Sean Carroll wants you to talk about physics like a baseball game

The following is an excerpt from The Biggest Ideas in the Universe: Space, Time and Motion couple Sean Carroll.

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My dream is to live in a world where most people have educated opinions and passionate opinions about modern physics. Where you hit it off after a hard day’s work, hit the pub with friends and chat about your favorite dark matter candidate or competing interpretations of quantum mechanics. A world where, as children run to a birthday party, one parent says, “I don’t see why anyone thinks there should be any new particles near the electroweak scale,” and another immediately responds, “So how the hell are you going to fix the pecking order?” After all, people have opinions about supply-side economics or critical race theory. Why not inflationary cosmology and superstring theory?

That’s not quite the world we live in. Even more than most other academic disciplines, physics is a field by and for specialists. Practitioners speak to each other in highly specialized jargon, dominated by mathematical concepts most people have never heard of, let alone mastered. There are sensible reasons why this is the case, but it doesn’t have to be. This situation is largely due to the way physicists tend to share their knowledge with the rest of the world.

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If you are not an expert and want to learn more about modern physics, you basically have two options. One is to stay at a popular level of explanation, where you can learn more about some of the relevant concepts without digging into technical or mathematical details. You can read books, attend lectures, watch videos, listen to podcasts. The good news is that we have a vibrant ecosystem of such resources and it is possible to learn a lot from them, albeit somewhat randomly. But in the end, you know you’re not getting the real stuff. What you get are images and metaphors, rough translations of the underlying mathematical essence into ordinary language. You can cover an impressive distance on this route, but something vital will always be missing.

The other route is to become a physics student. It could literally be at a university or by putting together the right textbooks and resources online. Along the way, you will have to master a lot of mathematics: calculus and differential equations especially, but also aspects of vector analysis, complex numbers, linear algebra, etc. The journey will be rewarding, but frustratingly slow. It usually takes at least a year of introductory courses before a student hears about relativity or quantum mechanics. And most physics students can earn an undergraduate degree — or even go all the way to a doctorate — without learning particle physics, black holes, or cosmology. These goodies are reserved only for specialists in particular sub-fields.

The gap between learning physics as an interested hobbyist, relying on obscure metaphors and translations, and becoming a credentialed expert, comfortable with dauntingly complex equations, is wide but not insurmountable. . Just because I don’t want to be a professional race car driver doesn’t mean I shouldn’t be allowed to drive at all. Surely there is a way to engage with some of the genuine essence of modern physics – even if that means looking at a few equations – without going through years of a standard curriculum.

That’s exactly what I set out to do in The Biggest Ideas in the Universe, a series devoted to the idea that it’s possible to learn modern physics for real, equations and all, even if you are more amateur than professional and intend to remain so. It’s for people who don’t have more math background than high school algebra, but are willing to look at an equation and think about what it means. If you are willing to do this bit of thinking, a whole new world opens up.

Here’s the thing about equations: they’re not that scary. They are just a way to compactly summarize a relationship between different quantities. And while an equation may involve Greek letters, learning to understand an equation doesn’t mean you have to learn to speak and write Greek.

I think we need some common ground, but first let me expand on this resolution/understanding distinction, because it’s key to my dream of talking about physics like a game of baseball. Einstein’s equation does more than relate a specific collection of mass and energy to the curvature of a specific spacetime. It’s a very general relationship, of the form “you give me a distribution of mass and energy, and I’ll tell you how spacetime bends in response to that”. Keeping that promise is what we mean by ‘solving the equation’.

Sometimes solving an equation is easy: if the equation is x=y2 and we are told that y=2, the solution is x=4. Not so hard. But real-world physical equations are more complicated than that, involving ideas of computation (the mathematics of continuous change) and other advanced concepts. Solving such equations can become a full-time occupation for practicing physicists. Therefore, reasonably enough, their education largely consists of learning how to solve equations.

But what if we decided that for a lay physicist it was important not to solve but to understand the equations that explain the world around us, even those that are considered relatively advanced by textbook standards? physical. It turns out to be much more pleasant and exciting. My goal with The Biggest Ideas in the Universe is to make the ideas of modern physics — the real ones, not the watered-down metaphorical versions — accessible to anyone who wants to think a little about equations and their meanings.

Of The Biggest Ideas in the Universe: Space, Time and Motion by Sean Carroll courtesy of Dutton, an imprint of Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2022 by Sean Carroll.