Beneath the richness of our world lies a pristine simplicity. Everything is made of a set of just 17 fundamental particles, and those particles, though they may differ by mass or charge, come in just two basic types. Each is either a “boson” or a “fermion.”
The physicist Paul Dirac coined both terms in a speech in 1945, naming the two particle kingdoms after physicists who helped elucidate their properties: Satyendra Nath Bose and Enrico Fermi.
In 1924, Bose was working at the University of Dhaka, in what is known today as Bangladesh. Earlier, around 1900, Max Planck had proposed a law for how much light of each color a hot object emits. (Planck’s insight that this light comes in discrete packets, or “quanta,” set physicists on the path to quantum mechanics.) Bose found a stronger mathematical derivation of Planck’s law. He wrote to Albert Einstein (opens a new tab), asking for help in submitting the result to a German journal, then collaborated with Einstein (opens a new tab) to flesh out the idea.
Bose and Einstein’s math described a situation where multiple particles can be perfectly alike: not just have the same charge, mass and energy but even exist in the same place at the same time. Photons, the particles of light, behave this way. A laser, for instance, consists of many photons synchronized at the same wavelength, together in a single beam. We now call such particles bosons.
The same math would turn out to work for more than just photons. Anything we experience as a force is a collective effort of uncountably many bosons. Photons combine to exert the electromagnetic force, while other bosons give rise to the forces that bind the nucleus together and cause radioactive decay. Physicists expect the hypothetical “gravitons” that produce gravity to be bosons as well. And beyond the fundamental forces, certain composite particles — for example, helium atoms — also behave like bosons.
But Bose and Einstein’s math didn’t work for the electron.
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