Do aliens exist?
We don’t know. Most astronomers agree that aliens probably do exist but so far we have no proof.
We can say that there are plenty of places that could support life. Everywhere we look in the Universe, we see that it's made of the same kinds of stuff, planets orbiting stars are common, water and other important requirements for life as we know it are found in all sorts of places. It certainly seems that the conditions for life are found throughout the Universe.
Of course, it's a big step from saying "aliens could exist" to "aliens do exist".
Many people claim that they do have evidence of alien life, but as yet none of it has passed the strict criteria needed to call it proof or even hard evidence. We do, however, have some “soft evidence”. This means evidence that can’t be verified but may still have some value.
Soft evidence of alien life can be roughly divided into two categories:
- Scientific (peer-reviewed studies). We don't have much of this. There have been a few interesting discoveries that could be alien in origin but most scientists are unconvinced.
- Anecdotal (stories, UFO reports, etc). This kind of evidence is often intriguing but in scientific terms, it has very limited value. We certainly can't use anecdotal evidence as proof of alien life.