Electrons are proficient little magicians. They seem to flit about an atom without tracing a particular path, they frequently appear to be in two places at once, and their behavior in silicon microchips powers the computing infrastructure of the modern world. But one of their most impressive tricks is deceptively simple, like all the best magic. Electrons always seem to spin. Every electron ever observed, whether it’s just ambling its way about a carbon atom in your fingernail or speeding through a particle accelerator, looks like it’s constantly doing tiny pirouettes as it makes its way through the world. Its spinning never appears to slow or speed up. No matter how an electron is jostled or kicked, it always looks like it’s spinning at exactly the same speed. It even has a little magnetic field, just like a spinning object with electric charge should. Naturally, physicists call this behavior “spin.”
But despite appearances, electrons don’t spin. They can’t spin; proving that it’s impossible for electrons to be spinning is a standard homework problem in any introductory quantum physics course. If electrons actually spun fast enough to account for all of the spinlike behavior they display, their surfaces would be moving much faster than the speed of light (if they even have surfaces at all). Even more surprising is that for nearly a century, this seeming contradiction has just been written off by most physicists as yet another strange feature of the quantum world, nothing to lose sleep over.
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