Movie released: 1977 | Set in: 1977
|Alien contact||very low?||at any time|
Depending, of course, on whether aliens exist.
The aliens are suitably alien. They are perplexing and inscrutable, and even simple communications are difficult. They can conceal their activities at will. People greet them with a mix of curiosity and awe.
They possess baffling technologies, possibly including antigravity. And the return of people who have been gone for decades suggests that their ships can travel at least a significant fraction of the speed of light.
See: A note on aliens.