Paradoxial Computer - Tachyons

This was not written by me, but a friend at another board. My knowledge on the subject is very limited. From what I understand, which may be wrong, you can not travel back in time as it would violate causality. Is what he is describing possible? I understand anything with rest mass can never go faster then c, and if you could time would stop, the universe would be seen as a infinitesimal point. And you would be at every point is space simultaneously. But I think I remember reading here that if you could go faster then c you would go backwards in time. As nothing can go at c, but going faster is possible. So if tachyons do exist does time go backwards for them? And if so would it ever be possible use them in a controled manner?

Here is what was posted at the other board:

It is true that nothing with rest mass can travel at or above light speed. In addition to the reasons you posted add that you would have infinite mass upon reaching light speed (hence there is not enough energy in the entire universe to get you there as you’d need infinite energy).

However, if for fun you speculate on travelling faster than c then the math insists that time move backwards for the traveller.

Tachyons are only a theoretical particle at this point and have never been obeserved. Physics can speculate on them but I think few physicists believe such a creature exists. If it did one implication is that the tachyon can never go slower than light speed. How you would handle such a thing is beyond me. You might generate them (if they exist) but using them opens you to paradoxes as you can now violate causality.

Once upon a time people thought if you sailed too far from shore you would fall off the end of the world. Once upon a time people thought that no person would ever set foot on the moon.

Imagine what would happen if everyone thought along accepted norms. We need the freaks out there thinking of the “impossible”. Otherwise I might not be able to have my VR helmet and 5000 naked women TV channel universe someday. :slight_smile:

If you have an object going faster than light from point A to point B in one inertial reference frame, then there will be other frames where the object is simultaneously at A and B, and still other frames where it’s at point B before it is at point A.