The Mysterious World of Anti-Matter

“How do we exist in a matter-dominated universe?’‘Anti-matter occurs more frequently than initially believed, and is not only on the Star Trek Enterprise’

Nearly 90 years after initial discovery, John Savage talks the who, when, what and how of anti-matter, one of physics’ greatest mysteries.ANTI-MATTER is quite a scientific curiosity, and was originally conceived of by the British physicist Paul Dirac in 1928. Dirac devised an equation to describe the behaviour of an electron moving at relativistic speed and in doing so created an equation with two solutions: either an electron with positive energy or an electron with negative energy.He interpreted this result to be that for every particle there was a corresponding ‘anti-particle’ that was identical to the original particle in almost all aspects but charge, for which it was the complete opposite.In 1932, Carl David Anderson, an American physicist, discovered the anti-matter equivalent of the electron present in cosmic rays and christened it the ‘positron’. Within twenty-five years, both the anti-proton and the anti-neutron were discovered. The anti-neutron was intuitively quite puzzling as it has no charge that could have an opposite value, yet it was realised that the charged subunits (or ‘quarks’) themselves were of an opposite charge. Quarks and anti-quarks were only proposed to exist in 1964, almost a decade after the anti-neutron was discovered.It was subsequently theorised that at the occurrence of the Big Bang, an equal amount of matter and corresponding anti-matter should have been created. Upon interaction with matter, anti-matter causes both particles to be annihilated and two photons of light are produced. Each have energy corresponding to the mass of the particles annihilated and they both move in precisely opposite directions.This leads to one of the great mysteries of theoretical physics: how do we exist in a matter-dominated universe? What could have happened was that all of the anti-matter and most of the normal matter was destroyed. It is this asymmetry that stumps physicists.Other theories in the field include the concept of an ‘anti-matter universe’, which so far is only the stuff of comics and sci-fi writing.Unbeknownst to most, anti-matter occurs more frequently than initially believed, and is not only on the Enterprise from Star Trek. Positrons that emit gamma rays indirectly are utilised in the diagnostic process of positron emission tomography (PET). It is a form of 3D imaging that is used to observe metabolic processes in the body and can be used in the areas of oncology, neuroimaging and cardiology in hospitals.Anti-matter is known to occur naturally through a type of radiation referred to as ?-decay of radioactive isotopes and was originally observed from cosmic rays. Scientists have observed antimatter present in thunderstorms, as the anti-matter enters our atmosphere through the medium of cosmic rays.We have created miniscule amounts of anti-matter over decades of research, and the brilliant minds at CERN have succeeded in even creating anti-atoms of ‘anti-hydrogen’. This ‘anti-hydrogen’ is composed of an anti-proton and a positron, compared to hydrogen which is composed of a proton and an electron.The creation and storage of such a problematic material is possible. But, like all things on the frontiers of scientific discovery, it is quite expensive, so don’t expect anti-matter spaceships anytime soon.