Everyone knows electrons, but probably few know the One Electron Theory, a weird idea according to which every electron in the universe is actually one 10¹⁰⁵ years old particle that continually travels backward and forward through time, possibly 10⁸⁰ times.
The theory was first thought up by John Archibald Wheeler, a theoretical physicist who worked on the hydrogen bomb at Los Alamos and later taught at Princeton. He is largely known for reviving interest in general relativity in the 1940s and 1950s.
One of the biggest reasons that this thought experiment was proposed by Wheeler is that each and every electron looks exactly the same. They all have the same mass and the same electric charge.
Proposing that the entire universe contains just one electron may not seem all that absurd, when we consider that the only change would be to the idea of what an electron is. In practicality, everything would still function the same.
According to the theory, in the same way as an electron can be bounced around in space when hit with light, the electron might also be able to bounce backward in time. The consequence of this is that electrons moving backwards in time are positrons, the antimatter component of electrons. So, not only are all electrons the same electron, but all positrons are also the same electron moving backward.
It is estimated that there are roughly 10⁸⁰ atoms in the universe. If we ignore the fact that many atoms have more than one electron, we can simplify the number of electrons in the universe as around 10⁸⁰.
Although electrons are treated as stable for theoretical purposes, the experimental lower bound for the electron's mean lifetime is often given as 6.6×10²⁸ years. Using this, we can get an idea of how this theory actually plays out.
The theory and these numbers imply that the one electron in existence has traveled through the universe 10⁸⁰ times, each time taking 460 septillion years. We can double these numbers for each time that the electron had to go back through time, which equates to the one electron in the One Electron Theory being 10¹⁰⁵ years old.