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An introduction to the science of anti-matter
Anti-matter can be described as the mirror of matter, containing anti-particles of the particles that constitute normal matter. Anti-particles are equal and opposite to matter particles in that they have an opposite charge and they rotate in an opposite direction. So whereas matter is composed of atoms, that are made up of the elementary particles (electrons, protons and neutrons), anti-matter is composed of anti-atoms that are made up of positively charged electrons known as positrons, negatively charged protons known as anti-protons, and anti-neutrons. Most theorists believe that at the time of the Big Bang anti-particles and particles were created in almost equal numbers.
So is there any anti-matter in the universe now?
If there was anti-matter around us, it would annihilate with matter and we would see light coming out. In terms of anti-matter somewhere else in the universe, most theorists believe that the universe is made up of all matter, however, they are not one hundred per cent sure. Physicists have used special orbiting equipment to measure the sky at a range of energies that should have detected anti-matter annihilation, but none of the instruments have uncovered evidence for vast amounts of anti-matter in the universe. There is evidence that in some isolated spots in the universe some very energetic reactions are taking place that create anti-matter which then annihilates, however, this is not thought to be residual anti-matter left over from the Big Bang. The reason for the lack of anti-matter in the universe since the Big Bang is a matter of scientific debate.
Applications of anti-matter
Currently, the main use for anti-matter is for medical diagnostics, where positrons are used to help identify different diseases with the Positron Emission Tomography or PET scan. When a positron-emitting tracer is injected into a patient's body or a piece of machinery, the positrons soon annihilate with the surrounding atoms. When this happens they emit a characteristic radiation signature which quickly pinpoints where the annihilations took place. Therefore, these PET radiographs reveal inner structures quickly and with low doses of positrons. They are particularly widely used in brain scans, both for medical diagnosis and for revealing how the brain itself works. The other great use for anti-matter is scientific research.
Future of anti-matter
At the moment, our methods of producing anti-matter are rather inefficient and the current worldwide production rate of anti-matter is less than a gram per year! Much research is being carried out into the possible future applications of anti-matter but first we need a reliable method of producing large amounts of it.
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Content last updated: 16/06/2000
