The Big Idea: Chad Orzel

A couple of years ago physics professor Chad Orzel (and his dog Emmy) endeavored to explain physics to humans with How to Teach Physics to Your Dog. That book went on to become a worldwide success, with translations into ten languages to date. How do you follow up? By diving deeper into an especially strange and wonderful aspect to physics — the part we get from Einstein. And thus How to Teach Relativity to Your Dog, the latest scientific adventure from Chad and Emmy, and also, the universe. Here’s Chad to talk to you about his position on it all.


In a way, a book about Einstein’s theory of relativity is uniquely suited to a series about Big Ideas. Relativity, at its heart, is a theory built on a single Big Idea:

The laws of physics do not depend on how you’re moving.

For all its fearsome reputation, everything stems from that single, simple idea. Whether you’re moving or standing still, floating in space or on the surface of a planet, you will see the laws of physics work in exactly the same way.

All that stuff about the speed of light being the same for everyone? The speed of light is a consequence of the physics of electromagnetism, expressed in Maxwell’s equations. Since the laws of physics do not depend on how you’re moving, you will always see light move at exactly the same speed.

All that stuff about moving clocks running slow, moving objects shrinking, and twins who are different ages? Because physics is the same for all observers, and the speed of light is a constant, moving observers must disagree about how much time passes between two events, and even about the order in which they occurred.

All that stuff about gravity warping space and bending light? It’s a consequence of what Einstein called “the happiest thought of my life,”the realization that there’s no difference between falling due to gravity and floating in space. Once you recognize that, the bending of light and the warping of space follow.

Einstein’s great achievement wasn’t that he invented all these weird phenomena– other scientists like Hendrik Antoon Lorentz, George FitzGerald, and Henri Poincaré; came up with most of those well before Einstein. Einstein’s great contribution was showing that all the weird stuff is inevitable once you accept the central principle that the laws of physics do not depend on how you’re moving.Einstein succeeded where others had failed because he provided clear,compelling, and logical explanations for the strange results that others had balked at.

If relativity is so inevitable, though, why does it seem so weird? And what does a dog have to do with any of this?

Relativity seems weird because its biggest effects occur in situations that are very far removed from our everyday experience: objects moving very close to the speed of light, or exotic objects like black holes whose mass is great enough to significantly warp space and time.Relativity’s predictions have been confirmed to an amazing degree of precision in experiments ranging from subatomic particles to the entire universe. But those experiments require sensitive scientific equipment– particle accelerators, telescopes, and ultra-precise atomic clocks– that isn’t the sort of thing you have lying around in the garage.

That’s because relativity produces big effects only in circumstances that are very far removed from our everyday experience. When we approach the theory, we bring with us a lot of experience witheveryday situations, where relativity makes almost no difference, and relativity confounds the expectations we have based on that experience.

Which is where the dog comes in. Dogs, unlike humans, come to physics with very few preconceptions about how the world ought to work. To adog, the world is an endless source of surprise and wonder. The slowing of a moving clock is no more perplexing to a dog than the operation of a doorknob, which puts them in a good place to begin to understand the theory.

And we’ve got a terrific dog to help with this process: our German shepherd mix, Emmy, back for more after How to Teach Physics to Your Dog (previous Big Idea). Each chapter of the book opens with a dialogue between me and Emmy, in which she latches on to some aspect of relativity as relevant to her interests, and I gently explain how it really works. That’s followed by a more detailed explanation for interested humans, interrupted occasionally by questions from Emmy, who helps clear up points that people reading the book might find confusing. And, of course, since relativity involves multiple moving observers, there are cameos from a bunch of other dogs owned by friends and family, and even from my sister’s dastardly cat, Nero.

So, while the central idea of Einstein’s theory is that physics doesn’t depend on how you’re moving, the central idea behind How to Teach Relativity to Your Dog is that the best way to understand Einstein’s theory is to think like a dog. If you can put aside human preconceptions about what ought to happen, and work through the consequences of the principle of relativity, you can better appreciate the power and beauty of the theory.


How to Teach Relativity to Your Dog: Amazon|Barnes & Noble|Indiebound|Powell’s

Read an excerpt. Read the author’s blog. Follow him on Twitter.

11 Comments on “The Big Idea: Chad Orzel”

  1. My Physics Department Chair wife, myself, and our dog, have long considered Chad Orzel the best in the cosmos at what he does: a nonlinear combination of Physics teaching, blogging, parenting, and book authorship.

    To be fair, though, my dog believes that the 3-dimensions of space plus one dimension of time that we perceive the universe to be are a manifestation of a quantum cellular automaton operating according to discrete rules at a 2-dimensional boundary of the holographic cosmos.

  2. I’m afraid to ask where Emmy wears her past light cone.

    This is my new favorite comment about the cover. It’ll be hard to top.

    OK, now for the real challenge. Go write How to Teach String Theory to Your Dog.

    They say you never really understand a subject until you try to teach it to your dog, but I don’t think anybody understands string theory that well…

  3. One of my favorite passages from my intro physics text (Halliday and Resnick, PBUT,) was the intro to the relativity section, which basically says, “Look, this doesn’t make any sense the first time you look at it. We admit that. It’s totally bizarre. But follow along with us, do the math for yourself, and you’ll see that it’s *logically* bizarre.”

  4. I attended Chad’s Sunday afternoon lecture at Boskone. Really, really good time. Chad was able to break down and explain some pretty complex ideas in a way that made sense. I’m not completely science or physics-ignorant but I definitely came away with a better understanding of the subject.

    Shame the lecture was stuck in the smallest Boskone room, though. Five minutes into the lecture it was already packed beyond capacity, and people kept trying to come in and wandered back out, discouraged by the lack of seating. Maybe the organizers didn’t think it’d be that popular…the fools.

  5. “OK, now for the real challenge. Go write How to Teach String Theory to Your Dog.”

    Why? I might as well teach it to jump into a meat grinder.

  6. One quibble with the post: Under relativity. there actually is a difference between acceleration and gravity — it’s just not visible at a single point! The gravitational field is curved and tapered, producing various sorts of tides. Notably, the two balls will fall parallel in an accelerating framework, but in a gravity field they will fall slightly toward each other.

    That said, I haven’t read the book yet, but I’ve read a fair bit of Orzel’s blog, and from that I’m sure the book is great.

  7. @ Dave Harmon

    There’s also the possibility that an accelerating observer, unlike an inertial observer, would observe Unruh radiation, though that has not been conclusively proven.

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