https://en.wikipedia.org/wiki/Faster-than-light#Superluminal_communication https://en.wikipedia.org/wiki/Faster-than-light#Superluminal... "Faster-than-light c

https://en.wikipedia.org/wiki/Faster-than-light#Superluminal_communication https://en.wikipedia.org/wiki/Faster-than-light#Superluminal... "Faster-than-light communication is, by Einstein's theory of relativity, equivalent to time travel. According to Einstein's theory of special relativity, what we measure as the speed of light in a vacuum (or near vacuum) is actually the fundamental physical constant c. This means that all inertial observers, regardless of their relative velocity, will always measure zero-mass particles such as photons traveling at c in a vacuum."