What Is Antimatter? A Clear Explanation

Antimatter sounds like science fiction, but it is real, it is made in laboratories every day, and a version of it is even used in hospitals. It is the mirror image of ordinary matter: same mass, opposite electric charge.

Matter’s mirror twin

Every particle of ordinary matter has an antimatter partner. The electron’s partner is the positron — identical mass, but positive instead of negative charge. The proton’s partner is the antiproton. Put a positron and an antiproton together and you can even build an anti-hydrogen atom, which scientists at CERN have done.

Annihilation: matter meets antimatter

Here’s the dramatic part. When a particle meets its antiparticle, they annihilate — both vanish, and their mass converts entirely into energy, following Einstein’s E = mc². Gram for gram, this is the most concentrated energy release known to physics: far beyond nuclear fission or fusion.

That is why antimatter is a staple of fiction as the ultimate fuel or weapon. In reality, we can only make it in vanishingly tiny amounts, and storing it is extraordinarily hard, since it destroys itself the moment it touches ordinary matter.

The great cosmic mystery

Here is one of the biggest unsolved problems in physics. The Big Bang should have produced equal amounts of matter and antimatter — which would have annihilated completely, leaving a universe of pure energy and no galaxies, stars or people.

Yet here we are. For some reason, matter slightly outnumbered antimatter in the early universe — by about one part in a billion — and that tiny surplus is everything we see today. Why this asymmetry exists is a frontier question that experiments at CERN and elsewhere are still probing.

Antimatter is already useful

You may have benefited from antimatter without knowing it. A PET scan — positron emission tomography — uses positrons emitted by a tracer to image the body in fine detail. The annihilation of those positrons with electrons is what the scanner detects.

Related: what is dark matter? — a different cosmic mystery entirely.

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