Physicists think they've resolved the proton size puzzle
arstechnica.comThat's 0.841x10^-15m.
Now on to the more serious problem: The size of the electron. In physics it's considered a point with a diameter of zero. The experimental upper bound is 10^-22m; it must be smaller than this. Some have theorized that its actual diameter is far below the Planck Length, possibly even under 10^-90m. It's an open question as to whether the electron's diameter can ever be resolved experimentally, and the laws of physics strongly suggest that the answer is that it observation or measurement are impossible even in principle.
...Even the proton's new 0.841 femtometer diameter, smaller than previously assumed, is absolutely enormous in comparison.
Schwarzschild radius for something with the mass of the electron seems like it would be ~1.35*10^-57m. But I guess that is for a neutral object. I suppose the electric charge might be enough to keep it from collapsing into a black hole? I wonder what the smallest Schwarzschild radius is for something with the charge of an electron?
That kind of makes me wonder if quantum mechanics is necessary for gravity to work properly. Like, without tunneling, photons wouldn't be able to escape the gravity of the particles that they originated from resulting in a dead theoretical universe.
In all seriousness, I believe that the resolution of the diameter of the electron would shed a lot of light on the fundamental mysteries of physics and the architecture of reality:
Like, how far below the Planck Length can things go in practice?
What "New Physics" can describe interactions on those scales?
Is space fundamentally granular or continuous?
Is it possible that the electron is a composite of smaller particles, just as the proton is a bag of quarks?
And related to your own musings, what role does quantum foam play?
It's all extremely mysterious and tantalizingly out of the reach of the best conceivable instruments.