"Just a rule for reactions" drives quite a lot of physics. Conservation rules are how to describe all of the things that do not happen: why a hammer doesn't va

"Just a rule for reactions" drives quite a lot of physics. Conservation rules are how to describe all of the things that do not happen: why a hammer doesn't vanish, why all of your electrons do not turn into positrons, and so forth. That's what is so fascinating ... you have this odd topological boundary and it creates a violation in known rules.