Tachyon

A tachyon is a hypothetical elementary particle that is presumed to go faster than the speed of light! Because of that, any tachyon will have to travel back in time.

As a normal particle approaches the speed of light, time slows down drastically for it. Because time simply stopping for something that time was relevant to before would break some physics laws and be absurd, any normal particle that has mass(or structure made up of many particles) can never actually get to the speed of light. It can go as close as it wants, but light will ALWAYS win the race, given a long enough time. Well, even if you did go so so close to the speed of light, the term “race” (along with almost every other term) will lose its meaning. Specifically, the race against light. Sure, we have measured light’s “speed”, but this is just used for standard classical physics. Light actually has no speed. For a photon (light particle), time is completely motionless. In other words, there is no time for a photon, because it is traveling at the speed of light. Anything that is massless (like a photon) travels at the speed of light, always and forever. Things that have mass have more control over their speed, being able to speed up and slow down, but still stay in the range of this: speed<c, where “c” is the speed of light.

For tachyons (if they exist), things get even weirder. First of all, a tachyon has control of its speed, similar to normal things. It can move faster and slower. But, since it always moves faster than the speed of light (similar to how we always move slower), it moves BACKWARDS in time. You might just be thinking here, “????”, or you could also be thinking “Time machine!!”. We could not really make a Time Machine out of them, because we would have to “catch” them from the future, and we don’t know how to do that, because they’ll just continue moving into the past, or could we? If you or me continue thinking about this, we’ll probably have a seizure or a stroke, or probably die.

I’m ignoring my own warning. Since tachyons go backwards in time, they MIGHT be able to be used for a time machine. But you have to be careful. Your time machine must go REALLY fast. Why is this important?

DO NOT go super fast in your time machine (in motion) while you’re going back in time. When you want to go back forward, turn on “hyper speed”, very close to the speed of light, and do a few loops around Earth, Mars, and the Sun. Then, when the physics tells you that if you continue you’ll be too far in the future, you go slower and come back to earth, where time will be restored and in sync.