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. 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