The world we live in is overwhelmingly made up of particles of matter. But many of these particles have an antimatter equivalent: a particle identical in every respect, but with an opposite charge. So whereas an ordinary electron has a mass of 9.1×10^-31kg and a negative electrical charge of -1, its antimatter version – the positron – has the same mass but a positive charge of +1.

Some particles have no antimatter equivalent. Force-transmitting particles, for example, such as photons and the Higgs boson, are often their own antiparticles, while debate rages about whether the same applies to neutrinos and antineutrinos. In all cases, if an antiparticle were to meet its opposite number, then the two would annihilate in a blast of light and energy.

Some antimatter particles are actually fairly common, as positrons are produced in the beta decays of certain radioactive elements. We actually emit positrons ourselves, thanks largely to the radioactive potassium-40 in our bodies. Bananas and brazil nuts are also regular emitters. These particles don’t hang around for long, though, as they annihilate upon contact with their first electron.

One of the great mysteries surrounding antimatter is why there isn’t more of it around. According to the best models we have of the early universe, the big bang should have produced equal quantities of matter and antimatter. Why, then, do we live in a universe dominated by matter? Many theoretical answers have been proposed, with experimental tests scheduled to be carried out at the particle physics lab CERN near Geneva, Switzerland.

Timeline of antimatter

1898 The physicist Arthur Schuster coins the term antimatter in two whimsical letters to Nature speculating about the negative matter

1928 Paul Dirac’s equation describing the electron indicates the existence of a positive charge antimatter electron – the positron

1932 Carl Anderson discovers the position in cosmic rays

1964 Discovery of CP violation, an asymmetry in processes producing matter and antimatter, in processes involving strange quarks

1982 The Low Energy Antiproton Ring, LEAR, came into operation at CERN with the aim of manufacturing antihydrogen

1995 LEAR makes the first atoms of antihydrogen – but they’re traveling too fast to study

2000 CERN’s Antimatter Factory starts up, using LEAR’s successor, the Antiproton Decelerator

2001 Discovery of CP violation in processes involving bottom quarks

2008 The Large Hadron Collider starts up, with the dedicated LHCb experiment looking at rare antimatter processes

2014 The ASACUSA experiment observes antihydrogen atoms in a “field-free region” needed to make accurate measurements

2017 The BASE experiment at CERN’s Antimatter Factory measures the antiproton’s magnetic moment to an accuracy of 1.5 parts per billion, better than the equivalent proton measurement. The two are consistent

2018 Both the Antiproton Decelerator and the LHC are switched off for upgrades

2019 LHCb discovers CP violation in the process involving charm quarks – the final type of process in which current theories predict it

2021 The upgraded LHC and the new Extra Low Energy Antiproton ring ELENA come online. First antimatter gravity experiments