The spatial extent of a proton keeps returning different results:
What does it mean for a subatomic particle to have a measurable “size”? Mathematically, fundamental particles are idealized as point particles, which is to say that, as far as we can tell, they have no meaningfully discernible spatial extent, or substructure, at all. True, all fundamental particles are associated with a quantum mechanical wave packet, which does have a spatial extent that depends on the energy of the particle. Yet these basic bits of Lego are entities whose wave packets you can, in principle, pack into as small a region as you’d like before the very notion of continuum geometry starts, at the Planck scale, to lose meaning. Fundamental particles organize into something analogous to a mini periodic table—consisting of the various force carrying particles, such as photons and gluons (the carrier particles of the strong nuclear force), along with three generations of quarks and leptons and the mass-generating Higgs boson—and can stack together in different combinations to form a zoo of so-called composite particles.
Subodh Patil, “A Breakthrough in Measuring the Building Blocks of Nature” at Nautilus
A research team found a way to arrive at a more precise value.
Although this convergence, based on the continued refinement of experimental techniques, did not deliver the new physics some may have been hoping for, even the most despondent theoretical physicist can acknowledge the experimental artistry that seems to be bringing the matter closer to conclusion. What remains unresolved is the reason why measurements, relying on different spectroscopic methods in atomic hydrogen, return different values for the charge radius of the proton. The mystery, and along with it, the diminishing hope of particle physicists, endures for the time being.
Subodh Patil, “A Breakthrough in Measuring the Building Blocks of Nature” at Nautilus
Diminishing hope for new physics? That isn’t the triumphant scientism we were told to expect.