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Why Antiparticles Must Exist in Nature
Why Combining Quantum Mechanics and Relativity Make the Existence of Antiparticles Inevitable
In the following, I will argue (following Feynman) that two conditions are needed for antiparticles to exist in Nature: the first is that the energy of a particle is always positive, and the second is that Nature obeys the principles of relativity.
A Bird’s-Eye View of Spacetime Diagrams
In order to fully grasp the conclusion of this article, an explanation of the geometric properties of spacetime diagrams (or Minkowski diagram) is needed. Spacetime diagrams are graphical representations of the motion of particles in spacetime.
To better understand the possible types of intervals in a spacetime diagram, it is better to use only two dimensions, one time dimension (vertical axis) and one spatial dimension (horizontal axis), as shown in Figure 2. The trajectory of an observer on a diagram is called a world line.
