Why the Electron Is Too Perfectly Round

Sleep On Physics

Sleep On Physics

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The electron is the most perfectly round object ever measured. If you scaled one up to the size of the entire solar system, any lopsidedness in its charge would be smaller than a human hair. But here's the problem, according to almost every theory trying to explain the biggest mysteries in physics, the electron shouldn't be this round. Supersymmetry, extra dimensions, new Higgs particles, they all predict a tiny distortion that experiments should have already found. And yet, measurement after measurement finds the same impossible answer: perfect roundness.

This isn't just a quirky fact about a subatomic particle. The electron's shape is one of the most powerful tests of new physics ever devised. A single tabletop experiment measuring the electron electric dipole moment can probe energy scales far beyond what the Large Hadron Collider will ever reach. And right now, that measurement is quietly destroying some of the most celebrated ideas in theoretical physics.

In this video, we explain what physicists actually mean by the electron's "shape" (it's not what you think), why the Standard Model predicts near-perfect roundness, why almost every proposed fix to the Standard Model predicts something measurably different, and how scientists use heavy molecules like thorium monoxide and hafnium fluoride ions to hunt for a wobble smaller than anything ever measured before.

The electron knows something about the deepest laws of nature. The question is whether we can build instruments precise enough to read the answer.

Sources:

Roussy, T.S., Caldwell, L., Wright, T., Cairncross, W.B., Shagam, Y., Ng, K.B., Schlossberger, N., Park, S.Y., Wang, A., Ye, J. & Cornell, E.A. (2023). "An improved bound on the electron's electric dipole moment." Science, 381(6653), 46-50. https://doi.org/10.1126/science.adg4084

Andreev, V. et al. (ACME Collaboration). (2018). "Improved limit on the electric dipole moment of the electron." Nature, 562(7727), 355-360. https://doi.org/10.1038/s41586-018-05...

Pospelov, M. & Ritz, A. (2005). "Electric dipole moments as probes of new physics." Annals of Physics, 318(1), 119-169. https://doi.org/10.1016/j.aop.2005.04...

Hudson, J.J., Kara, D.M., Smallman, I.J., Sauer, B.E., Tarbutt, M.R. & Hinds, E.A. (2011). "Improved measurement of the shape of the electron." Nature, 473, 493-496. https://doi.org/10.1038/nature10104

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