In the first half of this video, Bill Stone discusses his experiences caving and how lonely it is being three kms underground, surrounded by dark rock.

The thought of it freaks me out. I am somewhere in between a claustrophobic and an agoraphobic, I get mild anxiety being too far from civilisation (perhaps bright city lights) so a cave is not my ideal hideout.

The thought of space travel has always struck me in the same way. It’s so dark out there and so isolated – in all its tremendous infinity.

Do you think you’d feel trapped in space?