I learned a lot of things from Professor Hanna in my Astrophysics class, this being one of them. I’ve already given away the punch line, but for those who aren’t familiar with it:
A farmer is having trouble with a cow whose milk has gone sour. He asks three scientists—a biologist, a chemist, and a physicist—to help him. The biologist figures the cow must be sick or have some kind of infection, but none of the antibiotics he gives the cow work. Then, the chemist supposes that there must be a chemical imbalance affecting the production of milk, but none of the solutions he proposes do any good either. Finally, the physicist comes in and says, “First, we assume a spherical cow…”
Physicists use the phrase to poke fun at themselves for all the simplifications we tend to make. Another McGill prof, Cliff Burgess, was heard to say, “Life is either a free particle or a harmonic oscillator,” and I think most physics students would believe it, even though most things in everyday life are neither free particles nor harmonic oscillators. What does everyday life have to do with physics, anyway?
But it’s not all crazy talk, for I did see a spherical cow yesterday. Metaphorically at least. I’ve heard it said a couple times that many things, even non-fluidic things, can be modelled as fluids. In particular, people, physically speaking, behave like fluids. Not an obvious jump, sure, but it works.
I was coming down to the Milton gates just past 17h, when the majority of people are walking home through the ghetto. The light changed from red to green and a massive hoard of people surged ahead to cross Rue University, each one darting around obstacles and jostling for a position among the other pedestrians. On one side of the corner a stream of people splashed onto a car turning right, some people being diverted away from Milton and up University, others flowing down the middle of Milton. As people spread down the street they spread out, the pressure that had built up at the stop light releasing. Faster people passed others on the inside by skipping along the curb or going into the street, while the average paced people were buffered from the buildings by the occasional group of people who had stopped at the side to talk, mimicking the way water moves down a pipe. We were all just molecules in the same fluid.