# Does a Particle / Antiparticle become the Same Particle as their Speed Increases to the Speed of Light?

Facts:

• A Photon travels at the speed of light.
• A Photon is its own Antiparticle.
• An Particle Travelling back in time (e.g. an Electron) is its own Antiparticle (i.e. a Positron).

My question is: Because a Photon travels at the speed of light (where time slows down) and is therefore its own antiparticle. Does this hold true for other Particles e.g. an Electron, travelling at the speed of light. If so, Why? If not, Why?