This is Richard Feynman's take on a simple question, why do magnets repel each other?

A little more on Richard Feynman. He was an American theoretical physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics for which he proposed the parton model.

As always: A scientist is not a person who gives the right answers, but one who asks the right questions. ...

What sets Homo sapiens apart from other animals? Among other things, our chins do. That piece of bone sticking out from your jaw is somewhat of a mystery - one that's inspired a diversity of wild theories to explain its purpose, according to a paper published this month in Evolutionary Anthropology.

The author of the paper dismisses a number of these explanations, such as the possibility that the chin serves as a sexual signal (such traits usually only appear in one sex - like the mane of a male lion). Another proposal is that the chin acts to protect your throat - an idea the paper's author also shoots down, because for this to be a substantial advantage, humans would have to be constantly punching each other in the face.

So the mystery rem ...