Physicist Steven Weinberg—The Great Unifier

Wednesday, May 01, 2002

Steven Weinberg
Photograph by Jeff Wilson
Steven Weinberg shared the 1979 Nobel Prize in Physics for a landmark act of unification: He found an underlying similarity between two of nature's four forces, electromagnetism and the weak force. Now at the University of Texas at Austin, he has a dozen honorary doctoral degrees to his name as well as several best-selling books. He even appears in Bartlett's Familiar Quotations. "The more the universe seems comprehensible, the more it also seems pointless," he wrote in his book The First Three Minutes. He continues to defend this view in his latest work, Facing Up: Science and its Cultural Adversaries (Harvard University Press, 2001.) Weinberg discussed the limits of knowledge with associate editor Josie Glausiusz.

You've worked towards a "final theory" of physics that would unify all of nature's forces. What would such a theory consist of?
A final theory would be a scientific principle which explains gravity and all the other forces of Nature, explains why the quarks and the electrons and the neutrinos and all those other particles have the properties they have. It would be at the end of the chain of explanations.

How close are we to finding such a theory?
Damned if I know. It really could be tomorrow morning. It could be some very bright young person whom no one has ever heard of before, who puts an article on the web archive we all look at every morning (http://arXiv.org). Or it could be more than a century away. I think the history of the last thirty years has not been very encouraging. Starting in the early 1980's, there has been a hope that something like string theory would provide the key. But it is so far just a hope.

How could a final theory help us understand the origin and fate of the universe?
When the universe was three minutes old, there were nuclear reactions that produced the lightest chemical elements, with which the stars began their lifetime. We can follow the story back a little further than that, to perhaps the first second. When you try to push the story back much beyond that, you get the conditions where the density of energy is so high that you can no longer ignore the quantum nature of gravity. And we don't have a quantum theory of gravity that is mathematically consistent. So that in itself is a barrier. We can't look back in time beyond a certain moment.

As far as the future is concerned, the universe is expanding and getting colder, and is easier to describe as time passes. But there are some big questions that we don't know. For instance, recent observations indicate that the expansion of the Universe is accelerating, and this is related to an energy density in empty space which has a negative pressure and creates an accelerated expansion of the Universe rather than the slowing down which we would have expected because of gravity. The nature of this so-called dark energy is a fundamental question of physics

Will finding a final theory bring an end to science?
No. Because most of the problems of science involve complexity, and just knowing the fundamental principles doesn't solve those problems. For example, we already know all the principles that govern the atmosphere of the earth and the oceans. We know the laws of hydrodynamics and aerodynamics. We understand the chemistry of the elements and the air and the oceans and the earth. But we can't predict the weather with great accuracy, and we certainly can't predict it more than a few weeks in advance. It also probably won't help at all with understanding consciousness.

How has your research helped further the search for a final theory?
The research for which I'm probably best known has to do with the unification of the electromagnetic forces with another class of forces, the so-called "weak" nuclear forces which are responsible for some kinds of radioactivity and for some of the processes that produce the energy of the stars. The electro-weak theory, which several people contributed to, gave us a unified and mathematically consistent theory of both electromagnetism and the weak forces, so it was a big improvement.

What's the unifying theme of Facing Up?
All of the essays in the book deal with the necessity of facing up to the discovery that we live in a world governed by impersonal forces in which human beings don't play any particular important role. But I certainly don't mean we can't make a point for ourselves. If we decide for ourselves that we value things, there's nothing in the laws of nature that says we shouldn't do that.

Who are the cultural adversaries of science?
One obvious adversary is religion, which teaches that we are actors playing a part set out by God and that we have a divine destiny. Well, I don't agree with that! Other adversaries are those in the academic world who take a relativistic view of the truth.

I heard a lecture by someone who was talking about the pre-Columbian-American views about the nature of the Milky Way, and she was actually rather annoyed when I said, "But they were wrong," because she didn't feel that 'wrong' was a word that should be applied to beliefs that are part of a culture. Well, I don't think one can say that their marriage practices are wrong and I don't think one can say that their music is wrong, but I do think that one can say that their ideas about the universe are wrong.

