Apr 15, 2010
I live my life, plan and do, worry and wonder. But whenever I slow down, step back, and ponder what it’s all about, I go to the laws of nature. Down deep, what are they? What makes them laws? And are they necessary, like the laws of logic? The universe and humanity—our origin and existence—depend on these laws. But where do the laws of nature come from?
Whenever I have a deep question of science, one person I turn to is Sir Martin Rees, the United Kingdom’s astronomer royal. When I express my uncertainty of “what we really mean by laws,” Rees is reassuring.
“You’re not the first to be puzzled,” he tells me. “One of Einstein’s most hackneyed sayings is, ‘The most incomprehensible thing about the universe is that it is comprehensible.’ What Einstein meant is that the laws of nature seem to apply not just here on earth, but everywhere in the universe. We could imagine a universe where there were no laws at all, completely anarchic, every atom being different. And were that the case, we’d make no progress at all in making sense of the external world.”
Laws are regularities that work everywhere the same. That may seem obvious, but when I think about it, it’s astonishing. (Nothing I ever do is everywhere the same!) If there were no laws, we could understand nothing. But we understand a great deal. Regularities, Rees says, makes science possible.
“The progress of science has been understanding that there are patterns in nature and discerning successive unifications of these patterns,” he says. “And this, of course, makes it possible to make predictions, which means that we don’t need to remember so much—we needn’t record the fall of every apple because we know how it happens.”
I ask about the hierarchical nature of laws operating at different levels of science. “One sometimes thinks of them with physics [most fundamental] at the bottom, then chemistry, then cell biology, organism biology, and all the way up to the social sciences, perhaps with economics in the penthouse as it were,” Rees says. “But if one thinks of this hierarchy like the different levels in a building, that analogy is false in a certain sense because in a building, an insecure foundation imperils what happens above, whereas in the case of different levels of the scientific hierarchy, the laws operating at each level are independent. Biologists trying to explain animal behavior don’t analyze it in terms of physics. Each level in science has its own autonomous concepts.”
In the hierarchy of laws, the most fundamental, the bottom layer as it were, is physics. Here’s how Nobel laureate Steven Weinberg, a founder of the so-called “standard model” of fundamental particles and forces, thinks about laws.
“It’s actually a great discovery that nature is governed by laws,” Weinberg begins. “This is something that wasn’t apparent for a long time. In fact, the idea of laws of nature was rejected by an Islamic philosopher, Abu Hamid al-Ghazali [in The Incoherence of the Philosophers], in the late 11th century on the grounds that the very concept put God in chains. Things happen not because there are laws of nature, but because God wants them to happen that way. Of course, that attitude makes science difficult.”
There are all kinds of laws, Weinberg continues. “Many laws are derived from deeper laws. Some of them are purely empirical; we don’t know why they work. But most of the ones that have been well tested and accepted are understood based on deeper laws.”
He goes on: “The deepest laws that we have at present, the laws from which all other laws can be deduced insofar as they can be deduced from anything, are the laws of the ‘standard model,’ a set of equations governing quantum fields which manifest themselves as various particles, electrons, quarks, and photons. The next big step is to explain: Why the standard model the way it is? It’s not a final law. What’s underneath the standard model? We don’t know.”
The search for deeper laws, more fundamental laws, is the driving force of physics. Weinberg’s quest is for a “final theory.” But even then, even with a “final theory,” questions will remain, he says. Is ours the only universe that can contain human beings? And, ultimately, why that “final theory,” rather than some other?
Freeman Dyson, one of world’s most innovative scientists, describes the laws of physics as mostly “very simple and beautiful equations which are, in some sense, totally precise and describe what nature does.” He muses that, “Somehow nature does what the equations say. That’s something quite unique. There’s nothing like that in biology; there’s nothing like that in chemistry or anywhere else. In the rest of science, we have what we call ‘emergent laws,’ which are laws that arise out of complicated structures where the structure as a whole has a well-recognizable behavior; for example, the laws of evolution in biology. You can’t write down an equation for evolution, but you know what it means. It tells you roughly how things go when multitudes of species compete with one another. These are definitely laws, but they’re not in the same category as the laws of physics. They’re some sort of abstraction arising out of a whole multitude of facts.”
I pose the following to Dyson: “Some philosophers argue that even though the equations of physics work, they don’t represent reality. They’re just human inventions which impose artificial constructs on reality. As for the real reality, humans will never access it.”
“Of course that may be true,” Dyson responds. “We were monkeys who only just recently came down from trees. It’s amazing how well we are doing, but I don’t regard what we have now as final. I wouldn’t be at all surprised if it turns out that all our science is very, very partial, and there are whole worlds of existence out there of which we haven’t an inkling. In 1,000 years, today’s science will look extremely primitive.”
I contrast some physicists and religious philosophers in that the former would claim that laws are the fundamental reality and therefore we can do away with archaic gods, whereas the latter would claim that these laws reflect the mind of God.
