[nyrath]

http://www.projectrho.com/rocket/fasterlight.php#id--Causali... "Causality, Relativity, FTL travel: chose any two. You cannot have all three."

Physicists choose Relativity since it has been tested to many decimal places and always comes through with flying colors. Relativity means that FTL travel is the exact same thing as a time machine. Time machines can cause temporal paradoxes like the Grandfather paradox. Temporal paradoxes render Causality impossible. And without Causality, the entire structure of science crumbles.

The only way to have all three is if there is some weird magic law that makes it impossible to use time machines to create temporal paradoxes.