The only electron
Imagine you were a time traveller who could also live while time was reversing. Only every time you go back and forth, you are a different you. Doing it so many times, you now have a whole town of yourself, half of them doing things normally, and half of them walking, talking and acting backwards. I’m sure some of us would love to see a whole citadel of ourselves living working and interacting, but perhaps it wouldn’t last long before it drove you mad. Although its something that should remain in fiction, sometimes crazy ideas lead to interesting leaps in science.
In 1939, an excited professor and supervisor, John Wheeler called up his student Richard Feynman at a ridiculous hour. “Feynman, I know why all electrons have the same charge and the same mass” “Why?” “Because they are all the same electron!” “*gasp”.
This world line describes the path that a single electron takes through space and time.
Moving horizontally is caused by interactions with the forces of nature and collisions with photons, moving the electron around in space.
When the world line travels downwards, (backwards through time) it is a positron and when it travels upwards, it is an electron.
If we were to zoom closer in, to the inside of the red box, then all we see is 2 different electrons and a positron. If this were the case, but with 10^80 bends instead, then you would get around the right number of electrons in the universe, all accounted for by one unbroken world line.
Although there is currently no other good explanation for why these electrons are perfectly identical to any level of accuracy you can measure too, the one electron universe does have some holes. The most problematic one is that according to the electrons world line, there should be equal amounts of electrons and positrons. This is doesn’t seem to be the case, as we know electrons greatly outnumber their backward counterparts. So either the idea is wrong, or the all the missing positrons are hiding somewhere.
But Richard Feynman didn’t take the one electron universe as seriously as he took the idea of positrons being time reversed electrons. This insight was the inspiration for his future contribution to physics, where he later won the 1965 Nobel prize in physics with Julian Schwinger and Sin-Itiro Tomonaga. The Feynman diagrams he used, were a way of analysing the behaviour of subatomic particles by drawing out every possible interaction between the particles and photons, including ‘virtual particles’ which are undetectable by the outside world.
Feynman diagram of an electron pair interacting via a virtual photon. Combining figures like this one corner to corner would gives a trace of the electron through the universe in one long connected path, although this would be a great oversimplification. photo credit: Papa November, on wiki commons.
Complex Feynman diagram involving the Higgs Boson. Disclaimer: I have no idea what this diagram is showing, just for a visual of what these diagrams look like. photo credit: Harp, wiki commons
The one electron universe is considered rather ‘out there’, but it does raise some interesting thoughts. The electron that is all electrons, weaving through everything from your hat to your head and all other human beings, connecting us in one big incredible masterpiece.