Alan Lightman: Einstein's Relativity is no Light Weight
Alan Lightman
Generally considered one of the most influential physicists in history, Albert Einstein’s (1879 - 1955) groundbreaking theories reshaped the scientific community's view and understanding of the universe. He developed the special and general theories of relativity and won the Nobel Prize for Physics in 1921 for his explanation of the photoelectric effect.
Alan Lightman is a novelist, essayist, physicist and educator, and his books have been translated into thirty languages. He won the 1990 Association of American Publishers award for Origins and was runner-up for the PEN New England/Winship Award for Einstein's Dreams. Published in the UK in 2000, The Diagnosis was shortlisted for the National Book Award. His latest novel, Ghost, was published by Vintage in July 2007.
Alan Lightman is Adjunct Professor of Humanities and Senior Lecturer in physics at the Massachusetts Institute of Technology (MIT).
The following interview was transcribed and edited from Simply Charly's Culture Insight podcast. To listen to it, click here.
Q: Can you begin by explaining the difference between Einstein's general and special relativity?
A: General relativity is a theory of gravity, and an underpinning of it is that gravity is equivalent to acceleration. So when you deal with accelerated observers, you are, in effect, dealing with gravity.
An accelerated observer is someone who doesn't go at constant speed. If you're going down the highway in your car, and you're going at a constant speed, you can't tell you're moving. You don't get any jerks or pulls. But if you push your foot down on the accelerator, you feel a jerk, and that's an acceleration. You are changing your speed, by going from 30 mph to 35 mph.
So general relativity deals with accelerated observers and gravity, and special relativity deals with constant velocity observers.
Q: How does a physicist like yourself apply Einstein's Theory of Relativity to modern science?
A: Well, it's interesting. Special relativity is not really a theory of a force. It's a theory of the stage in which all forces act. It's a theory of how time and space behave. And since time and space enter into every theory of physics, special relativity is the backdrop for every modern theory of science.
You can't invent a new theory of physics and not obey the laws of special relativity. Special relativity must be built into every new law of physics; that is, it represents our modern understanding of the way that time and space behave, the way that measurements of time and space are made. It's like the air that physicists breathe - it's everywhere.
Q: What were Einstein's major contributions to physics, besides his Theory of Relativity?
A: Well, Einstein wrote three other very important papers in 1905, for any of which he could have won the Nobel Prize.
One was a theory that was the basis, the beginning of quantum physics, which is the other major revolution in the 20th century physics, besides relativity theory. And Einstein proposed that light is not a continuous stream of energy, as it appears to be, but actually comes in packets of energy, little marbles of energy, you might say. And that was a very important contribution he made to physics.
Two other important papers that he wrote in 1905 dealt with the understanding of molecular motion, and the way that little particles in a fluid will dance around. If you look at them with a magnifying glass and put a little dye in there for color, you'll see them jumping around a little bit.
Einstein was able to show that the way they jump around is exactly what you would predict, as if the fluid consisted of atoms and molecules. He was actually able to calculate the sizes of atoms and molecules from the observations of how much the fluid jiggles when you're looking at it.
And this was really the first proof that atoms and molecules existed. Atoms and molecules had been proposed since the ancient Greeks. For two thousand years, they proposed that there was some tiny constituent of all matter; that all matter was made out of some smallest unit that could not be further subdivided. And they call that the atom.
But there was no real evidence for atoms; it was just a theory. Einstein related the observations of fluids, the way that little particles in fluids jump around, to the existence of atoms and molecules. And by observing fluids, you could then infer the reality of atoms and molecules.
One of the interesting facts about Einstein is that he was not all theoretical. He had a practical side to him. A lot of theoretical physicists will only construct their theories and not worry too much about how they relate to observations or to experiment. But Einstein was well-versed in experiments, as well; he knew what the observations were of fluids under a magnifying glass and he referred to that in his paper.
