p.s.
Whoever invented USB deserves a gold star. I was having a touch of carpal (I think maybe because I read about
Sometimes when you can’t actually have pleasure, you have to settle for lack of pain.
I wonder..
(Now there’s a phrase that can get me into trouble)
The other day, when I flew a simulated plane over my house, I told Kayti she couldn’t hear it because it was the size of a electron. She responded with ‘And just how big is a electron, anyway?’ – and I haven’t a clue. So, can anyone tell me, in metric-system-friendly units? This isn’t like a assignment or anything, but if anyone happens to be like ‘oh, i know, i know’.. it’d be cool if ya commented! Bonus points if you can also tell me how we know.
April 2nd, 2006 at 8:26 pm
A tiny speck of electric charge, so-far impossible to break into smaller pieces, weighing in at 9.109 × 10-31 kg and a charge of 1.602 × 10-19 Coulombs. An electron is so small that its ‘size’ is a nebulous concept; if it were a little round ball, it would be about 10-15 m across.
April 3rd, 2006 at 7:56 pm
Although some will opine that an electron doesn’t actually have a size, that it’s a wave continuously distributed across the entire universe but 95% of its interactivity is concentrated in a space about 10e-15 m across. And it depends on what the electron is doing: just hanging out around its single parent, that 95% will be spherical, but when it’s one of the electrons forming a covalent bond between two atoms, that 95% is distributed in donut or dumbbell or whirled-flower-petal shapes.
USB is okay. I wish firewire had taken off. But USB seems to be easier to write receiver drivers for.
April 6th, 2006 at 3:34 pm
The classical electron radius is indeed 3e-15 m, and you can see a simple derivation of this result at http://scienceworld.wolfram.com/physics/ElectronRadius.html.
Quantum mechanics tells us that an electron can only be described in terms of a probability distribution, from which we can extract a limited amount of information about its state (e.g. position, momentum) but renders the notion of size irrelevant. You can calculate the volume over which a given probability density (square of the wavefunction) exceeds some minimum value, but at that point you’re no longer talking about a tangible particle.
There is one general context in which electrons do behave much like charged balls of radius 3e-15 m: low energy (i.e. non-relativistic) free states. Electrons bound in atomic orbitals are in momentum eigenstates and thus about as non-tangible as possible, while relativity does some very strange things to charged particles.
Ask me on Brig if you’re still curious. 😉
-D.