Lawrence Krauss is a rare animal.
He is a physicist with landmark results under his belt, including the prediction that most of the universe’s energy is stored in free space. He is the author of nine popular books (soon to be 10), including the best-selling The Physics of Star Trek (where I learned that the Enterprise would need to burn 81 times its entire mass in fuel to accelerate to half light-speed).
Krauss is also not one to mince words. Whether it’s on the topic of philosophy (“physics needs philosophy but not philosophers”) or religion (he ran an article in The New Yorker last month with the title “All scientists should be militant atheists”), he is outspoken and occasionally controversial.
That he enjoys a direct or irreverent comment clearly comes through in conversation. But more important to him is his love of science, and his view of the scientific method not just as a practical tool, but as a cultural value that needs to be disseminated and defended, controversy or not.
He spoke to Nautilus from his home in Oregon.
Why is gravity so hard to unify with the other forces of nature?
The beautiful features of the other theories is that quantum fluctuations—and there are an infinite number of them—could in principle produce infinite contributions, which would mean you couldn’t calculate with those theories. But it turns out that there’s a symmetry associated with those theories that causes those contributions to be manageable. You could ignore the infinities and produce predictions that actually work.
It turns out [that] in general relativity, because of its mathematical formulation, you can’t ignore those infinities. At some level the quantum mechanical contributions can’t be tamed, and they produce nonsense. It really is just because of the nature, the mathematical nature, of general relativity and that’s one of the features. The other is the conceptual problem: If space and time are the variables of general relativity, as they are, then to have a quantum theory of space and time is conceptually very complicated.
But right now that’s not the problem. The problem is mathematical—you have to make sure that infinite fluctuations of the gravitational field at very small scales don’t screw up the theory, and right now they screw it up. That’s why we’re reasonably certain that general relativity is not the full story when it comes to gravity, that the theory will have to be modified just like all other theories have been modified as you go to ever smaller scales.
There are two possibilities—that the theory will be modified by a quantum theory that is itself scale dependent; or that the theory will be modified by something like string theory, which produces an ultimate theory [that] describes the universe all the way down to the scale size zero. We’re not talking about very much landscape here. The scale where quantum mechanics of gravity becomes important is something like 10-30 centimeters or so, and we’re talking about [if] you can have a theory that describes the universe from 10-30 centimeters down to zero. As my friend, I think Frank Wilczek, has said about string theory, it’s not a theory of everything, it’s a theory of almost nothing.
How can we tell if gravity is quantum?
Freeman Dyson, who is a brilliant physicist and a contrarian, he had pointed out based on some research—he’s 90 years old, but he had done some research over the years—I was in a meeting in Singapore with him when he pointed out that we really don’t know if gravity is a quantum theory. Electromagnetism is a quantum theory because we know there are quanta of electromagnetism called photons. Right now they’re coming, shining in my face and they’re going into the camera that’s being used to record this and we can measure photons. There are quanta associated with all of the forces of nature. If gravity is a quantum theory, then there must be quanta that are exchanged, that convey the gravitational force; we call those gravitons. They’re the quantum version of gravitational waves, the same way photons are the quantum version of electromagnetic waves. But what Freeman pointed out is that there’s no terrestrial experiment that could ever measure a single graviton. He could show that in order to build an experiment that would do that, you’d have to make the experiment so massive that it would actually collapse to form a black hole before you could make the measurement. So he said there’s no way we’re ever going to measure gravitons; there’s no way that we’ll know whether gravity is a quantum theory.
What I realized, and Frank and I codified in our paper, is that actually the universe acts like a graviton detector, in [the] sense that processes in the early universe produced phenomena that could be observed today as gravitational waves. But those events, those processes, will only work if gravity is a quantum theory. If gravity isn’t a quantum theory, we won’t see these gravitational waves from the very early universe, which BICEP thought they saw. Now BICEP may not have seen gravitational waves from the early universe, but the fact that we recognize that if this phenomena called inflation happens in the very early universe, and if it produces gravitational waves, that will tell us that gravity is a quantum theory; therefore, all of the problems of quantum gravity will need to be addressed by theorists, giving job security for generations.
What would the detection of gravity waves lead to?
It will be the new astrophysics of the 21st century. And we’re building gravitational wave detectors to do just that because they’ll allow us to see the moments of formation of black holes and collisions of black holes and maybe, because gravitational waves are so weak, they’ll propagate from the very early universe to now without being impeded, so they might give us a window on the universe when it was only a millionth of a billionth, of a billionth, of a billionth of a second old, which is pretty close to the Big Bang.
We’d be able to see the formation of black holes. We’d be able to see colliding neutron stars. We don’t even know all of the things [we’d] be able to see. Massive cataclysmic events where huge amounts of matter move around in a explosion or a collapse produce gravitational waves, and if general relativity is correct, in the final stages of formation of a black hole, huge amounts of energy should be released in gravitational waves and we may be able to see them. In the moments where two black holes collide forming a big black hole or two neutron stars collide forming a large single black hole, there should be huge numbers of gravitational waves produced—we’d be able to see that, and we’d learn about properties of general relativity and the regime of strong gravity and we’d learn a lot about the nature of black holes and other astrophysical objects in the universe that otherwise we literally cannot see.
