3 ms·
It's true that there's a sense in which the size of the proton is undefined. But there is also a sense in which it is very precisely defined, which is the root
by om2 9y ago
It's true that there's a sense in which the size of the proton is undefined. But there is also a sense in which it is very precisely defined, which is the root mean square of the electron scattering cross-section. This can be measured very accurately. And that's what the article is talking about.
https://en.wikipedia.org/wiki/Charge_radius https://en.wikipedia.org/wiki/Charge_radius
- Koshkin 9y ago> the root mean square of the electron scattering cross-section Thank you, and I wish the article had said that.
- davrosthedalek 9y agoWhile you can measure it via scattering, it's not the square root of the scattering cross section. The radius is defined via the slope of the proton electric form factor at Q^2=0. This translates to the root mean square radius, that is the sqrt of the integral of r^2 weighted with the density, i.e. sqrt ( Integral r^2 rho(r)).
- deleted 9y ago[deleted]
- dboreham 9y agoHmm...perhaps it has been edited since but that's exactly what the parent says.