Feynman on Explaining Physics

Here’s a video of physicist Richard Feynman describing why it can be problematic to use physics to “explain” phenomena. It takes him a while to get to the point he’s trying to make, but I recommend that you stick around until the end.

The goal of physics is to answer “why” at deeper and deeper levels. Some of my favourite moments as a teacher have been ones where a student has continued to ask me why something is the case, and I keep answering until together we reach the horizon of our current knowledge about the universe. Why does matter resist acceleration? Why does time flow forwards but never back? We may never know, but we can keep digging — at least until we’ve found what seems to be a truth that lacks any possible explanation for why it is true.

0.2 Thinking Like A Physicist

Critical Questions:

  • What does it take to really understand physics?

The crucial problem in teaching physics is that most people have a certain understanding of physical principles before they ever approach the subject in a classroom or book. The reason this is a problem rather than a benefit is that the average person’s understanding of physics is wrong.

To be more specific, there are two kinds of “understanding” one can have about physics. The first is the one that babies slowly gain as they teeter precariously on their pudgy little legs and try to manipulate solid objects with their hands and, occasionally, mouths. This is baby science in action: after a few hundreds trials, even an infant’s brain knows that if you push an object to the right, it will generally move in that direction.

"Baby Mum-Mum" by Joe Shlabotnik on Flickr
Experiment #745: Put Thing In Mouth. Results: Inconclusive.

By the time we’ve grown up, this understanding has solidified into that intuitive, unconscious awareness of the relationship between cause and effect which allows us to catch baseballs, flip pancakes, or juggle chainsaws.


0.1 Welcome

quark structure
The Secret Lives of Protons: Two up quarks and one down quark.

One day, when I was in high school, my chemistry teacher began a lesson about subatomic particles.

“You know those electrons and protons you’ve been hearing about the last few years?” she asked.

“Yes,” we students dutifully replied.

“You know how all of your teachers have always said that they’re the smallest things we know of?”

“Definitely,” we answered.

“And you know how you’ve always been told that they’re the fundamental building blocks of matter — that it’s impossible to break them apart into component bits?”

“Of course!” we scoffed — although nervously, because already we could sense that perhaps we had been misled.

“Well,” said my teacher, “it turns out that protons are in fact made up of even smaller particles called ‘quarks’. And that’s what we’re going to learn about today.”

Needless to say, I was outraged. I felt like a kid hearing that Santa Claus doesn’t really exist. What were they going to tell me next? What other lies had I been swallowing in school? Was two plus two ever really four? Were sentences that ended with a preposition really that big of a problem?