Do you still carry a card in your wallet that proves the Big Bang happened?
Hold on a second. The answer is yes, of course. I do it partly because people like you ask me the question and there it is. The Big Bang really happened. I’d like to explain that to Ben Carson someday, but I don’t think he’d understand.
The card compares the predictions of the abundance of light elements—hydrogen, helium, and lithium—from the Big Bang. We predict that they vary by ten orders of magnitude, that 25 percent of the universe is helium and one part in 10 billion of the universe is lithium. Then when you compare with observations, which is a thin line here, they agree precisely, over ten orders of magnitude. Our predictions of the abundance of light elements from the Big Bang agree with observations. There may be better ways, but I don’t know of them, to say the theory really works.
What is missing in the public perception of science?
We live in a society where people don’t have any cultural appreciation of science at a basic level. Our discoveries about the universe are some of the most amazing ideas that humans have ever developed and the fact that some people are so afraid of reality, that reality might confront their a priori beliefs, that they refuse to even listen is of great concern. If it was just the Big Bang, I wouldn’t care; but if that’s one step on a slippery slope that takes people to not believing in evolution, to not accepting the world the way it is, and instead [to] making inane laws based on the perceived wisdom of Iron Age peasants [from] 2,000 years ago …
I think it’s more of a symptom of many of the aspects of our culture that you can lie with impunity and people would rather believe in what they want to believe—whether it’s ideological or religious—rather than accept the evidence of reality if it’s inconvenient. I mean as Al Gore put it, an inconvenient truth is inconvenient—and for many people, they’d rather bury their heads in the sand—or under water as it may soon be the case. Look, there have been science communicators for a long time, but I think the urgency of scientists communicating results of science has developed over time because we live in a time now where we are globally affecting the planet and we can no longer afford the luxury of just ignoring the results of science or discounting them in a variety of areas because then we do so at our peril.
You met the great physicist, Richard Feynman, as a young student. How did he influence you?
When I was a kid in college, I was involved in an organization in Canada of undergraduate physics students and Feynman came to speak to that conference. My girlfriend came with me—and she was one of the few women there—and Feynman therefore spent a lot of time with me, and her. I spent the weekend talking to him. He also taught me how to dance. So it was an amazing experience for a young person and as I say, that—and watching him, and reading him—has been a huge influence on me. I’m not the only one of course, but certainly I like to think that the joy that he conveyed when he talked about science is something I like to channel when I talk about science. That and the fact that he was bold and yeah, his boldness was important as well. He told me to also seek out adventures and I’ve tried to do that.
One of the reasons I was honored to write the book is that many years later when I was at Harvard and I gave a lecture at Caltech, Feynman asked a question at the colloquium and then came up afterward to talk to me and I was desperately wanting to tell him that, remind him that I was the young person that he’d met earlier and etcetera etcetera and this very obnoxious young assistant professor wouldn’t leave me alone and finally Feynman walked away and I thought well I’ll catch him later; but then he died before I ever got a chance to tell him that and so I felt like wow, I missed my chance. So the book was in some sense thanking him for, since I never had the chance to to do that directly.
Tell me about your interaction with the philosopher, David Albert.
I never interacted with him at all. I wrote a book about cosmology and he wrote a book review about a book he wished I’d written about cosmology and the two had nothing to do with one another as far as I know. He wrote an acerbic review of a book that he’d wished I written without really understanding what I’d written, without mentioning the word cosmology so yeah. So apparently it caused a stir and I thought it was very, I thought it was mediocre. I mean as I said I would’ve given, if it had been an English student, I would’ve given him a C minus. Normally when you write a book review, it should be about the book; and the only part of the book that as I remember he actually reviewed was the afterword, by Richard Dawkins, which I found again as something—if I was an English professor—I would’ve failed the student for it.
Does physics need philosophy?
We all do philosophy and of course, scientists do philosophy. Philosophy is critical reasoning, logical reasoning, and analysis—so in that sense, of course physics needs philosophy. But does it need philosophers? That’s the question. And the answer is not so much anymore. I mean it did early on. The earlier physicists were philosophers. When the questions weren’t well defined, that’s when philosophy becomes critically important and so physics grew out of natural philosophy, but it’s grown out of it, and now there’s very little relationship between what physicists do and what even philosophers of science do. So of course physics needs philosophy; it just doesn’t need philosophers.
