Earlier quoted context omitted.
Briefly put: the speed of light. It takes a long, long time to get anywhere, because light moves at a relative crawl compared to the distances between stars, so it would be a long and energy-intensive process to visit another planet, especially given how hard it would be to detect a civilization there before you departed. The Earth didn't emit much of a signal on radio waves until about 1900, so even if the aliens we…
The speed of light is a constant but we are still very behind in terms of understanding the universe and physics, we still do not have a unified theory which bridges general relativity to quantum mechanics. We know next to nothing about dark matter(haven't found any yet), also in terms of energy production we have not achieved - room temperature superconducting and fusion reactors. We can barely get rockets outside o…
1) FTL implies CTCs, that means paradoxes. How are those going to be resolved? Because the Cosmic Censor stuff never quite makes sense -- exactly what mechanism is going to forbid you from opening the message that says, "Do not send this message back in time?"
2) Again allowing for FTL ... where are the self-replicating machines spreading across the cosmos? Pop to another star system, pop to another galaxy, or even a local cluster. They should have already been there. The universe is vast. Most species will realize that this is a terrible ass idea, but there's always a lunatic in a large enough crowd, and it'll be a pretty large crowd.
Nobody ever deals with these points. People want FTL to be true because, well, Star Trek (or Star Wars, or Farscape, take your pick). It's a bit dull, plodding along at some small fraction of c, but the universe doesn't have to be exciting for us. And I'm not going to bet otherwise.