Apparently, this is a well-known thing in the military, but no one told me until we learned about it in the film Beneath Hill 60. It's also a potential reason why pirates are known to wear eye patches—from popping up and down between decks—though it's rather hard to be sure. But I think the primary use case is going for a pee in the night.

Shut one eye to keep your night vision

Learned from Joe Smith’s short entertaining TED talk: How to use a paper towel.

Dry your hands with only one towel

Apparently it’s called the photic sneeze. I asked the question of Focus magazine in the UK and it seemed to me that Science doesn’t really know why. We need to find out.

Bright light will free your sneeze