But that view is unpopular in many parts of the academic world, in which science is seen as just another social construction which is no more privileged than religion or magic or anything else. This is partly a debate with people who don't like science at all—postmodernists who think of science as being "Western" and "masculine" and "Imperialist." The varieties of nonsense in the world are fortunately so endless as to provide a never-ending stream of humor.

What did you mean when you said that the universe "seems pointless"?
Ever since people started thinking systematically about the world, there has been a widespread impression that the universe exists partly to serve the interests of humanity. That is, that nature is arranged to make it possible for human beings to be here. Galen, the Greek medical scientist and philosopher, said, "The reason the sun is where it is relative to the earth is so that the earth would not be too hot or too cold for us." That is a very crude example, but there is a general impression that we somehow have a special significance built into nature. I don't think that's true.

By the way, that quotation from The First Three Minutes is followed by another paragraph which says, "But if there is no solace in the fruits of our research, there is at least some consolation in the research itself. Men and women are not content to comfort themselves with tales of gods and giants and confine their thoughts to their daily affairs of life. They also build telescopes and satellites and accelerators, and sit at their desks for endless hours working up the meaning of the data they gather. The effort to understand the Universe is one of the very few things that lifts human life a little above the level of farce and gives it some of the grace of tragedy."

What do you think of this latest creationist push to teach so-called "intelligent design" alongside evolution in schools?
It's very clever politically. Unfortunately, it takes advantage of a very admirable American trait of wanting to see all points of view presented. But there's a limit to that in school. I mean, we don't allow people who teach geography to teach that the world is flat. People who teach science, it seems to me, have to teach what is the scientific consensus.

This, by the way, is what the courts do when they hear expert testimony. A judge will not allow someone to come in and present evidence based on astrology or clairvoyance. The judge says, "Well, no, that's not science, and the definition of science is what is accepted by the scientific community." Intelligent design isn't, creationism isn't, and it therefore has no place in the science curriculum, any more than the flat earth does.

Do you think science is rendering religion obsolete?
No. Because a lot of the motivation for religion has nothing to do with a theory of nature or an understanding of the natural world. It's part of the human personality to be horrified at the idea of our extinction at death, to wish that we could go on living and be rejoined with the people we love. I don't think science has anything to offer like that.

What science does do is show that as you understand more and more of the universe, you do not need the concept of a divine intervention to explain what you see. The greatest step in that direction I think was Darwin's theory of evolution by natural selection, which showed how the wonderful properties of advanced forms of life, like human beings, could have arisen without any preconceived divine plan. As you learn more and more about the Universe, you see less and less of the hand of God in guiding it.

In Facing Up you write of the human dream of Utopia. What is your vision of the ideal world?
There's no prescription for an ideal society, and great harm is done by people who offer prescriptions. There are however suggestions that I think can be made about improving our society. I think it should be much more egalitarian. I think there should be less emphasis on private goods and more emphasis on public goods—things that can't be provided by the free market. Fundamental scientific research obviously is one. The arts. Drug rehabilitation centers. Meat inspection. All sorts of things that we don't spend enough on, and that are more important than things we do spend a lot of money on, like flat screen television or suburban utility vehicles.

To what do you attribute your own sense of happiness?
It's been very happy because I have people I love, my wife and daughter, very intensely. I have managed to escape plagues and wars. I've lived my life in America, a country that has not been under direct attack except for minor episodes. And obviously, I've been lucky enough to be in a country that's able to support the kind of work I love to do.

When I was young, trying to work to make money to go to college, I had a lot of jobs which I didn't like. I was a waiter. I was a caddie. I was a bookkeeper in a company in Manhattan. My first technical job was at Bell Laboratories between my junior and senior years of college. And they actually paid me to sit around thinking and designing circuits. That was wonderful! And ever since then, I've always been able to enjoy the work for which I'm paid. It's a wonderful thing in your life not to look forward to weekends, but to really enjoy work as one of the great things in your life. Not many people are as fortunate as that.
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