I am no expert on this stuff, so please forgive any errors. I've read some Feynman and seen his diagrams showing a particle and antiparticle pair getting spontaneously created, moving apart slightly, then re-combining and annihilating a moment later. The Feynman diagram expresses this as a single closed circle with opposite-facing arrows on each side. I understand this to be equivalent to a single particle moving forward in time, then reversing direction and traveling backwards in time (passing itself as its own antiparticle) back to its originating point, then turning forward in time, again and again. Can someone explain a little further about this duality, and help me understand if it is really what is happening, or if this is a sortof mathematical artifact? In other words, as far as we know, are particle-antiparticle creations and annihilations really just single particles stuck in small temporal loops, going round and round? Or is it actually two different particles that coincidentally can be described mathematically by reversing time, without any suggestion that time is actually reversing? Depending on the answers, I will be curious how this cooperates with the MWI of QM, considering the "branching" or worlds occurs only one direction in time, and would seem to breakdown when multiple branches of a single particle are attempting to make their return trip backwards in time. Thanks in advance!