Physics is a lie?!

by Bradley Knockel

You have learned or will learn so much in this class, but nothing you have learned or will learn is exactly true! Saying that it's a lie would be an exaggeration, but it is important to understand the limits of what you understand.

Nothing I teach is exactly correct. It is all an approximation. When hitting a baseball, it will not land where we calculate for many reasons: air resistance, curvature of the Earth under the ball's trajectory, gravity being weaker at the top of the trajectory, pull of gravity from the Moon, and the fact that gravity is actually the result of curved spacetime and is not a force at all. If you take more physics classes, you build and improve upon what you know until you get to the best truth we have: general relativity and quantum mechanics. But we can't start there or you wouldn't understand it. Imagine being told about curved spacetime (and the math called differential geometry needed to describe it) and the quantum wave equation for particles (and the math called complex numbers and linear algebra) on your first day of class. Even then, after a week of calculations where the ball will land, a gust of wind blows the ball far away from what was predicted. With all this said, on a day without wind and if hitting the ball softly enough to prevent air resistance from being significant, your predictions made using your introductory physics will be very good.

You only understand the type of physics related to the types of problems we've been doing. If the topic ventures too far from what you've seen in class, you probably don't yet know the physics needed to think about the situation. The real world is much more complex than the simple problems we give you. When you leave school, the physics from this class is not enough to describe most things you may encounter, but it's a very good and necessary start. In fact, well-paying jobs in the real world typically involve that you learn things very different from physics, but you will need to grow your understanding of something, and learning how to understand new things is a valuable skill that a physics class will teach you. Physics also teaches us how to apply things we already know to new situations and to make connections between the new and the old. Learning how to keep taking the next step towards being more correct is a life skill that helps all of us, especially scientists whose job is to keep improving our understanding!