Just a small "joke" about higher-than-speed-of-light travelling. If you take the equation of mass
m = m0 / sqrt(1 - v^2 / c^2)
and you assume that there is a particle with imaginary mass m0 (the square of mass is negative), then for this particle the speed of light will be the MINIMUM speed, the maximum speed will be unlimited, the mass will decrease when increasing the speed going to zero when speed goes to infinity.
This "joke" is mathematically correct, and in physics it is called "tachyon". Ths problem is that if such particle can interact with our matter, the principle of causality is violetad - such particle could send information to its past that could change its future. As I know, this problem is not resolved yet.