“Of course, I’m not a philosopher,” says Dyson, “but if you wanted to say what I am, I would say I’m a dualist in a way. I think there is a physical world and there is a mental world, and they’re very different. And we understand the physical world extremely well, but we understand the mental world hardly at all. All these questions about God and the nature of consciousness and so on, these belong to the mental world, and we’re not close to answering them. I think the laws of physics are fine as far as they go. But there’s no reason to imagine that that’s all there is. We have evidence that there are mental things which are outside the scope of physics, but we don’t have the tools really to grasp them. I prefer that the laws are independent, that the mental world has its own autonomy. But then, of course, that’s my prejudice. God may turn out to disagree with me, as he often has in the past.”
To Dyson, science is nowhere near a “final theory,” and what we know today will look “primitive” in the future. He rejects the claim that the laws of physics are “all there is,” and he asserts that there is a kind of mental world that is very different from the physical world.
I’m still at sea: Are the laws of nature “special entities”? Somehow “out there”?
Peter Atkins, a tough-minded atheist who brooks no mystical, metaphysical, or mental meaning in laws, says that, “One has to be careful about what one means by a scientific law. My view is that a scientific law is just a summary of observation. So it’s a summary of behavior. For example, one can make detailed observations of electrons, and when one finds consistency of behavior, one can encapsulate that consistency in a statement which, traditionally, we call a law.”
This means, in essence, that laws are not things existing in their own rights. “Everything begins with experiments, with observations, which enable you to formulate a summary of behavior, the law,” Atkins says. “Then you make a guess about what the reason might be. You call that a hypothesis. And then if your hypothesis rings true, you construct a theory, which is often a mathematically rigid theory.”
Atkins’ thinking empowers data, elevates experimentation—and dethrones “laws” from its lofty perch.
But what about the laws of physics? Aren’t they “necessary”?
Physicist Lee Smolin says that “there are two very different kinds of claims about laws in the history of philosophy and which face us now.” In essence, laws are either necessary or contingent. The necessary claim, Smolin says, is that “the ultimate truth about reality is timeless. The ultimate laws don’t come from anywhere; they just are. The tradition of looking for explanation of the laws in terms of necessary relations is closely connected with the idea that the laws are mathematical because this is the belief that mathematics is the study of necessary relationships.”
The competing claim, Smolin continues, is that laws are contingent. “What’s most fundamental is what’s bound in time,” he says. “Time is fundamental, time always exists, and time is change. And if you go with this model, then where do the laws of nature come from? They come from the past. They are the results of processes that happened in the past.”
Smolin believes that the problems in quantum gravity and cosmology “push us in this direction.” This means, he says, that “the explanation for why the laws are the way they are is because they evolve from the past. Whether there’s a meta-law or not, the laws that we observe now were not true before the big bang—they were different, and they were different again before the big bang of the previous universe, and so forth.” Smolin argues for the evolution of the laws of physics, which, he continues, “suggests reproduction of universes, reproduction of space and time. Maybe space itself is the result of a process of evolution. Maybe a universe that gets very large is able to propagate itself more successfully. With this view, no laws are necessary; all are contingent.”
Laws evolving so that their universes can grow larger and propagate better? Perhaps a bit much. Although such speculations are almost always wrong, I applaud them (if not quackery) because they challenge current belief and impel us over the horizon.
But still I ask: In their ultimate essence, at their core, what are these laws of nature?
Bas van Fraassen, a philosopher of science, believes there is a deep dilemma about physical laws. In the 17th century, he says, “the concept of law was very important both in philosophy and in science, just as the concept of law was being taken away from theology. Laws were no longer the commands of God, but some sort of secular equivalent was being kept because certain principles looked so basic that they were called laws. And the concept of law was still connected very closely with the idea of natural necessity—necessity in nature.”
Van Fraassen says this view—that laws could not be otherwise (which came from the Aristotelian tradition)—is not the way scientists reason today. “They think in terms of models and symmetries, or symmetry breaking, about very basic structures,” he says. “They’re not talking about, ‘What is necessity in nature?’ It’s only the metaphysicians who are doing that now.” Sometimes, empirical scientists use the word “law,” van Fraassen says, “but they do so as an honorary epithet.”
As he explains: “The notion of law implies necessity. It’s supposed to explain why things have to happen the way they do. The empiricist says things just happen. There’s nothing that explains why they have to happen the way they do.”
So, summing up, what’s real? What’s fundamental?
I must conclude that to speak of the “laws” of nature may betray archaic thinking. There are regularities in nature, things that are or work the same—always, everywhere—across the universe just like across your kitchen. But because they are not “necessary”—in that it is not impossible for these regularities to be otherwise—they cannot be “laws.” And they might even change—subtly in our universe or massively between different universes.
Regularities are real, known by observation and testing. But what we call “laws” may be human constructions, our peculiar sense of order imposed on an indifferent reality.
But why the regularities? Why is it that all is always and everywhere the same? Is something here hidden, that’s closer to truth?
Robert Lawrence Kuhn speaks with Sir Martin Rees, Steven Weinberg, Freeman Dyson, Peter Atkins, Lee Smolin, and Bas van Fraassen in “Where Do the Laws of Nature Come From?”—the 11th episode in the new season of the Closer To Truth: Cosmos, Consciousness, God TV series (50th in total).
The series airs on PBS World (often Thursdays, twice) and many other PBS and noncommercial stations. Every Thursday, participants will discuss the current episode.
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