I understand the need for 'The Line'. Without it we would branch out into Science Fiction without studying the facts. So I concede that in the present tense nothing moves faster then light in a vacuum.
Seeing as how faster then light travel is not permitted by Einsteins Theory of Relativity the only way another form of intelligence life could get here was either by developing at a faster rate then us or by bending time/space. Perpetual Motion is ruled out as it goes against the Conservation of Energy rule. So where does the power come from to get them from point A to point B?
Second if intelligent life has been visiting us then why are they so secretive? They would have the power to destroy us if need be. Why not say hello?