On the left, a clockwise-rotating particle moves forward in time. It turns abruptly in direction, emitting a photon burst. It then proceeds backward in time.
On the right, the same phenomenon is witnessed in normal time. A clockwise-rotating particle and a counter-clockwise-rotating particle (eg., an anti-particle) converge together in mutual annihilation, evaporating in a photon burst.
As extraordinary as it sounds, this is the belief held by many theoretical physicists. Nobel Laureate Richard Feynman proposed this startling hypothesis using his famous Feynman diagrams, represented here. An anti-particle is actually a particle moving backward in time. The same particle exists in two different time zones.