We see the world around us – stones, bricks,
earth, wood, plastic, living things and so on. All these are made of atoms and the atoms
themselves are made of protons, neutrons and electrons.
This all changed with the
discovery of a particle by Carl Anderson in 1932 which he called the positron. The positron is
a particle of antimatter and it was the first known particle
of antimatter to be found. It has the same mass as an electron but a positive
charge.
Since then many other antiparticles have been discovered – in fact all the
known particles have their own antiparticles – for example protons and antiprotons. We are
not sure how much antimatter there is in our Universe and we don't really know why there is
the amount that there is. Some people have suggested that when out Universe was form e
another Universe made of mostly antimatter was created at the same time. If it was we must
hope that it never collides with our Universe!
We can make antimatter on a very small scale – a high-energy
gamma ray passing close to the nucleus of a heavy atom can turn into two particles – an
electron (matter) and a positron (antimatter).
When a particle meets an antiparticle
they destroy each other producing a flash of energy – usually gamma rays. Electrons and
positrons annihilating each other have been seen in the
lab.
However if we could do this on a large scale the results
would be catastrophic.
If you were to meet your 'anti-self' (yourself from a Universe of antimatter) then you would destroy each other with a huge flash of energy – about as much as that produced by a severe earthquake!