And in a number of his other papers, he related the theories that he was working out to detailed results from experiments. So, he brought the two together. And after all, he worked for several years in the Swiss Patent Office, where he was examining new inventions, and a guy like that has to be very practically inclined. So Einstein had this practical, experimental side, as well as the lofty, theoretical side.
Q: He had to be very patient to await the results of these experiments, to bear out his theories, wouldn't you say? Wasn't one of his theories confirmed as late as 1919?
A: The test of general relativity was done in 1919, but there were actually tests of special relativity before then. Actually, the first test of special relativity ruled it out. One of the predictions of special relativity was how the mass of a subatomic particle should increase with speed, and this was actually measured in experiments done, I think, around 1907 or 1908. The initial experiments show that special relativity was wrong. They were more in accordance with alternative theories, rather than with Einstein's theory.
Einstein's reaction was that the experiments were wrong, not his theory, because the theory was too beautiful. And even though I said that Einstein was practically minded, he did realize that experiments could sometimes be an error, and he put great stock in theories that came from general principles.
He didn't like theories in physics where all of the parameters were adjusted to fit particular observations. He preferred theories that started from sweeping, philosophical principles, and then deduced reality from that. So, when the initial experiments done in 1907 and 1908 - I think one of them was by a physicist named Kauffman in Germany - disagreed with his theory, he said, "Let's wait a while for new experiments." And, sure enough, within the next few years, there were new experiments that were in agreement and confirmed the Theory of Special Relativity.
His Theory of General Relativity and his Theory of Gravity made a prediction about how much light should be deflected by the sun. In general relativity, all energy is affected by gravity - not just particles with mass, but light beams as well. And his theory predicted how much a light ray passing near the surface of the sun should be deflected by the gravity of the sun. That was actually measured in 1919 by a British physicist, Sir Arthur Eddington, and the measured result agreed with Einstein's Theory of General Relativity.
That's actually when Einstein became known to the public. He was not known for his Theory of Special Relativity. In 1919, a year after World War I ended, the world was grieving its losses and the inhumanity of people toward other people. They were looking for some hero, some pure scientific kind of person who had no political aims. Everybody latched onto Einstein in 1919, when the experiments by Eddington confirmed his Theory of General Relativity. There were headlines all over the world, and that's when Einstein became a well-known, public figure.
Q: Today quantum physics seems to be the prevailing model that explains much of the physical world around us. Why did Einstein have such a difficult time accepting quantum mechanics?
A: Einstein didn't like the uncertainty in quantum mechanics. He didn't like the idea that you could not make definite predictions, that you had to only give the probability for something to happen. He believed that nature was definite, that if you understood nature well enough, that by knowing the present you could predict the future, that it was all just a deterministic system.
One of the fundamental ideas of quantum physics is that, even in principle, you can't make definite predictions about the future from the present. You can only say, there's a certain probability for A to happen, there's another probability for B to happen, there's another probability for C to happen. You know that all the probabilities must add up to a hundred percent, but you don't know exactly how much of A, how much of B, and how much of C is going to happen. And Einstein did not like that uncertainty, that lack of determinism.
So his resistance to quantum physics was really a philosophical resistance. It was not based upon any scientific reason.
Q: Toward the end of his life, he was working on a Theory of Everything?
A: He didn't call it that. He called it a unified theory, and it was a very specific theory. He was trying to unify the force of electricity and magnetism with the force of gravity, and those were the two principle forces that were known in the 1920s and early 1930s. He did not call it a Theory of Everything.
Q: Are we getting any closer to what Einstein was striving for?
A: There are four basic forces. There's an electromagnetic force, which causes iron filings to be moved by a magnet. There's a gravitational force, and there are two kinds of nuclear forces, which we call a strong and a weak nuclear force. And we've already succeeded in unifying the electromagnetic force with the weak nuclear force. That unification was done in the late 1960s, leaving three independent forces.
We have a pretty good theory now, called quantum chromodynamics, which unifies the electroweak force with the strong nuclear force. So it's just the gravitational force that remains to be unified, and there are some ideas about how to do that.
