac
Considering the nature of the proposition, which sounds almost miraculous to the nonscientific, it is worth noting that it is a lot less fantastic an idea than one might imagine. In its essence, the creation of matter from light is an expression of the world’s most famous scientific equation, E=mc2. What’s more, a paper written in 1930 by Paul Dirac, a British theoretical physicist, described how photons, or light particles, could be created through the collision and annihilation (or combination) of physical matter in the form of an electron and a positron, its antimatter equivalent.
Even more encouragingly, American physicists Breit and Wheeler wrote in a 1934 paper that the converse must also be true, describing the process in a paper that was widely accepted by the scientific community. They warned, however, that it would be “hopeless to try to observe the pair formation in laboratory experiments”. This rather downbeat analysis was generally accepted, and there it was left for over half a century.
As Lab Equipment Develops, So Too Do the Possibilities
Today, it seems the long wait may be over. Science has changed beyond recognition in the interim, and so too has the equipment available to scientists. Modern day lab equipment is of a higher standard than ever before, and much of the advanced equipment available in many labs around the world would have been inconceivable in the time of Breit and Wheeler.
Amongst lab machines which are now relatively easy for physicists to gain access to are ‘hohlraums’. Named for the German word for ‘hollow room’, this machine takes the form of a hollow golden canister into which a high powered laser can be fired, creating a field of thermal radiation which creates light comparable to the light of stars. The device, upon which the new paper written at the Imperial College London relies, was discovered to be ideally suited for creating the sort of conditions that Breit and Wheeler thought were ‘hopeless’ back in 1934.
The plan is surprisingly simple. Breit and Wheeler had a key problem, namely that their theory was almost impossible to carry out in a measurable way. The collision and annihilation (combination) of two photons is the occurrence needed to produce matter, but this is an incredibly rare event and the small size of photons makes the likelihood of it less likely still. The experiment could be carried out thousands of times with no visible success, despite the theory being solid.
Ladies and gentlemen; The ‘Hollow Room’.
The hohlraum changes this. Oliver Pike, who led the study, praised the simplicity of the original 1934 theory and agreed that realising it in a laboratory was the problem. However, on examination of the hohlraum, his team discovered that it could produce a field of photons so dense that the likelihood of a collision if this was hit by another beam goes up enormously.
In the beginning…
The second ray of photons, as proposed by the paper, would be created by a high power laser which could be fired into a plate of gold, creating a dense gamma ray. This gamma ray would then be directed towards the hohlraum which, by means of another powerful laser, could be made to create a dense enough field of photons as to raise the likelihood of collisions occurring to the point where the experiment becomes truly viable.
This plan is one which they are optimistic about seeing through to gaining a set of results in the very near future. In fact, Pike along with Steven Rose, co-author of the paper, hope to be able to carry out the experiment which they have described ‘within a year’. This would be a huge moment for physics that, since its theoretical realisation in 1934, has remained one of the last pieces of the puzzle of light’s relationship with matter.
British Pioneering Science to Lead the Way?
It is also a coup for British science. Universities, laboratories and the wider industry have been under huge financial pressure as the UK has suffered a long recession followed by a period of government austerity measures. While the Chancellor, George Osborne, has said that British science is a priority for government, the scientific community are eager to prove that it really does pay to invest, and that investment in the best equipment and the latest technologies can yield ground breaking results.
As Pike commented, the ‘race is on’ to carry out the experiment. As far as British science is concerned, the prize for winning that race – a major ‘win’ for British science – is a doubly coveted one.