As a science teacher, I've always enjoyed teaching students how dark true black really is. I take a large cardboard box, poke a small hole in the middle of it,

As a science teacher, I've always enjoyed teaching students how dark true black really is. I take a large cardboard box, poke a small hole in the middle of it, and have students hold other "black" objects next to the hole. Students are pretty consistently amazed to see the difference, if they have never noticed the phenomenon before on their own. I would love to see this material in person.