An electron is smaller than the smallest measurement ever made. We can look into other galaxies, but we do not actually know how big electrons are. We just assume a model that makes sense at certain sizes.
And also this is an overdue post to an outdated website. I know, you’ve heard this before. Believe me, I too cringe at the repetition of my posts. Endure a while longer for me! I’ll make it worth your time, I promise.