AKA: All electrons in existence are actually all the same electron.
Theory born: 1940
Parent(s): John Wheeler
Description: There are a number of intriguing observations which can be made about the nature of electrons. The first of these is that all electrons, regardless of source, have exactly the same properties. The second is that they all behave in exactly the same way. In the spring of 1940, Professor John Wheeler shared his theory about why this was so with his doctoral student Richard Feynman (yep, that Richard Feynman).
He proposed that there was only one electron and that this single electron travelling forwards and backways in time accounted for all electrons in existence.
Imagine that there's a tangled ball of string. Now imagine slicing a straight line through that ball of string. The exposed ends of the string that you see are electrons; the plane you sliced through the ball is 'now' as a moment of time.
Now, strictly speaking, according to this theory, they're not all electrons and this is where the theory comes unravelled (a string joke, you see). Mathematically, an electron travelling backwards in time becomes a positron, the antimatter counterpart of an electron. If there is only one electron, then there should be an equal number of electrons and positrons in the universe (because every time the electron has travelled forwards in time, it then needs to travel backwards in time). To return to the ball of string analogy, there will be as many strands travelling upwards as there are strands travelling downwards.
It's been proven conclusively, however, that there are many more electrons than positrons in existence. Wheeler himself acknowledged this as a problem.
"Maybe they are hidden in protons or something”, he joked at the time. He later wrote in his memoirs:
"I knew, of course, that, at least in our corner of the universe, there are lots more electrons than positrons, but I still found it an exciting idea to think of trajectories in spacetime that could go unrestricted in any direction — forward in time, backward in time, up, down, left, or right."
Wheeler did leave himself a small loophole in his statement above: that our position in the universe is different from others, that those other places have a balance of electrons and positrons (and enough extra positrons to balance their lack in our part). Unfortunately, that violates the cosmological principle: that we don't occupy a special place in the universe, a fundamental assumption in astrophysics.
Could the One-Electron Universe still be true then? Possibly, but if the cosmological principle was shown to be invalid, then a great deal of physics would need to be reexamined. The theory of quantum electrodynamics also would seem to invalidate the theory, but that's a story for another day!
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