COSMIC QUEST: An Interview with Physicist Max Tegmark Part One

Max Tegmark

As a restless teenager, the Swedish-born physicist Max Tegmark wrote code for a shareware game that made him enough pocket change to travel the world. As a brash young theorist he made the cover of Scientific American in 2003 with his wild ideas about the multiverse—including the claim that an identical copy of each of us lives and breathes out there. (Tegmark even says he can calculate the minimum distance to your double.) Now an MIT professor of physics, he recently rallied Stephen Hawking and other luminaries to warn that stumbling into the technical singularity—the point at which machines become more intelligent and nimble than humans—could be catastrophic. All that and more are covered in his first popular book, Our Mathematical Universe: My Quest for the Ultimate Nature of Reality (2014).

On June 8 Max Tegmark will be the keynote speaker at the 73rd Annual Conference of the American Humanist Association in Philadelphia. Below is part one of the interview the Humanist’s science and religion correspondent, Clay Farris Naff, recently conducted with Tegmark. You recently published your first book, and it is an enormous book in many ways. Your cover things as granular as quantum particles, as deep as human consciousness, and as vast as the multiverse. How has it been received?

Max Tegmark: The book is essentially my synthesis of what I’ve learned so far in my career, and it’s been so exciting to see how many people from different walks of life are interested in these things. Mainly the reaction has come in very enthusiastic emails from people who say that it made them think in new ways and ask new questions.

I wrote the book largely for the person who sits next to me on the airplane who is intelligent and interested but hasn’t spent much time studying physics. It’s very interesting to share not only the lessons we’ve learned by studying our world, but also how much fun it is to be on this quest. I hope to inspire kids to study science. One of the things that made me study science was realizing that other people found great joy in it. You write that in high school you found physics terribly boring. What were the key events that pushed you into physics after all?

Tegmark: I actually did my undergrad in economics. I was quite concerned with how stupidly we were managing our planet, and I thought the best way to influence people’s behavior was probably through their pocketbooks. But I became disillusioned with economics. At the same time I had a girlfriend who was studying physics, and her books seemed so much more interesting than mine. Our love didn’t last, but my love for physics did.

A classmate had also given me a book by Richard Feynman, which wasn’t even a book on physics but a personal story. I was really intrigued that he loved physics, a subject I had found so boring. It piqued my curiosity to find out what I had missed in high school. So I read a book of physics lectures he had written, and before I was through the first chapter I was sold. Physics isn’t some boring bag of tricks to calculate, say, density; it’s the ultimate detective story to find out the ultimate nature of this wonderful world. That’s why the subtitle of my book is My Quest for the Ultimate Nature of Reality. And if readers get into the book, it won’t just be my quest. Growing up in Sweden, did you have a sense of yourself adhering to a religion or a set of humanistic values?

Tegmark: I always had a strong sense of humanistic values. My mom’s father was a Lutheran minister, and my father’s grandfather was a rabbi, but [neither] of my parents practiced religion at all. My grandma took me to church a few times, and Santa Claus would show up every Christmas, but that was the extent of it. Sweden is, of course, a very secular country.

I was quite shocked when I came to the United States to see such a conflict between religion and non-religion. That just didn’t exist in my world. Some people were religious and some were not, but it never created any practical problems or disputes at all. It was only when I came to the United States that I discovered all the acrimony. Yes, something that continues today, unfortunately. Let’s turn to the themes of your book, because it is an attempt to understand our world at the largest conceivable scales through naturalistic inquiry, isn’t it?

Tegmark: That’s right. I’m a very curious person, and I have a passion for always seeing if I can take yet another step back and look at the even bigger picture. That’s why when I started grad school and discovered there was a subject called cosmology, I thought, “Wow, what an awesome thing to study!” It’s the biggest thing that we can study with the methods of science. You’ve taken the idea of the multiverse, which has certainly gained traction in the last decade or so, and you’ve extended it even further to four different levels. It’s unfair to ask you to unpack all of that complexity in a short interview, but could you give us an overview of the journey that we take in your book?

