Good points about the moon. It would be sad, at least for me, if we were the only intelligent life in the universe. I think it is one of those things that is hard to disprove since we can't possibly investigate or even know about every habitable planet. Odds only go so far. I am holding out hope!
I am too!
If we exist, then why not others too?
Every time I look up at the starry sky I think about it. All those millions and MILLIONS of stars up there, most of them we cannot even see. Many of those stars probably have a solar system attached to them. It seems to me the chances are quite high at least some of those planets would have life on them. Even intelligent life in some cases. During our history, there have been so many things we thought we knew, only to prove ourselves wrong later on in time. I think these mathematical calculations will probably be reworked someday and found to be incorrect.
Also, I think space goes on forever. There is no big brick wall out there with the words "The end of the universe" painted on a sign. And even if there was a big brick wall, or some sort of "end", what is on the other side? If the universe is sphere shaped as some suggest, what is on the outside of the sphere? And if space extends outwards forever, we cannot even begin to understand how many stars and planets actually exist. New stars and planets are created all the time. The light we see from most of those stars was emitted thousands of years ago and is just now reaching us. Most of us have problems comprehending this because we have difficulty understanding the concept of eternity and endlessness. But this doesn't mean it doesn't exist, it just means that human beings have not evolved enough to wrap our minds about something so vast, huge and endless.