Re: What are things that are not made up of matter?

Dear Arwin,

This is one of the best questions I've yet received on MadSci!

I like your definition of matter, but I think we really need to expand it a
little bit. As a particle physicist, I send to think of "matter" as
anything that's made of quarks and/or leptons. Quarks, as you may know,
come in six different flavors, namely, up, down, strange, charm, top, and
bottom. They have electric charges of either -1/3 or +2/3 that of the
proton. Quarks interact with each other and with leptons via the strong,
electromagnetic, weak, and gravitational forces [I'll get back to forces in
a bit.] The theory that describes the behavior of quarks is called quantum
chromodynamics; it requires that all quarks exist either in groups of two
(quark and anti-quark) or three (all quarks or all anti-quarks). Protons
and neutrons are made of up and down quarks; matter made of any of the
other four quarks is unstable and decays quite rapidly.

Leptons also come in six different types, namely, electrons, muons, taus,
and a neutrino for each one. Electrons, muons and taus all have charge -1
times that of the proton, and the neutrinos have no charge (neutrino is
Italian for "little neutral one"). Electrons, et al, interact via the
electromagnetic, weak, and gravitational forces. Neutrinos, since they have
no charges, interact only via the weak and gravitational forces. For many
years we thought that neutrinos were massless; that would have meant that
neutrinos only interacted weakly. However, since they have mass, we know
that they can also interact via gravity. 

So, there you have it-- those are all the kinds of matter that we've ever
seen. We can discuss anti-matter if you like (anti matter is the same as
matter but has the opposite electrical charge) but there's not a real
difference between the two for our purpose.

What's left? Well, there are those forces that I mentioned earlier. The
forces govern the interactions between particles. The strong force holds
together protons and neutrons and atoms; the weak force governs radioactive
decay; the electromagnetic force is, well, electricty and magnetism and
light; and the gravitational force is gravity. When things interact via a
given force, that means that the "force carriers" for that kind of force
are exchanged. When you drop something and it falls to the floor, gravitons
are exchanged. Gluons, the mediator of the strong force, are exchanged
among quarks and among protons and neutrons to make atoms. And so on. So
really, each force mediator-- gluons, photons (for the electromagnetic
force), the W and Z (for the weak force), and the graviton-- are the
physical manifestation of that kind of energy. Are they matter? It's hard
to say, as we can make most (all but the graviton) in the lab, watch them
decay & interact, and predict their behavior. 

A good foray into the world of particle physics is "The God Particle" by
Nobel Laureate Leon Lederman.

I hope this helps!