Because if you look at what quantitatively has come out of the new results, they’re exactly consistent with the old results. Which also validate inflation. They reduce the error bars a little bit, by a factor of 2. I don’t know if that’s astounding. But what’s intriguing to me is that while everything is consistent with the simplest [inflation] models, there’s one area where there’s a puzzle. On the largest scales, when we look out at the universe, there doesn’t seem to be enough structure—not as much as inflation would predict. Now the question is, Is that a statistical fluke?
That is, we live in one universe, so we’re a sample of one. With a sample of one, you have what’s called a large sample variance. And maybe this just means we’re lucky, that we just happen to live in a universe where the number is smaller than you’d predict. But when you look at the CMB map, you also see that the structure that’s observed is in fact, in a weird way, correlated with the plane of the Earth around the sun. Is this Copernicus coming back to haunt us? That’s crazy. We’re looking out at the whole universe. There’s no way there should be a correlation of structure with Earth’s motion around the sun—the plane of the Earth around the sun, the ecliptic. That would say that we’re truly the center of the universe.
The new results are either telling us that all of science is wrong and we’re the center of the universe or maybe that the data are simply incorrect. Or maybe it’s telling us there’s something weird about the microwave-background results and maybe, maybe, there’s something wrong with our theories on the larger scales. And, of course, as a theorist I’m certainly hoping it’s the latter, because I want theory to be wrong, not right. Because if it’s wrong, there’s still work left for the rest of us.
14
Einstein: An Edge Symposium
Brian Greene, Walter Isaacson, Paul Steinhardt
Brian Greene: String theorist, Columbia University; author, The Fabric of the Cosmos
Walter Isaacson: President and CEO, The Aspen Institute; author, Einstein: His Life and Universe
Paul Steinhardt: Theoretical physicist and Albert Einstein Professor of Science, Princeton University; coauthor (with Neil Turok), Endless Universe: Beyond the Big Bang
INTRODUCTION by John Brockman
The coincidence in spring 2007 of Walter Isaacson’s Einstein biography (Einstein: His Life and Universe) hitting the #1 spot on the New York Times bestseller list, coupled with the publication of Endless Universe: Beyond The Big Bang, by Paul Steinhardt and Neil Turok, created an interesting opportunity.
I invited Walter, Paul, and Columbia University string theorist Brian Greene to participate in an Edge symposium on Einstein. Walter, Paul, and Brian showed up for the session during the summer of 2007.
A year earlier, in My Einstein, a book of essays by twenty-four leading thinkers, I had asked each of the contributors to share their thoughts on who Einstein was to them. This led me to ask the same questions to the Edge symposium participants.
“I’d say my Einstein surrounded my learning—not learning, really; hearing—in junior high school that there’s this feature of time whereby if you’re moving relative to somebody else, time elapses at a different rate compared to the person who’s stationary,” Brian said. “And thinking to myself, ‘That sounds completely nuts. I really want to understand what this is all about.’ And little by little finally learning what it actually means, and going on from there to try to push the story a little bit further.”
Walter’s response: “Einstein is obviously my father, who as an engineer loved science and instilled that in me, but also has a lot of Einstein’s moral nature to him, and political morality to him. I remember every day growing up, his asking me questions and pushing me in a certain way. One of the things I’ve learned as a biographer, and the first thing you learn, is that as you write about your subject, it’s all about Dad: For Ben Franklin it’s all living up to his father in a certain way. Even for Einstein, a bit—his father’s an engineer. And then the second thing you learn is, even for the biographer it’s all about Dad, and that’s why I wanted to write about Einstein. I shouldn’t say my father’s an Einstein, he’s just an engineer in New Orleans, but that was his aspirational secular saint, and so I wrote the book and dedicated it to my father.”
Paul had a similar response: “One of my earliest memories of childhood was sitting on my father’s knee and his telling me stories about scientists and discovery. He wasn’t a scientist, he was a lawyer, but for some reason he used to tell me stories about scientists and different discoveries they made—I remember stories about Madame Curie and Einstein and others. From that very initial instance, what I wanted to do was be in a field where you got to make discoveries. The thing that always impressed me the more I learned about Einstein was his uncanny ability to take the wealth of phenomena that people were studying at the time, and pick out not only which were the important questions but which were the important questions that were answerable. There are always lots of questions you’d like to answer, but knowing whether or not you have the technology, the mathematical technology, and the right ideas to attack them at the time—that’s a real talent. Einstein had the incredible talent to do that over and over and over again, ahead of any of his contemporaries. So, for me he’s the ultimate discoverer. That is my Einstein.”
Einstein: An Edge Symposium
BRIAN GREENE: When it comes to Albert Einstein, his contributions are of such incredible magnitude that to get inside his head, and even for a moment to get a feel for what it would be like to see the world with such clarity and such insight, would be amazing.
