My favorite memories of college are being exposed to combinations of exciting ideas. I attended a large university. It's the kind of place crawling with grad students, each tackling a potentially rewarding research problem in their their own highly specialized area of study. It's the kind of magical place where an architect might study alongside a mathematician in statistics class, or a molecular biologist might compare notes with a mechanical engineer.

It was one afternoon when a classmate and I were approaching our lecture hall after leaving the shuttle bus. The hall stood on top of a hill, and we still had a respectable climb before reaching class. We had been chit-chatting on a less memorable subject when I made the mistake of talking shop.

“Ugh. Look at all that potential energy we've got to store.”

My friend replied quickly, in a confused and slightly defensive tone. “What do you mean?”

“I mean, look at how far we've climbed. We've stored all this potential energy after climbing up this far.”
“Are you sure? I don't think that's how it works.”
“Yeah, remember from physics class? When you increase your elevation your potential energy increases.”
“Well, maybe in physics class, but you're not really gaining any energy. I mean, how can a person gain energy by climbing a hill?”
“OK, I'll be more precise. You're not really gaining any energy. The energy is already stored within your body chemically before you need it, and your muscles convert it into motion which pushes you up a hill.”
“No way, man. You don't charge with energy when climbing a hill.”
“Sure you do. You will have greater energy when you are at the top of a hill compared to when you're at the bottom.”
“I don't think you understood that lesson, potential energy isn't really related to climbing a hill.”

A wiser person may have dismissed this difference in opinion and carried on with a less esoteric topic. However, I had spent more time with my nose in books than practicing polite conversation. My days worth of calculations and reports outweighed the few hours of conversation. To my ears, this was an assertion that people were somehow exempted from an essential rule of physics. It bordered on defamation. I had to resist this challenge to my dogma.

“No, I'm certain that it still applies. Since your elevation at the top of the hill is greater than at the bottom, your potential energy will have increased.”
“Are you sure? Then where does the energy go when you walk back down?”
“The energy is dissipated as heat. There will be an increase in temperature, probably in your legs. They do all the work getting you up the hill. They're the only part that moves as you walk back down.”
“No, I don't think that's right. You would burn up. See, that just shows that it's not actually real, its just an imaginary method used for calculations.”
“You don't believe me? Here's another example. Imagine you're parked in your car at the top of a hill.”
“Now push the car and start it rolling down the hill. It starts moving, right?”
“The potential energy is being converted into kinetic energy, or motion. See?”
“OK, OK But you're talking about cars, I don't think people can really gain potential energy.”
“Sure they can. These physical laws still apply to people, since we have mass and can change elevation.”
“Yeah, but people don't have wheels, and they can't slide around like the blocks that appear in those physics puzzles. We have legs instead.”
“That doesn't really change the potential energy of the overall system. A person can still be considered as an independent object which has mass and can change elevation on an inclined surface.”
“No, man. I think you missed the point of the lesson.”

This went on a bit further until the class demanded our attention, and the matter was left undecided. I am grateful for my lack of focus, since I rapidly forgot the argument and cooled down quickly. Still, climbing a hill or staircase can sometimes bring back pleasant memories.

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