9. F***ing Magnets, Man, How Do They Work?
Feynman famously answered this question by essentially saying that he can't (in a much more eloquent way). Magnetism is one of the fundamental forces of the universe. On a basic level, we know that magnets work because they have opposing charges at either pole and these attract and repel one another. Okay but why does that happen? Well, all electrons have an electrical charge and in magnetic materials they all align to amplify the magnetic fields (it is the same electrical force that prevents you from putting your hand straight through a solid object, but the field extends further beyond the physical boundary of the object).
Eventually you get down to magnets as quantum objects manifesting in a classical way and things get weird. The more you try to explain how magnets work, the more deeply you have to probe into the fundamental principles of the universe. It's like when an annoying child keeps asking "why?" to everything, eventually you have to give up and say "it just is".
Understanding magnetism may seem like a pretty frivolous thing to do things like dedicate entire research laboratories to, but the day we really, truly understand how and why magnets work is the day we unlock the secrets of the universe itself.