Antimatter

Discussion

Every particle has its own antiparticle. Two major discoveries helped physicists to establish this fundamental principle:

  1. positron (e+)
    1931
    Examining cosmic-ray data, Anderson discovers the positively charged electron later named the positron. He receives the 1936 Nobel Prize.
  2. antiproton (p)
    1955
    Using an accelerator at Berkeley University, Segre and Chamberlain discover the antiproton. They receive the 1959 Nobel Prize. (Later, physicists learn that a proton contains quarks and an antiproton consists of antiquarks.)

pair production

annihilation

interesting (but wrong) idea

As a by-product of this same view, I received a telephone call one day at the graduate college at Princeton from Professor Wheeler, in which he said, "Feynman, I know why all electrons have the same charge and the same mass" "Why?" "Because, they are all the same electron!" And, then he explained on the telephone, "suppose that the world lines which we were ordinarily considering before in time and space — instead of only going up in time were a tremendous knot, and then, when we cut through the knot, by the plane corresponding to a fixed time, we would see many, many world lines and that would represent many electrons, except for one thing. If in one section this is an ordinary electron world line, in the section in which it reversed itself and is coming back from the future we have the wrong sign to the proper time — to the proper four velocities — and that's equivalent to changing the sign of the charge, and, therefore, that part of a path would act like a positron." "But, Professor", I said, "there aren't as many positrons as electrons." "Well, maybe they are hidden in the protons or something", he said. I did not take the idea that all the electrons were the same one from him as seriously as I took the observation that positrons could simply be represented as electrons going from the future to the past in a back section of their world lines. That, I stole!

Richard Feynman, 1965