Our Mathematical Universe: My Quest for the Ultimate Nature of Reality

by Max Tegmark

I never got to meet Richard Feynman, but he’s the reason I switched to physics. Although the book wasn’t really about physics, dwelling more on topics such as how to pick locks and how to pick up women, I could read between the lines that this guy just loved physics. Which really intrigued me. If you see a mediocre-looking guy walking arm in arm with a gorgeous woman, you probably wonder if you’re missing something. Presumably, she’s seen some hidden quality in him. Suddenly I felt the same way about physics: what did Feynman see that I’d missed in high school?

We’re all born with curiosity, but at some point, school usually manages to knock that out of us. I feel that my main responsibility as a teacher isn’t to convey facts, but to rekindle that lost enthusiasm for asking questions.

As recently as 1806, when this song was first published, the line “How I wonder what you are” still resonated with many people, and nobody could honestly claim to really know the answers.

If you increase the number of space dimensions beyond three, there can be neither stable solar systems nor stable atoms. For instance, going to a four-dimensional space changes Newton’s inverse-square law for the gravitational force to an inverse-cube law, for which there are no stable orbits whatsoever. I got quite excited when I figured this out, and then realized that I’d just broken my personal scooping record: the Austrian physicist Paul Ehrenfest had discovered this already back in 1917…. Spaces with less than three dimensions don’t allow solar systems because gravity ceases to be attractive, and they’re probably too simple to contain observers also for other reasons—for example, two neurons can’t cross.

Changing the number of time dimensions isn’t as absurd as you might think, and Einstein’s theory of general relativity can handle this just fine. However, I once wrote a paper showing that doing that would eliminate the key mathematical property of physics that allows us to make predictions, thus making it pointless to evolve a brain.

What’s the hallmark of good science? There are several science definitions that I like, and one of them is data compression, explaining a lot with a little. With a good scientific theory, you get more out of it than you put into it.

Back in high school, my friend Magnus Bodin had inspired me with his contrarian philosophy. Since everyone else sent their letters in rectangular envelopes, he made triangular ones. Ever since, when I see the majority do things one way, I instinctively look for alternatives.

Reading Everett’s book taught me a lesson not only in physics but also in sociology: I learned the importance of going back and checking the source material for yourself rather than relying on secondhand information. It’s not only in politics that people get misquoted, misinterpreted and misrepresented, and Everett’s Ph.D. thesis is a great example of something that, to first approximation, everyone in physics has an opinion about and almost nobody has read.

I think that often, in science, the hardest part isn’t finding the right answer, but finding the right question. If you hit on a really interesting and well-formulated physics question, then it can take on a life of its own, automatically telling you what calculation you need to do to answer it, and the rest is almost automatic: even if the math takes hours or days, it feels a lot like mechanically pulling in a fishing line to see what you’ve caught.

For fun, I sometimes compare how the same news story is reported online by MSNBC, FOX News, the BBC, Al Jazeera, Pravda and elsewhere. I find that when it comes to telling the truth, the whole truth, and nothing but the truth, it’s the second part that accounts for most of the differences in how they portray reality: what they omit. I think the same holds for our senses: although they can produce hallucinations and illusions, it’s their omissions that account for most of the discrepancy between the internal and external realities.

evolution endowed us with intuition only for those everyday aspects of physics that had survival value for our distant ancestors, leading to the prediction that whenever we use technology to glimpse reality beyond the human scale, our evolved intuition should break down. We’ve seen this happen again and again with counterintuitive features of relativity theory, quantum mechanics, etc., and should expect the ultimate theory of physics, whatever it turns out to be, to feel weirder still.

From a physics perspective, the easiest way to change a complex system is to find an instability, where the effect of pushing with a small force gets amplified into a major change. For example, we saw that a gentle nudge to an asteroid can prevent it from hitting Earth a decade later. Analogously, the easiest way for a single person to affect society is by exploiting an instability,