Except that physicists themselves are doing philosophy, but they’re not credentialed to do that, if you wish. They’re just asking questions, trying to do critical analysis, distinguishing between hypotheses, using logic—all the kinds of things that philosophy is very important for; so I don’t mean to discount the activity of philosophy, because it’s what we all do in a real way. And philosophy is in many aspects of life quite useful. I recently had a long dialogue on stage with Noam Chomsky about philosophy. I’ll be having a dialogue later this month with a friend of mine, Peter Singer, who’s a well-known philosopher, and these questions that they raise are vitally interesting in many areas of of human activity. It’s just in physics, they’re not.
In your book, A Universe from Nothing, you ask how something came from nothing, and answer that nothing is not what we thought it was. Is that avoiding the question?
No. We’re changing the question, but that’s okay; that’s what we do in science! You know, I mean, that’s what we call learning. Some people get upset that we change the meaning of “nothing,” but we changed the meaning of light when we realized it was made of photons. I mean it really is what learning is all about.
So we now realize that “nothing” is a very subtle concept. I mean, it was never well defined anyway. Most of the religious people who object to my definition of nothing never defined it themselves. Here’s what their definition of nothing is: Nothing is that from which only God can create something. Well you know, they create this useless definition, but really the nothing of the Bible was what we would call empty space now, eternal empty void—what many people thought our universe was over most of it, and 100 years ago, that was the conventional wisdom. There was one galaxy surrounded by an infinite dark void and that kind of nothing is really simple. That kind of nothing creates something all the time because elementary particles pop in and out of that kind of nothing all the time—they’re called virtual particles. So even those who criticize our definition of nothing never really had a good definition of it.
You might say it’s non-existence, but what do you mean non-existence of? Again, I would argue, when I talk about the universe from nothing, I’m talking about a universe in which not only no particles, no radiation existed, but no space and no time existed in what is now our universe; all of that came into existence. Now you can say well, did anything else exist? And I say well, that’s largely a semantic and maybe [a] useless question because it could be that there’s, it’s like, turtles all the way down, that there was other, that our universe arose out of a multiverse; or it could be that there was absolutely nothing—there was no space, no time, and space and time popped into existence. But it seems to bother people that you can talk about a universe not existing and then existing; but it doesn’t bother people that a photon emitted by lights that are on in the room I’m outside of right now didn’t exist before the atoms that emitted it. Our universe could just be a quantum version of that photon and yes, it bothers people because it doesn’t relate, it doesn’t agree with their classical notion of what nothing might be. Or nonexistence is problematic for them because they worry about cause and effect and things like that. But for example, if space and time didn’t exist before our Big Bang, then the whole notion of cause and effect has to go out the window. If there was no “before,” then you can ask about causes in that sense—that bothers people! And that’s okay; science is meant to bother people because it means we’re not thinking about things correctly. If it bothers you, then do something about it.
Do scientists consider the scientific method to be sacred?
No it’s not sacred. We hold the scientific method in high regard because it works. If it stopped working, we’d throw it out! I think we don’t hold anything sacred, but we’re utilitarians, to be a philosopher for a moment. If it doesn’t work, we don’t care about it. If it works, we use it. You can call that sacred, but we only use what works and the scientific method works; revelation doesn’t work. Get over it!
How do you view religious scientists?
Humans are capable of carrying two completely discordant views at the same time. There are geologists who study ancient rocks and talk about and write professional papers about phenomena that happened hundreds of millions of years ago, but themselves claim to believe the earth is only 6,000 years [old]. How can you do that? I don’t know how you could do it, but some people manage to be able to do it. So the fact that you can be religious and do science, it’s clear you can because there are scientists who are. And as I pointed out, for those scientists, their religion doesn’t enter into the science because they care about how the universe really works and then in the background they say, well maybe it was God that made it all be that way. But when they’re worrying about how the universe works, they don’t think—as the famous biologist, J.B.S. Haldane once said, he didn’t think there was some angel or God twiddling the dials in his experiment in the laboratory and so, as he put it, since he was an atheist in the laboratory, why not be an atheist outside the laboratory.
Did sci-fi get you into science?
It’s hard; it’s a chicken and egg problem. Did I like science fiction when I was a kid because I liked science? Or did I like science because I liked science fiction? I think the two fed off each other. Science fiction is nice because it overcomes many people’s inhibitions about talking about science. As I think I might have written in the introduction of The Physics of Star Trek, you go to a party, you tell people you’re a physicist, they go wow, how about those Yankees or something—whatever the subject to change it in—but then you start talking about time travel or warp drives or whatever, then people get excited! So science fiction provides an opportunity to provide a way for people to begin to enter into the scientific questions that really excite us all without feeling they have to get all the intellectual baggage. Now for some people, that’s as far as they’ll take it. They’ll say wow, those are interesting questions and that’s an interesting story; but for other people, it’ll prompt them to begin to wonder, [I wonder] how the real universe works and that’s why I wrote The Physics of Star Trek, because the real universe is far more interesting than any science-fiction book that’s ever been written.
What would you be if you weren’t a scientist?
My mother wanted to be a doctor, so I might have fallen for that. I’d like to say I might have been a movie star, but it turns out I am now, so I guess I’m having my cake and [eating] it too.