What is Potential Energy, Really?

As with seemingly every other man my age, I've taken up running to stay fit. Your metabolism slows as you age and what used to come for free with youth now takes time and deliberate effort to maintain. I don't care for the running, but it needs to be done. The thing is: it does give me lots of idle time to think, just like a long walk. Both have become for me a form of meditation, a way to de-stress and to mull over complex ideas. I find that I think better when I'm moving, regardless of precisely how. Yet, near the end of every run my thoughts inevitably return to the same idea: When will this be over? I want to be done. Of course I want to complete my run, to go the distance I set for myself, but I also want, very badly, to do it in the most efficient way possible. The Optimal Route To end where you started, any route must go south for just as long as it goes north and the same goes for east and west. If you know it's three blocks west to get home and two blocks north then, because…