Is There a Particle That Can Travel Back in Time?

Yes, there is a hypothetical particle, called the tachyon, that could travel back in time. One catch: It almost certainly doesn’t exist. Time and Speed of Light Before we start talking about time travel, we first must talk about the speed of light. All objects in our universe are constrained to go no faster than the speed of light. The only particles capable of achieving light speed are massless particles, like light itself. Anything with even a tiny amount of mass will find it impossible