Antimatter is useful
Antimatter is real
Antimatter isn’t science fiction, and it’s not just some theoretical abstract in an equation. Antimatter is real, and we put it to good use every day. Antimatter helps us do all sorts of things, from keeping food fresh to saving lives.
But how can we make use of antimatter, if it annihilates with matter?
Annihilation… but not yet
When a particle and its antiparticle come together they always annihilate, but they don’t always annihilate immediately. In particular, an electron and its antiparticle (a positron) can sometimes get along together, just for a moment.
|Instead of annihilating straight away, the electron and the positron can go into orbit around one another.
When they do that, they form an unusual, short-lived “atomoid”, called positronium.
Positronium isn’t really an atom
Positronium doesn’t have a heavy nucleus of protons and neutrons at its centre, like an atom does. Positronium doesn’t have anything at its centre. The electron and the positron have opposite electrical charges but the same mass, so they form an equal partnership, mutually orbiting one another.
Positronium doesn’t last long
In fact, whenever a positron and electron come together, they’ll always annihilate eventually. Even if they form positronium first, this just delays the annihilation by about 140 billionths of a second.
Animation credit: Alexander Ocias
It’s all about positronium
Although it lasts such a short time, positronium is the key to almost all the practical applications of antimatter.
When positronium forms, it delays the annihilation of electrons and positrons, and this delay can tell us a lot about the conditions where the positronium formed.
So positronium lets us look deep inside the structure of materials, even deep inside the human body.
How do we use positronium?
Although positronium can only survive about 140 billionths of a second, studying its lifetime tells us a lot about its environment.
We can use positronium to investigate all sorts of materials, but it survives best in soft materials, such as soft plastics and membranes.
We know that positronium survives well (that is, up to about 140 billionths of a second) in any material with large open spaces. This includes living organisms, so positronium can be a powerful tool to look inside our own bodies.