Desperately encountering the light barrier
Rebellious idea of particles faster than light has naturally arose with the knowledge of the special role of the speed of light as a limit up to which anything massive could be accelerated in our world, spending a lot of energy though, more and more as we approach that limit. We are told so by formulas of the theory of relativity, and there is no convincing reason to doubt its validity. It follows from those formulas that if a particle moves faster than light, its mass squared must be negative. This is quite unusual yet acceptable because such a particle could not be weighted anyway because to do so, this must be stopped while it would take an infinite amount of energy just to reduce its speed to that of light. Thus, it turns out that such particles must always be in rapid motion, so they are named tachyons — swifts in Greek. A thought experiment on registration of tachyons leads to a cause-and-effect contradiction referred to as the tachyonic antitelephone: tachyons arrive at the detector before they are emitted from the source. That is why it is considered that tachyons cannot appear in our world while several experiments on their searches have been held nonetheless.