The intelligent alien debate
Our universe is 14 billion years old. The Milky Way galaxy is 13.61 billion years old. The Solar System is 4.571 billion years. The Earth is 4.543 billion years old.
The scope for fundamentally different life is infinite given time, environment, gases and various other factors such as DNA / RNA etc. Anything not from Earth is extremely unlikely to be able to breed with human beings from Earth. Having some substances in common with life not from Earth hardly makes such life our brother
If you are defining 'alien' as being one person compared with another then that is a crass use of language. When you and me converse about aliens it is about life not emanating from Earth.
In order that you cannot mistake my fundamental beliefs on the matter here they are. There may be no intelligent alien life anywhere except on Earth. There may be millions of intelligent alien civilisations. Even if there are millions of intelligent alien civilisations they may be so far apart that even with the ultimate in advanced technology none of them will even detect that any others exist.
So your "You don't believe in aliens" does not work. I merely believe that there is no proof that intelligent aliens have been to Earth or in its skies or above Earth in space. Indeed there has been no detection of any proxies for intelligent life anywhere other than on Earth. I would welcome such detection. But anyone who believes that he / she has evidence / proof should deliver it to be scientifically tested. A lot of would-be provers that alien life has been or is on Earth tend to not submit such alleged evidence / proof for scientific analysis. Their excuses for not doing this are legion, even attacking such fundamental science. They want to 'milk' their story, rather than have it legitimately annulled.