Tegmark: Absolutely. We humans have again and again underestimated not only the size of the cosmos—a planet, a solar system, a galaxy, a universe, maybe a hierarchy of parallel universes—but we’ve also repeatedly underestimated the power of the human mind to understand our cosmos. It also struck me that there was a lot of confusion with the term “parallel universes,” which was being used to describe any number of different things. There’s no better way to have an argument generate more heat than light than when people, without realizing it, are talking about different things. That’s why I created this classification of four levels of the multiverse.

The Level I multiverse is simply the idea that the universe may go on forever, in which case the part that we call our universe, which is the spherical volume from which light has had a chance to reach us so far in the 13.8 billion years since the Big Bang, is obviously not all of it. This didn’t go down so great when Giordano Bruno voiced the idea—he was burned at the stake in 1600—but now it’s fairly noncontroversial that there is at least more space than we have access to with our telescopes.

So, Level I is simply space going on much farther than we have access to. If you go to a Level I parallel universe you’d learn the same things in physics class, but you’d learn different things in history class.

The Level II multiverse, if it exists, is still in the same three-dimensional space but even farther way, and there you might learn different things in physics class as well.

And the Level III multiverse—that’s an idea that comes to us when we study not the largest but the smallest scales of the universe, so it’s governed by quantum mechanics. It’s an idea first put forward by Hugh Everett as a Princeton grad student in 1957. He wasn’t burned at the stake, but he got burned in the job market.

More recently, though, this has emerged in polls as one of the most popular interpretations of quantum mechanics, and if it’s true then there is a still larger reality, and moreover it has cool technological implications. If it’s true, then you can build quantum computers in the future and solve all kinds of problems dramatically faster than ordinary computers can.

Finally, the biggest and most controversial multiverse of them all is the Level IV multiverse, where it’s not just the apparent laws of physics, as manifested by constants and so on, that vary but also the most fundamental laws of physics. Is it fair to say that you think there is at least a possibility, if not a probability, that all four coexist?

Tegmark: Absolutely. They can logically coexist much like Russian dolls can be inside one another. Of course, my job as a scientist is not to believe in parallel universes or disbelieve in them. My job is simply to follow the evidence wherever it takes me. But I love to bet, and I’d place a pretty good chunk of money on all of them existing.

It’s important to remember that although this can sound speculative and flaky, parallel universes are not a theory. They are a prediction of certain scientific theories. It’s logically anathema to accept a theory and then reject its predictions. For example, if you accept the theory of general relativity, you can’t just turn around and reject its prediction of black holes because for some reason you don’t like black holes.

In other words, if you don’t like black holes, come up with a better theory than general relativity. It’s exactly analogous with these parallel universes. For example, the theory of inflation, which was spectacularly confirmed last month by the Bicep-2 experiment, predicted generically that there is a Level I multiverse. If you want to get rid of the Level I multiverse, you have to come up with a better theory than inflation. I’m glad you raised the example of black holes. Sometimes a theory a can be sound but incomplete, and in the case of Einstein’s theory predicting black holes, there’s at least an intriguing possibility raised by Steven Hawking recently that perhaps black holes can’t persist, not because the theory is wrong but because there are additional constraints on their existence that might make them impossible. Isn’t that true for the extension of any untested predictions of theories—that they may run into things we don’t yet know about?

Tegmark: That’s a beautiful example. If it turns out that the interior of black holes is actually different from what we thought, it’s simply because the mathematical theory of general relativity isn’t quite correct, and when we put in quantum effects you get different predictions—just like general relativity previously overthrew Newton’s theory of gravity, right? That is exactly science at its best. But until we have a new theory that actually makes some predictions, we need to take these predictions as seriously as the theories that predict them.

But let’s take a step back from the mathematical theory. Suppose you have a paperclip factory producing paperclips with some sort of machine. It’s pretty typical that that machine produces not one paperclip but many paperclips, right? In the same spirit, there’s clearly some sort of universe-producing mechanism that produced our universe. It’s not such a crazy thought that it might have created other universes, too. Right. If what you’re saying is correct, we have to add an “s” to universe.

Tegmark: I’m not saying there are other universes. I’m saying we have to guard against this emotional bias against removing ourselves from center stage. We’ve made that mistake so many times before. Most of the multiverse critiques are of that form.

Next up in Part II: Is there an identical copy of each of us, out there, somewhere?