Stephen Hawking absolutely believed in the existence of these beings and warned against contacting them for fear that they would view humans as some sort of subhuman life useable only for food.
Christians who take the Word of God seriously know that as these are the last days, these beings are not extraterrestrials but fallen angels and demons serving the Will of God.
The US Navy has already told us there is something there, there with the release of the USS Nimitz/USS Roosevelt videos. They never mentioned aliens but simply said this is unidentifiable and it clearly did things which would kill a human pilot. Are they extraterrestria, inter-dimensional, who knows but we have been told something is there.