So I think that physicists are moving in the direction of having a single force that nature obeys, and this has been the Holy Grail of physics, I think, since Aristotle: to try to find the smallest number of forces, the smallest number of particles, the smallest number of free parameters which could explain everything. If a physicist can explain phenomena in terms of three principles instead of five; or three parameters instead of five; he or she feels like progress has been made.
A physicist would like the situation to be such that the general principles of physics, like the principle that all observers, see the same laws of physics, no matter what their motion is; they would like to see a few general principles which are not mathematical, which can be stated in words, be able to explain all the masses of particles, all the forces that we see in nature, everything. It's a very platonic view of the universe, and that's what physicists would most like.
One of the things that bothers many physicists about string theory today is that there seem to be an infinite number of different possibilities and, parameters, and a lot of different versions of string theory. This is the opposite of the dream of simplicity - of having no free parameters, but one principle that explains everything. The string theory today, which we've learned in the last ten years, has gone in the opposite direction; it has too many possibilities, too many parameters that can be adjusted. And this is what concerns some physicists about string theory.
Q: Why do you think string theory seduces so many brilliant minds?
A: In the 1980s, it looked very hopeful. It did offer the potential of unifying gravity with the other three forces, and a lot of brilliant minds, like Edward Witten at Princeton, did put their money in string theory and their hours during the night, and so on.
But in the 1990s we discovered that, instead of there being one solution to string theory, there are many different versions of string theory,and there's no way to decide which one is the right one, if any. That was not known until the 1990s, and that's very discouraging to some physicists.
Also, we haven't been able to make any definite predictions with string theory. It's like having a hundred dollar bill in a poor neighborhood. You can't cash it.
Q: Many physicists are excited about the new Hadron Collider in Switzerland. Can you give us your view on what we might expect from it?
A: Some of the new theories of particles and forces - I would say, many of them - make predictions of certain kinds of particles that we should observe, and some of these particles are very short-lived. They come into existence and then annihilate very, very quickly. They're heavy, so it requires a lot of energy to create them.
We think that the new Hadron Collider in Geneva will have enough energy to make some of these predicted particles. And so, we're hoping to see them. That will confirm some of our modern theories of particle physics.
In particular, and one thing that Frank Wilczek has worked on, is the existence - as some of our theories predict - of a particle called a Higgs particle. That particle, and the energy field that surrounds it, is supposed to have the property to have created the masses of all the other particles. It gives empty space a kind of viscosity or stickiness, like molasses. It produces a molasses in empty space so that other particles have a drag when they go through this energy field of molasses, and that drag is what gives other particles their mass; why they're not all massless, like the light particle, the photon.
And we should observe the Higgs particles, if our theories are correct. If we don't observe the Higgs particles, then we've also learned something very important, and we'll have to throw out some of our theories.
The energy of the Large Hadron Collider is at least ten times the energy of the highest energy that we've created before. It's amazing that we were able to create such high energy. And when I say energy, I mean energy density. The total amount of energy in one of those giant particle accelerators is not that great. What's impressive is that it's able to focus a lot of energy on a single particle, a single subatomic particle.
Q: Seems like every few decades or so, we are building a bigger collider to arrive at, or determine, the basic, most fundamental particles of matter. Will we ever reach an end to this?
A: I think that we'll keep building new colliders; I mean, it's getting more and more expensive.
Long ago, I would say, fifty years ago, or at least forty years ago, physics passed the point where a single observer or even a single university could afford to finance a project. A hundred years ago, or even fifty years ago, great breakthroughs in physics could be made by one or two people doing an experiment they could set up in their laboratory.
Those days have passed, and if we want to be at the frontier of experimental physics, we now need huge - and usually expensive - equipment, which requires the cooperation of many institutions and sometimes even many governments. But I think that we will continue to try to build bigger and bigger particle accelerators.
About fifteen years ago, we were building a big accelerator in the United States called the superconducting super collider. It was going to be in Texas, and we actually put a couple of billion dollars into it before it was cancelled by Congress. I know that we're going through a global recession right now, and probably for maybe ten years, there'll be cutbacks in expenditures.
