The discovery of the positron paved the way for further realization that every particle known must also have an "anti" particle.

The theorization of the positron (or “antielectron” as it should be known) by Paul Dirac in 1828 and its subsequent discovery in experiment in 1932 were not the end of the story for anti-particles – rather, it was very much just the beginning.

It was actually fairly obvious.

More Anti-Particles

A good mathematician could rather easily conclude, after the existence of positrons had been verified, that the principles of “negative energy” do not apply to electrons alone. Rather, they can technically occur for any particle whatsoever. If the right amount of energy is applied to the “sea” of negative energy within an atom, anti-matter counterparts can even be created for the proton, the neutron, and any number of other, more obscure particles in the universe. Every particle (except the photon, which has no charge, and thus could not be distinguished from its anti-particle even if it had one) has its anti-particle counterpart – the antiproton (discovered in 1955), antineutron (discovered in 1956), etc…

Anti-Matter and Virtual Particles

Together all of these particles are known as “anti-matter”, as they form the exact opposite forms of every form of matter known to us.

With the acceptance of antimatter, the question of what constitutes the vacuum of space could finally be answered, and it’s much more complex than most people could have imagined. As photons pass through the negative energy field which comprises everything not occupied by “positive” matter, their energy is constantly allowing particles (and therefore antiparticles as well) to jump in and out of existence, surviving only as long as the initial energy would allow.

These particles, which are really only considered “virtual particles” exist, though they are both fleeting and mysterious, but they are perfectly testable features of the vacuum.

Solid-State Theories

The theory (and eventual discovery) of anti-matter has led many people to some rather interesting conclusions. In 1948, Hermann Bondi, Thomas Gold, and Fred Hoyle collectively proposed what became known as the “steady state” model of the universe, which declared that there must be equal amounts of matter and anti-matter in the universe in order to balance each other out, and that somewhere there must be a part of the universe which was entirely made from anti-matter; antiplanets, antistars, antigalaxies… probably even antipeople with antidogs and anticats and antiFrench toast.

This model on the surface seems as if it would be rather difficult to verify. After all, anti-matter can’t exactly be seen through telescopes (by its nature it would be invisible), so how would one know if it did exist?

Rather simply, actually, for somewhere in the universe the matter and the anti-matter would have to meet. There would have to be a fine line separating the two, and according to both theory and observation, when matter and anti-matter meet up (as they are prone to do, as they are attracted to each other because of opposite electric charges), they “annihilate” each other in a little explosion of energy, according to their mass again according to E = mc².

For just a single particle, this little explosion of energy is not very large, releasing just as single photon of energy – but when one is considering entire galaxies annihilating each other, the explosion should be many times larger than even the greatest supernovas, and even distant traces of this would be rather easily detectable on Earth, even with present technology.

So, there is very little reason to believe in an anti-universe out there, no matter how interesting it might be to ponder, which has led many to ask why. According to many theories, matter and antimatter should exist in exactly equal, perfectly symmetrical, amounts in our universe. So why is it not? What has “broken” this symmetry? That, in fact, is a very complicated question and one which has not yet been answered (though one should keep their fingers crossed, as this is one of the many problems that will hopefully be looked at when the “Large Hadron Collider” begins operation this year in Geneva).

The Truth of Anti-Matter

The fact is that anti-matter, instead of being well-represented in the universe, is a rare, yet mathematically logical occurrence. As much as one may want to think so, there probably are not many antiparticles in the atoms making up things here on Earth, because the particles are simply not energetic enough. It has, however, become rather simple for physicists to create positrons and other antimatter and observe their behavior in particle accelerators, and they can even be stored for a great amount of time within a magnetic field, so there is absolutely no doubt today about their existence.

The important thing that should be gathered here is that the concept and reality of anti-matter is a fantastic proof of the value of mathematics in conveying physical truth (though it is difficult to say if math should be trusted above experiment, or the other way around) and that the universe that humans inhabit is far more complicated than most people have cared to imagine.

References:

Glashow, S. L. (1988). Interactions - A Journey Through the Mind of a Particle Physicist and the Matter of this World. New york: Warner Books.

Gribbin, J. (1994). In Search of Schrodinger's Cat: Quantum Physics and Reality. New York, NY: Bantam Books.

Isaacs, A. (2003). Dictionary of Physics. London: Grange Books.

Kl-Khalili, J. (2003). Quantum: A Guide for the Perplexed. New York, NY: Weidenfield & Nicolson.