Question: How big is the smallest electron you've discovered?

Jony Hudson answered on 12 Nov 2011:

That’s a really good question.

Actually – believe it or not – nobody really knows how big the electron is! And what’s even weirder, how big it is could even depend on how you measure it.

The problem is, how do you measure something that small? You can’t use a ruler, because the ruler is too big. In fact, you can really use anything, because everything is bigger than the electron.

So what they do is they make really clever measurements where they watch how the electron spins around in a magnet. And they can prove that the electron is smaller than 0.0000000000000000001 cm. But it could be even smaller than that, they just don’t know.