Entertaining and thought-provoking as this was, it seems like it's worth having a discussion among practicing physicist popularizers about what we'd like everyone to know about physics. (For the pedants in the audience, by "everyone" I'm not including very young children, and remember, this is aspirational. It's what we'd like people to know, not what we actually expect people to know.) I'm still thinking about this, but here are some basic ingredients that make the list, including some framing topics about science overall.
- Science is a reason- and logic-based way to look at the natural world; part of science is figuring out "models" (ways of describing the natural world and how it works) that have explanatory (retrodictive) and predictive power.
- Basic science is about figuring out how the world works - figuring out the "rules of the game". Engineering is about using that knowledge to achieve some practical goal. The line is very blurry; lots of scientists are motivated by and think about eventual applications.
- Different branches of science deal with different levels of complexity and have their own vocabularies. When trying to answer a scientific question, it's important to use the appropriate level of complexity and the right vocabulary. You wouldn't try to describe how a bicycle works by starting with the molecular composition of the grease on the chain....
- Physics in particular uses mathematics as its language and a tool. You can develop good intuition for how physics works, but to make quantitative predictions, you need math.
- Ultimately, observation and experiment are the arbiters of whether a scientific model/theory is right and wrong, scientifically. "Right" means "agrees with observation/experiment whenever checked", "wrong" means "predicts results at odds with reality". Usually this means the model/theory needs an additional correction, or has only a limited range of applicability. (Our commonplace understanding of how bicycles work doesn't do so well at speeds of thousands of miles an hour. That doesn't mean we don't understand how bikes work at low speeds; it means that additional effects have to be considered at very high speeds.)
- There are many branches of physics - it's not all particle physics and astrophysics, despite the impression you might get from TV or movies.
- Physics explains light in all its forms (the microwaves that heat your food; the radio waves that carry your wifi and cell phone traffic; the light you see with your eye and which carries your internet data over fibers; the x-rays that can go through your skin; and the really high energy gamma rays that do not, in fact, turn you into an enormous green ragemonster).
- Physics includes not just looking at the tiniest building blocks of matter, but also understanding what happens when those building blocks come together in very large numbers - it can explain that diamond is hard and transparent, how/why water freezes and boils, and how little pieces of silicon in your computer can be used to switch electric current. Physics provides a foundation for chemistry and biology, but in those fields often it makes much more sense to use chemistry and biology vocabulary and models.
- Quantum mechanics can be unintuitive and weird, but that doesn't mean it's magic, and it doesn't mean that everything we don't understand (e.g., consciousness) is deeply connected to quantum physics. Quantum is often most important at small scales, like at the level of individual atoms and molecules. That's one reason it can seem weird - your everyday world is much larger.
- Relativity can also be unintuitive and weird - that's because it's most important at speeds near the speed of light, and again those are far from your everyday experience.
- We actually understand a heck of a lot of physics, and that's directly responsible for our enormous technological progress in the last hundred and fifty years.
- Physicists enjoy being creative and speculative, but good and honest ones are careful to point out when they're hand waving or being fanciful.