13 October

If you wear glasses, and don't have them with you, looking through a tiny aperture can sharpen what you're seeing pretty significantly. You can do it with your hand (as in the pic), or use anything that will give you a small hole to look through, like a pinhole in a piece of paper. There are explanations for why this works, though not entirely convincing ones to me. Vision is one of those things where I think most of the science is completely bonkers.