Some people believe in UFOs – unidentified flying objects that carry alien visitors. But there is no confirmed scientific evidence.

People (including scientists) do not always tell the truth (including to themselves) and sightings by single individuals or groups are not accepted as reliable evidence. All observations must be ‘replicated’.

Photographs and even radar images can be deceptive, deliberately or not.

However, aliens exist in our imaginations and stories.

An internet list of alien species has several hundred entries, and does not cover every science fiction book that has ever been written. Vogons are an example of species whose attention we might not want to attract. There are plenty more.

You can watch a programme on ‘alien evolution’.

What difference would it make?