Antimatter may be familiar to science fiction as futuristic weapons or spaceship fuel, but does it matter to us here and now?
All the elementary particles that make up the world and the universe have an opposite, a particle with the same mass but opposite charge and quantum property called spin. When a particle meets its corresponding anti-particle the two can annihilate, that is convert their mass into energy, usually in the form of high energy photons. Combinations of anti-particles make up antimatter. The simplest and most common example is the positron, which is the antimatter counterpart of the electron (not to be confused with the proton which is much bigger). The physicist Paul Dirac predicted the positron’s existence when a second, opposite solution popped out of the equations he constructed to describe the electron, and it was found experimentally shortly after, in 1932.
How are positrons important to us?
Positrons have some important applications, particular to modern medicine. Positron Emission Tomography, or PET, is a powerful yet non-invasive tool for looking inside the human body.
While imaging techniques such as X-rays take pictures of the body’s internal organs and bones, PET measures body processes by taking advantage of the positron’s ability to annihilate with electrons. A positron-emitter is attached to a molecule that is important to the human body, such as glucose, then this ‘fake’ glucose fires off positrons as it moves through the body, annihilating them with an electron and producing energy. By looking for that energy researchers can tell exactly where and how the glucose has travelled through the body. This is particularly important because tumours use a lot of glucose, and by imaging them with PET, doctors can tell where these are and how they are responding to treatment.
In the battle against cancer, antimatter matters. By Greg Boyle