According to the modern understanding of the concept of a particle, tachyon particles are too unstable to be treated as existing. Thus faster than light information transmission and causality violation with tachyons are doubly impossible
Also thanks for that little thing about theories and fiction. Up until then I believed rvolution was total fiction.
We have names for all kinds of things that don't exist, like dragons. Just because there aren't any dragons doesn't mean that the name can't exist to cover the hypothetical concept. If there was a quadrupedal green dinosaur with wings breathing fire then we'd have a name already picked out and shined up for it.
Enter the Tachyon.