Paul Davies, theoretical physicist

The noted author talks about the search for “alien” life on Earth, the origin of the universe, and taking science to the people. Interview by Michael Wall

May 25, 2009

Photo courtesy of Tom Story/Arizona State University

Paul Davies is an ambitious guy. The research institute he established at Arizona State University—the Beyond Center for Fundamental Concepts in Science—lists the following areas of inquiry on its website: 1) the origin of the universe; 2) the origin of physical laws; 3) the nature of time; 4) the foundation of quantum mechanics and quantum biology; 5) the origin of life; and 6) the search for extraterrestrial intelligence.

And as Davies figures out how the universe works, he wants everyone else to understand it, too. He’s written 27 popular-science books with titles likeHow to Build a Time Machine and The Mind of God. He’s penned more than 400 newspaper and magazine articles, and he has helped produce countless radio and television programs about the big questions in science.

Davies grew up and trained in England, earning his Ph.D. from University College London in 1970. He moved from the U.K. to Australia in 1990, then came to the U.S. in 2006. His research has shed light on the nature of black holes and the cosmic background radiation left over from the Big Bang. In the 1980s, he became interested in astrobiology—the study of life’s origins and the search for it beyond Earth. He pioneered the theory that life may have originated on Mars, then traveled to Earth in rocks ejected by comet or meteorite strikes.

At the 2009 meeting of the American Association for the Advancement of Science in Chicago, Davies spoke about the possibility that life evolved more than once on Earth. Afterward, he sat down to discuss the search for this so-called “shadow biosphere,” the laws of physics, and why we know so much about the universe. He needed little prompting; his eyes shone as the words came tumbling out.

How did you get into astrobiology?

To a physicist, life looks like a miracle. It’s like a state of matter that has no parallel in the physical world. So it’s deeply fascinating to think, “How did it get started in the first place?” When it became clear that rocks can travel between Earth and Mars, it occurred to me that life could as well.

You’ve said that in the ‘60s, people asked, “Why even think about life on other planets?” But now it's accepted as a real possibility. What changed people’s perceptions?

I honestly don’t know. It's really weird, because nothing has changed on the ground. Now the default position is, “There’s nothing special about life. It’s got to be all around the universe.” It’s fashion, politics, philosophy. It’s not science, because we’re just as much in the dark about how life began. When I lecture on this, I always quote [French biologist] Jacques Monod, who said in the early ‘70s, “Man at last knows that he is alone in the immensity of the universe, out of which he emerged only by chance.” Then [Belgian biochemist] Christian de Duve, who said, “Life is a cosmic imperative.”

And there’s only a span of two decades between those statements.

Yeah. And the science of biogenesis hasn’t really progressed at all during that time.

"I get upset when I come across people who think science doesn't matter. Why would you not want to know whether it's possible to travel in time? Why would you not want to know how the universe began? Have you no soul?"

How did you get interested in the shadow biosphere?

I was at a NASA astrobiology conference in 2003. I can remember thinking, “If life is widespread and forms easily, how do we know it didn’t form many times on Earth?”

This is the only planet we know of where life has evolved. So why not look here to see if it’s happened more than once?

Right. Because it’s cheaper than going to Mars, for example. And the consequences are momentous. This is basically testing whether life is found throughout the universe—an integral part of the laws of nature—or whether it’s some freak event.

Where would we look most fruitfully to find something that might not be “normal” life here on Earth?

There’s a difference between where it is most likely to be and where is the easiest place to look. It’s easiest to look in places that are beyond the reach of known life. My favorite is very high-UV [ultraviolet radiation] environments, like the upper atmosphere. The most likely environment is actually intermingled with known life, because that’s the benign environment. But then it’s going to be hard to untangle. You look at a billion microorganisms of a million different species, and three of them are shadow life. That’s going to be tough.

How would you know that what you’re looking at is a separate origin of life?

It’s going to be a matter of judgment about how different it is. If we found protein-based life with the same amino acids but a different genetic code, for my money that would simply be an evolved branch. But if it had a completely different set of informational molecules, then surely it’s going to be different.

Do we have any leads?

Well, nanobes [common rodlike structures about one-tenth the size of the smallest known bacteria] may be worth a second look. But I’ve always been skeptical about nanobes.


If there are nanobes all around us, and they’re living, surely we can determine that one way or the other. Can’t we just get ahold of these things? I like arsenic life [the idea that alternative organisms may use arsenic in their metabolism rather than phosphorus, as “normal” life does]. It’s a little wild, that one.

It seems wild because arsenic is poison to us. But arsenic is very similar to phosphorus, and more abundant on Earth, right?