But if I was going to ask him one question, I would probably stick to one a little bit more down to earth, which is: He famously said that when it came to the general theory of relativity, in some sense he wasn’t waiting for the data to show whether it was right or wrong; the theory was so beautiful that it just had to be right. And when the data came in and confirmed it, he claimed he wasn’t even surprised, he in fact famously said that had the data turned out differently, he would have been sorry for the Dear Lord, because the theory was correct. That’s how much faith he had in the theory.
So the question I have is: We many of us, are working on Einstein’s legacy in a sense, which is trying to find the unified theory that he looked for such a long time and never found, and we’ve been pursuing an approach called superstring theory for many years now. And it’s a completely theoretical undertaking. It’s completely mathematical. It has yet to make contact with experimental data. I’d like to ask Einstein what he would think of this approach to unification. Does he see the same kind of beauty, the same kind of elegance, the same kind of powerful incisive ideas in this framework to give him the confidence that he had in the general theory of relativity?
It would be great to have a response from him in that regard, because we don’t know when we’re going to make contact with experimental data. I think most of us in the field absolutely will never have faith that this approach is right until we do make contact with data, but it would be great to have the insight of the Master as to whether he feels that this smells right—that it’s going in the right direction. Many of us think it is, but it would be great to have his insight on that question as well.
WALTER ISAACSON: I was going to ask him the same question Brian asked him, but I’ll extend it now a bit more. Einstein, in the final two decades of his life—and even the final two hours of his life, on his deathbed—is writing equations, very mathematical, trying to do the unified theory that will bring together the various forces of nature into a field-theory approach.
Brian posed the question of whether or not Einstein would approve of this—and I really think he would, because if you look at the maybe twelve serious efforts he made toward a unified theory, they do have so much in common with the mathematics and the mathematical approach that’s being done by superstring theory, including looking at extra dimensions and using the mathematics that way, to try to find the elegant mathematical soluti
on.
That would lead to the next question I have about Einstein, which is, in the first part of his career and, may I posit, the more successful part of his career, he didn’t rely that much on mathematical formalism. Instead, in all of the 1905 papers and in the main thought experiments that set him on the way toward general relativity, culminating in 1915, he had some physical insight. In fact, the people looking at his general theory of relativity call it the mathematical strategy and the physics strategy.
Obviously they’re not totally separate, in their iterative process, but he spent the period from 1905 through at least 1914 almost disparaging mathematics as a clean-up act that people would come along and help him do, once he understood the equivalence of gravity and acceleration or the other great thought experiments he did.
If you look at what he does later in life, with the unified theory, people like Banesh Hoffmann and others who were his collaborators say we had no physical insight to guide us, nothing like the principle of the equivalence of gravity and acceleration, or some other great insight, and instead it became more and more mathematical formalism, without what Einstein called the ground lights that would touch us, as we’ve just said, to physical reality more. And there are some who think—and I kind of feel this way, which is why I’ve adopted this idea—he had used the physical strategy, the physics approach, so much from 1905 to around 1913–1914, and even in the Zurich notebooks where he tries to get general relativity and the equations of gravity right, and he just can’t quite get them, and he’s racing against David Hilbert, who’s a Göttingen mathematician who has the advantage of being a better mathematician but also an added advantage of not being as good of a physicist. Hilbert’s not there worrying about whether it reduces to the Newtonian in the weak field or whatever—he’s just pursuing general covariance as a mathematical strategy in order to get the field equations of gravity. Einstein finally adopts that approach and it puts him there, it makes him succeed through what is a very mathematical strategy, and then for the rest of his life he spends a lot of time on mathematical formalism instead of worrying about the intuitive physics behind everything.
Was that the right approach? Is that what’s happening with string theory? Is that the better way to do it; is that what you have to do? As Einstein said, when he was asked about this: That’s the way you have to approach things now; we don’t have any blinding new physics insight.
Finally the bigger question is, when he fights—and I do think his quest for a unified theory comes out of his discomfort with quantum mechanics—when he is pushing against the people in the realm of quantum mechanics, they push back, and they say things like, “Well, we’re just doing what you used to do; we’re questioning every assumption. We’re saying that unless you can observe something there’s no reason to posit that it exists.” Einstein is saying, “Yes, but that doesn’t make sense now.” They respond, “Well, you always questioned authority and questioned everything unless you could actually observe it, and now you’re resisting us.”
Einstein said, “Well, to punish me for my contempt for authority, fate has turned me into an authority myself.” I’m no longer quite as rebellious, is what he’s saying. So why is it that he becomes in some ways more defensive of the classical order and less rebellious, even as he’s trying to pursue the unified theory?
PAUL STEINHARDT: The question I have about Einstein relates to the one Brian raised, but with a twist, because I see what has been happening in theoretical physics in the last thirty years, and especially in the last few years, maybe from a slightly different point of view.
