>They've always been here.
Then they are neither alien nor extraterrestrial.
>night would be as bright as day.
If the universe is endless and uniformly populated with luminous stars, then every line of sight must eventually terminate at the surface of a star. Hence, contrary to observation, this argument implies that the night sky should everywhere be bright, with no dark spaces between the stars.
https://www.britannica.com/science/Olbers-paradox