There are some places where arsenic is more abundant. It’s not inconceivable to think of places and epochs in the past where arsenic would’ve had advantages. And it wouldn’t cost much to take a look. There are organisms [in arsenic-contaminated lakes] that use arsenic as an energy source. They strip out the energy and spit out the arsenic. If you’re going to look for arsenic life, that’s a good place to start.

Astrobiology is just a sidelight for you.

I’m a cosmologist and theoretical physicist; that’s what I mostly do. The last book I wrote is about the nature of the laws of physics, why they have the form that they do, and the possibility that the laws may not be immutable.

It’s aroused a little bit of controversy.

That’s intentional.

Your basic thought is that these laws were not imposed from above.

Right. They’re not transcendent, the maker’s mark imprinted on the universe at the moment of its birth from some external agency. But that they coevolved with the universe, emerged with it, and are part of it. It’s a sort of U-turn against Platonism. Most of my colleagues are Platonists, so they don’t like that.

They would say, “There is no reason. The laws just are.”

Right. “It’s a mystery, and I’m happy with that.” I’m saying, let’s try to bring the laws of physics within the scope of scientific inquiry and not just shrug and say, “It’s a mystery.”

How do you show that these laws evolved with the universe?

I stuck my neck out and said I think there is an inherent flexibility or fuzziness in the laws. This fuzziness has a measure that we can specify by asking, “What is the total information content of the universe?” It’s easy to work out: 10122 bits. You might say, “That’s such a huge number. You would never notice errors.” But there is a situation in which you might well notice, and that is quantum entanglement. If you have 400 entangled atoms, that would already have more components of the wave function [ways to describe the atoms’ possible positions and configurations] than there are bits of information in the entire universe. So I would expect something to go a bit wrong with quantum mechanics at that stage.

What sorts of things would happen?

I can’t tell you precisely. Schrodinger’s equation, which predicts how systems evolve, would turn out to be wrong. Four hundred entangled particles—is that feasible? Well, the quantum computing people claim they’re going to get 10,000. There are billions of dollars going into this. If you believe the hype, they’re going to do it.

Would that be a test to see if the laws are fuzzy?

I think it would be.

Do you subscribe to the multiverse theory—that there are an infinite number of universes out there—as an explanation for the universe’s origin?

I usually say, “Two cheers for the multiverse,” because it’s better than just saying, “God did it, and leave it at that.” But the multiverse has all sorts of problems. You still need a universe-generating mechanism. You need to have laws to distribute among the different universes. Then you can still ask, “Why that multiverse? Why those metalaws? Where have they come from?” You don’t really solve the problem.

Is it the best explanation we’ve got now?

It’s probably the best in terms of learned papers in the journals. But I would prefer something that directly links life and consciousness to the underlying law, rather than just throwing all these universes at it and saying, “It’ll work out somewhere.” That’s a much harder thing to do.

Do you think there’s going to be a time when our quest for knowledge breaks down, a point beyond which we cannot go?

I hope not. But there’s no fundamental reason why we should be privy to the secrets by which the universe runs. After all, our minds have been built by evolution just to survive in the proverbial jungle. I think we’ve already done so well that it’s suspicious.

Suspicious? Do you think there’s some overarching order to the universe?

It’s only a feeling, but yes. I think there’s a deep link between life, consciousness, and the universe. It all sounds a bit mystical, but we have no a priori right to expect to understand anything. I’m not saying that humans are at the center of creation or anything of that sort. I’m simply saying that the emergence of life and consciousness is built into the universe in a fundamental way. The cosmic order and our understanding of the universe are linked. Was that link put there by a god who pre-existed the universe, designed human beings with rationality? I think it’s more subtle than that.

You’re a prolific science popularizer. How do you feel about your responsibility to get information to the public?

I find science so fascinating and so important that I want to share it. I get really upset when I come across people who think science doesn’t matter. Not only does it matter, it’s fantastically, wonderfully exciting. Why would you not want to know whether it’s possible to travel in time? Why would you not want to know how the universe began? Have you no soul? We scarcely stop to think just how stupendous it is that the human mind is actually able to read the hidden subtext of nature. I think that’s a wonderfully uplifting thing. I like to tell people about it, and I really can’t stop.

Michael Wall, a graduate student in the Science Communication Program at UC Santa Cruz, earned bachelor's degrees in ecology and evolutionary biology and history at the University of Arizona, and a Ph.D. in evolutionary biology from the University of Sydney, Australia. He has worked as a reporting intern at the Salinas Californian, the science unit of, and the news office of the SLAC National Accelerator Laboratory. He will work for six months as a science writing fellow at the Department of Energy's Idaho National Laboratory in Idaho Falls.

© 2009 Michael Wall