Over the last thirty years, there have been grand ideas that have emerged in theoretical physics that were meant to simplify our understanding of the universe. One is the idea of inflation—the idea that there was a period of very rapid expansion that smoothed and flattened the universe and which explains why, when we look out anywhere in space, it looks almost the same everywhere. And it is, of course, based on Einstein’s general theory of relativity and relates directly to his introduction of the cosmological constant back in 1917, but elaborated in a way that this rapid expansion would only occur in the early universe and not in the later universe. Just to explain why the universe is the same, or looks the same, almost everywhere.
The other grand idea that has been developing is the one Brian has written so elegantly about, which is the idea of string theory—that everything in nature is made of quantum vibrating strings, and that we can derive a simple unified theory to explain all the physical laws that we see.
The hope was that string theory would explain the microphysical world and inflation would explain the macrophysical world.
What have we learned from these two grand theories, inflation and string theory? Well, in the last few years, especially in the last decade, we’ve learned that—at least to my way of reckoning things—neither of them is really delivering on their promise. It turns out inflation doesn’t do what we originally thought it did back when it was introduced in the 1980s. It doesn’t take an original initially complicated inhomogeneous, nonuniform, curved and warped universe and flatten it out everywhere—and leave it with a universe which is full of matter that we see, which is then smoothed and flat. Instead, what inflation does, once it takes hold, is continue to make a more and more inflating universe, only occasionally leaving behind a few pockets of universe that have matter we would recognize and that might be inhabitable.
And in fact among those pockets, it seems that the pockets that would look like the ones we observe would be exceedingly rare. So whereas inflation was designed to explain why the universe is as uniform as it is, and why that’s a likely occurrence, it seems the theory is leading us to a point of view where with inflation we’re unlikely to find pockets of the universe that look as smooth and flat as we observe.
Similarly, the hope for string theory was that it would uniquely explain why the laws of physics are what they are. But developments over the last few years suggest that string theory doesn’t make a unique prediction for the physical laws—there might be a googol, or many googols, of possibilities. And the ones we happen to observe are not particularly likely—at least there’s no reason why they should be likely.
So a key conclusion, according to the current view of string theory and inflationary theory, is that the fundamental nature of the universe is random. Although the universe seems to be remarkably uniform everywhere as far as we can see, our leading theories currently suggest that the conditions we observe are actually very rare and unlikely phenomena in the universe entire. And I wonder what Einstein would have thought about that. I wonder if he would have found that idea—that is, a theory of this type—to be acceptable. My own point of view is that we have to change one or both of these two key components of our understanding of the universe. We either have to dramatically revise them or we have to overhaul them entirely, replace them with something that combines to make a powerful theory that really does explain, in a powerful way, why the universe is the way that it is.
ISAACSON: Why is there such a personal theological argument—I can see it between the Sam Harrises and the Dawkinses and Christopher Hitchens versus those who are strong believers—that when people start debating string theory, their faces turn red.
STEINHARDT: I think it’s for the reason that I was beginning to raise. In my view, and in the eyes of many others, fundamental theory has crashed at the moment. Instead of delivering what it was supposed to deliver—a simple explanation of why the masses of particles and their interactions are what they are—we get instead the idea that string theory allows googols of possibilities and there’s no particular reason for the properties we actually observe. They have been selected by chance. In fact, most of the universe has different properties. So the question is, Is that a satisfactory explanation of the laws of physics? In my own view, if I had walked in the door with a theory not called string theory and said that it’s consistent with the observed laws of nature but, by the way, it also gives
a googol other possibilities, I doubt I would have been able to say another sentence. I wouldn’t have been taken seriously.
GREENE: You really think that? I don’t mean to get technical, but take the standard model of particle physics, which is the quantum field theory that people have developed over the course of a number of decades and that we generally view as the most solid, pinnacle achievement of particle physics. When you look at the framework within which the standard model of particle physics sits—namely, relativistic quantum field theory—you do find that there are a googol, if not more, possible universes that that framework is capable of describing. The masses of the particles can be changed arbitrarily and the theory still makes sense, it’s internally consistent; you can change the strengths of the forces, the strengths of the coupling constants.
So if you see the standard model, the one we all think is so spectacular, within the landscape of theories that that framework can give rise to, it seems to me that when you walk in the door and you say, “I’ve got this theory called the standard model to describe all physics,” isn’t everybody excited? If I were to use the same benchmark for judging it, you’d think I would ignore it as well, since it actually is part of a family of theories that can describe a googol of different universes. So how is that any worse than string theory?
STEINHARDT: Well, I think there’s a key difference, which is that no one believes that the standard model is the ultimate theory, and string theory is claiming to be the ultimate theory.
GREENE: Oh, I think we should put claims of that sort—
STEINHARDT: But the question was raised, Why are people upset about it? And the answer is, Because whether you personally believe it or not, string theory has been advertised as being the ultimate theory from which we should be able to understand—
GREENE: I guess I would say it’s unfortunate that people get worked up over that kind of advertising. If you look at the history of string theory, I agree with you; there was a time when people thought this could be it—the final theory that would describe everything. In fact, it still may be it.
The Universe_Leading Scientists Explore the Origin, Mysteries, and Future of the Cosmos Page 24
