The winning team has momentum going into the playoffs. The political candidate is trailing in the polls, but has the momentum. The momentum of the stock market can make people worried or hopeful.
Everything we think about in the world, from gambling to politics, is affected by the metaphor of momentum. But the idea of momentum—the tendency of a body moving in a direction to continue moving in that direction—has not always been around. It’s so intuitive, so obvious, that it’s hard to imagine a world where the idea didn’t exist. But the fact is, for thousands of years people didn’t have any concept of momentum.
If they didn’t believe in momentum, what did they believe?
Aristotle thought that an object could only move as long as a physical mover was in contact with it. Thus, he believed that when you throw a rock, you move both the rock and the air around it… and the rock only continues to move after it leaves your hand because the disturbance in the air carries it forward.
Avicennan and Buridan, in the middle ages, believed that the action of throwing the stone injected a property, like a substance, into the rock, called “impetus” or “inclination” (mayl). There was much debate over whether this substance was pushed back out of the rock by the air, or dissipated naturally over time.
It was not until the 17th century that we got the idea of momentum being a property inherent in objects themselves, and the idea that “momentum” could equally be applied to bodies at motion or at rest.
Why should anyone care about all of this ancient history?
Imagine living in a world where the notion of momentum didn’t exist. It wouldn’t just affect the way you view physics… it would affect the metaphors you use to think about everything in your life. How would it affect your day-to-day life if you did notbelieve in “momentum”?
Here’s another thought for you: Just as Aristotilean physics was wrong, there are many things in our current ideas about physics that we will probably discover to be wrong one hundred, or one thousand, years in the future. There will (likely as not) be people sitting around absolutely astounded at what those crazy Ancients believed way back when they referred to the date as “2000 C.E.”
We have no idea what the view of the universe will be in 1000 years, but it can be fun to turn on your “science fiction imagination” for a moment. Our ideas of the “basic building blocks” of the universe has evolved from tiny geometric shapes (Greek atoms), to tiny billiard balls with even smaller billiard balls orbiting around them (Bohr’s atoms), to tiny billiard balls with weird clouds of energy waves around them (Schrödinger’s atoms), to an even stranger ball of multi-dimensional strings and vibrations (String theory). What will the theory be in 1000 years? Atoms are the intersection of color-like fields that mix together in a 20-dimensional space? Atoms are a projection of a population of Property Points from higher dimensions onto our universe? Atoms are an illusion created by our nervous systems because of the way our senses interact with a continuous energy field of the universe?
It’s silly to speculate, but it drives home a serious point: Scientific knowledge doesn’t reveal the structure of the universe. Scientific knowledge reveals the best metaphors that we have come up with—so far—to understand our experiences. These metaphors are not “right”. They will never be “right”, because they are just a lense through with we understand things.
It should be humbling to see the universe through this kind of lense, and give pause to anyone who ever says, “I know that THIS is the way things are.”