But I believe that humankind will continue to put money into experiments at the frontiers of science. And even in biology, when you learn all the genes in a chromosome, you know those experiments are getting to be more and more expensive, and beyond the capability of a single laboratory.
This seems to be the trend in science. It's what you might call a big science. The days of little science, when a few people could do an important experiment themselves, are gone. Now, most of the science at the cutting edge of astronomy, physics, biology, and chemistry is done by large teams of people, because a lot of money is involved. And when you read a paper now in the Physical Review, fifty or a hundred names will be listed as the paper's co-authors.
I always wonder what this does to the motivation of individual scientists. If you're a single scientist, you're very smart, you're graduating with a Ph.D., and you want to make your mark in the world, what does it do to your motivation and your ambition when you become one of a team of a hundred people? So I worry about the motivation for single scientists who want to make their mark.
It's not the same in theoretical physics or theoretical science. It's still true that in theoretical science, where your only tools are paper and pencil, and maybe a computer, great breakthroughs can be made by one or two people. So it's only in experimental science where you require these big machines, satellites flying above the earth, the gene sequencers, and so on, that you need big teams of scientists.
Q: What are you currently working on?
A: I stopped doing research in physics about fifteen years ago. I started my career as a physicist, and then I began writing, and there was about a ten-year period, from maybe the late 1970s to about 1990, where I was trying to do both; to be a physicist and a writer, and burning the candles at both ends. I eventually felt that I couldn't do it any longer.
Around the age of forty or so, I began slowing down on my science. I was keenly aware that I was past my peak, and I could have continued as a research scientist, but I had this other interest, which was writing, and I started putting more time into that. So I don't do scientific research any more.
Q: Talk about your book, Einstein's Dreams, and how that developed.
A: Einstein's Dreams is the first full-length fiction that I wrote. I wrote it mostly in the summer and fall of 1991, and it is a book that imagines what Einstein might have been dreaming about when he was working on his Theory of Relativity.
It's all fictional. There are very few recorded dreams that Einstein actually had, so it's not based on any fact. But Einstein was in his mid-twenties, working in the Patent Office in Berne, Switzerland, and my book consists of about thirty nights of dreaming, and in each night he imagines that time might behave in a different way.
In one dream, he imagines that time is circular, so we keep repeating our actions. In another dream, he imagines that we can travel backwards in time, and change the future. And in another dream, he imagines that cause and effect relationships are reversed; that effect comes first, and then cause.
I think the way the book came to me, although it's always hard to say where an idea comes from, was that the title came to me first. I've always, since childhood, been interested in both the arts and the sciences. When I was twelve years old, I wrote poetry and I also built rockets that I fired into my neighbor's windows.
I've been interested, always, in the tension between the rational and the irrational, or between the scientific way of looking at the world and the artistic. And of course, it's not black and white. There are scientists who, at times, act like artists, and vice versa. But it's a pretty good way of dividing your friends: the people who are rational and always reasoning through things, and your other friends, who go more by their instincts and their guts.
When the title, Einstein's Dreams, came to me in the summer of 1991, Einstein represented our rational side and dreams represented our more intuitive, or irrational side, I felt there was a lot of energy in the juxtaposition of those two words. The idea occurred to me to follow through with that and to write a book about that period of Einstein's life when he was working on the Theory of Relativity, and to see what his dreams might have been like. The book came about very quickly. I think I spent about six months on it. It was like the book wrote itself.
When the title, Einstein's Dreams, came to me in the summer of 1991, Einstein represented our rational side and dreams represented our more intuitive, or irrational side, I felt there was a lot of energy in the juxtaposition of those two words. The idea occurred to me to follow through with that and to write a book about that period of Einstein's life when he was working on the Theory of Relativity, and to see what his dreams might have been like. The book came about very quickly. I think I spent about six months on it. It was like the book wrote itself.
