It's antiparticle only moves forward. There is only one particle in the entire universe, racing forward and back, reversing polarity when reaching either end, and returning. Everything in the universe is made of this one particle, taking its place for the briefest of instances, before flying off to be part of something else in the past or future. The one particle is quadrillions of quadrillions of times older than time itself, because it is everything, and everything is composed of it, one particle/instance at a time.

And boy, is that particle tired!