There's also the very real possibility that we are the only intelligent life in the universe. To people who say that's unlikely, there is at present absolutely zero scientific evidence that there is any other life out there. You can come up with ad hoc explanations why we just haven't seen them, but the actual evidence is that there's none. The argument, "But the universe is so big, there just MUST be aliens out there somewhere", that's like saying, "The Pacific north west is so big, there just MUST be a Bigfoot out there somewhere", or "The Atlantic Ocean is so big, there just MUST be Atlantis under there somewhere." That's not how science or probability works. And if there are no aliens, then all this work is a waste of time and money.
There's also the very real possibility that we are the only intelligent life in the universe. To people who say that's unlikely, there is at present absolutely zero scientific evidence that there is any other life out there. You can come up with ad hoc explanations why we just haven't seen them, but the actual evidence is that there's none. The argument, "But the universe is so big, there just MUST be aliens out there somewhere", that's like saying, "The Pacific north west is so big, there just MUST be a Bigfoot out there somewhere", or "The Atlantic Ocean is so big, there just MUST be Atlantis under there somewhere." That's not how science or probability works. And if there are no aliens, then all this work is a waste of time and money.