In the early 1940’s, when Feynman was still a graduate student at Princeton University , he introduced another interpretation of the nature of antimatter. In QED, Feynman noticed that antimatter traveling forward in time was indistinguishable from ordinary matter going backward in time .
This discovery allowed a totally new interpretation of antimatter. For example , if we push an electron with an electric field, it moves, say, to the left. If the electron was going backward in time, it would move to the right. However, an electron moving to the right would appear to us as an electron with positive, not negative, charge. Therefore, an electron moving backward in time is indistinguishable from antimatter moving forward in time. In other words, the electron that Carl Anderson photographed in his cosmic-ray experiments , which acted as if it had a positive charge , was actually going backward in time .
Particles moving backward in time gave a new interpretation of the Feynman diagrams. Assume that we have an electron and an antielectron colliding, releasing a burst of energy. If we reverse the arrow on the antielectron, making it go backward in time, we can reinterpret this diagram. In the new interpretation, one electron goes forward in time, releases a photon of energy, and the same electron goes backward in time .
Feynman, in fact , demonstrated that all the equations of QED were identical whether describing antimatter going forward in time or ordinary matter going backward in time. This bizarre state of affairs makes possible an outlandish theory, proposed by John Wheeler of Princeton University, that the entire universe is made of just one electron. One day, when Feynman was a student at Princeton, his adviser Wheeler excitedly claimed that he now knew why all electrons in the universe look alike. Wheeler moving proposed to explain this by assuming that all electrons look the same because they are, indeed, the same electron .
This Imagine, for example, the act of creation. Assume that out of the chaos and fire of the Big Bang came only one electron. This electron
move forward in time for billions and billions of years until it arrives at another cataclysmic event-the end of time, or Door shattering experience, in turn, reverses the direction of the electron and sends it back in time. When this same electron arrives back at the Big Bang, its direction is reversed once again. The electron is not splitting up into many electrons; it is the same electron that zigzags back and forth like a Ping Pong ball between the Big Bang and Doomsday. Now, anyone sitting between the Big Bang and Doomsday in the twentieth century will notice a large number of electrons and antielectrons. In fact, we can assume that the electron has traveled back and forth enough times to create the sum total of electros in the universe .
If this theory is true, it means that the electrons in our bodies are the same electron, the only difference being that my electrons are, say, billions of years older than your electrons. If this theory is correct, it also helps to explain a fundamental principle of chemistry: that all electrons are alike. Can Wheeler’s one- electron universe explain the existence of all matter in the universe? Can matter go backward in time and become antimatter? The answer to these questions is formally yes. But no experiment can be performed, according to
QED, that can distinguish matter going backward in time from antimatter going forward in time. Therefore, no usable information can
be sent backward in time, which eliminates the possibility of time travel. If we see antimatter floating in outer space, it may have
reached us from the future but we can’t use it to send signals to the past.