Pretty much everything in the universe is made out of matter - the earth, air, you and
me, stars, interstellar dust - all matter. By which we mean that these things are made
out of electrons and quarks - and very occasionally other rarer matter particles like muons, tauons,
and neutrinos.
All of these particles are, at their fundamental level, excitations in everywhere-permeating
quantum fields. But, as the famous quote goes, “for every particle, there is an equal and
opposite antiparticle - an opposite excitation in the everywhere permeating quantum field
that has all of the exact same properties as that particle - except opposite charge.”
And since these antiparticles are opposite excitations of the quantum field, when a particle
and antiparticle meet, they annihilate and destroy each other!
Which is pretty much exactly like how the equation x^2=4 has two solutions: 2 and -2,
with the same value but opposite sign. And when they meet, they annihilate!
Every fundamental particle has an antiparticle: there are antiquarks, antineutrinos, antimuons,
antitauons, and of course antielectrons - though we call them positrons.
Since antimatter particles are essentially identical to regular matter other than the
opposite charge thing, they can combine together in essentially identical ways to form antiprotons,
anti-atoms, anti-molecules, and, in principle, anything from anti-ants to anti-matterhorns.
But we can also make the really cool positronium atom
- it’s like hydrogen, except instead of an electron orbiting a proton,
it’s an electron orbiting a POSITRON. Until they annihilate each other in under a nanosecond.
because every particle of antimatter annihilates with regular matter upon meeting, it’s really
hard to make anything big out of antimatter - at this point we’re still only able to
make and contain a few hundred antihydrogen atoms at one time.
And when they annihilate, the energy of particle and antiparticle has to go somewhere, which
is why matter/antimatter annihilations have been proposed as bombs. But naturally-occuring
antimatter is hard to come by. So, unlike a uranium fission bomb, which allow us to
release the bottled energy of the supernovas that forged the uranium in the first place,
you’d have to put all the energy into an antimatter bomb yourself by making antimatter.
Which you do by agitating empty space into pairs of matter and antimatter excitations.
Kind of like hitting zero with a hammer to get out 2 and minus 2, except instead of a
hammer, you use a particle accelerator or high-energy photons of light.
Photons, incidentally, have zero charge and so are their OWN antiparticles, in the same
way that zero is equal to negative zero!
In fact, mathematics has always been closely tied to antimatter: the mathematics of relativisitic
quantum mechanics predicted the existence of antimatter before any had ever been discovered.
The fact that there’s so little antimatter around in the universe TO discover is both
an obvious thing (because if it were around, it would have destroyed us), a good thing
(because it can’t destroy us), and a puzzling thing - if matter and antimatter are basically
identical “mirror” images of one another, why did the big bang produce so much more
matter than antimatter?
No one knows - though to physicists, the answer matters.