Thursday, April 06, 2006

Tech: subatomic particles: why you don’t know much (and nor do I)

This is a test.

1. How many subatomic particles are there? (name them)
2. How many elementary particles (ie can’t be divided)?
3. How many stable particles?
4. How many different properties categorise them?

How’d you go? I wanted to clarify what I thought I know, which is why I read up on them. I scored poorly, so don’t feel bad. Answers at the bottom.

Sub-atomic particles are, of course, particles smaller, than an atom. Off the top of your head, you’d surely remember protons, neutrons, and electrons. Well, you’d already be two up on a lawyer I just asked. You’d remember the periodic table, where different elements had different numbers of those three. Maybe you could say that ions are atoms with a few electrons added or removed, and isotopes are atoms with a non-standard number of neutrons. Like me, you may also have heard of quarks, neutrinos, mesons, gluons… and then get confused. Well, here goes a quick count.

First I should warn you: nearly every particle has a corresponding anti-particle. This is anti-matter. However, I doubt you could put together a glob of scary anti-matter as in Star Trek. Most of these particles only exist separately for brief periods of time, in small amounts, within labs.

Sub-atomic particles are categorised by five types of properties: mass, electrical charge, spin, magnetic moment, and interaction. The only stable ones are electrons, protons, and… neutrinos. The neutron is stable only inside an atom’s nucleus.

The most elementary particles are the sets of quarks, leptons, and gauge bosons. There are six types of quarks: up, down, top, bottom, strange, and charm. For each, there is an antiparticle, and they come in three different varieties. In total: 36 types of quarks (protons and neutrons are each made of three quarks). There are 12 leptons: electron, muon, and tau, their neutrinos: electron neutrino, etc – as well as their antiparticles. There are four gauge bosons: gluon, photon (yes), weakon, and graviton.

This is only the start, but I think that’s plenty enough. The answers are:
1. Over 300!
2. 52!
3. 8, by my reading
4. 5.

So much for protons, neutrons, electrons. Why didn’t I know all this already? I suspect that most of this wasn’t commonly accepted when I was at school/university, and/or most of it was post-grad stuff. At least I know why I’m confused now. Despite knowing more.

Reference: Lafferty P & Rowe J: The Hutchinson Dictionary of Science, Helicon, Oxford, 1994.

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