It’s not a big deal.

By that, I meant that “quantum” does not mean “big.” (This is a peeve of mine. Not so sure it’s a pet peeve. Perhaps a feral peeve?) I ran across a blog entry about the use of quantum that wasn’t wrong as it usually is. (But the blog is by a physicist, so there you go.) Now the entry is a little awkward in that, at the end, it seems to imply that quantum means “small,” and it doesn’t mean that either. But quantum things are usually small, which is why the use of the phrase “quantum leap” is doubly irritating to a pedantic, anal meticulous physicist. Years ago I tried convincing Phil Plait of this, back when the Bad Astronomy website was an only child (no forum, no blog, just posts that addressed misconceptions), but he politely disagreed, though he thought my day job was cool. But he was wrong (about the former, not the latter).

The “opposite” of quantum is continuum, because quantum means discrete. A quantum jump can be the smallest possible transition there is. If I were to offer you a quantum pile of money (and for a limited time, for only five dollars!) it could be whatever number of pennies constituted a “pile” because the penny is the quantum of currency (in the US, at least). Money is discrete, not continuous. Now, it doesn’t have to be small, either. That’s just it — size isn’t inherently part of the definition. “Quantum leap” doesn’t really tell you anything. You need to know what the quantum unit is; if the leap is actually big it should involve many quanta. If it only involves one, then it means it’s the smallest leap possible, and you shouldn’t be impressed.

The comment “Perhaps, just perhaps, we’ll finally have an example of quantum meaning small!” is probably better stated as “Perhaps, just perhaps, we’ll finally have an example of quantum being small!” since most quantum things in physicsland are small.