Inventing Reality: Physics as Language by Bruce Gregory (John Wiley & Sons: $18.95; 230 pages)
Common sense tells us that there is a real world out there whose existence is completely independent of us. It existed before we were here, it continues to exist when we’re not looking at it, and it will be there after we depart this veil of tears.
We take this picture so much for granted that we hardly ever question it. Does anyone doubt that the newspaper you are reading is really there?
In this view, the job of scientists is to figure out the laws by which nature works. And of all the sciences, physics deals most with an independent world, a world of things, falling bodies, masses, atoms and the like.
Well, 20th-Century physics has tossed that picture into a cocked hat. Quantum mechanics, an immensely successful set of equations about the nature of matter, has unsettling implications, among which is that the world does not exist unless someone is observing it.
It’s best not to think about that. As Richard Feynman warned, “Do not keep saying to yourself, if you can avoid it, ‘But how can it be like that?’ because you will ‘get down the drain,’ into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.”
The only way to think about quantum mechanics is that the equations work. And leave it at that. What they say about the real world, the model they imply, who knows?
Bruce Gregory, associate director of the Harvard-Smithsonian Center for Astrophysics, says this state of affairs is nothing new. In “Inventing Reality: Physics as Language,” he argues that quantum mechanics simply brings into focus what has always been true. All that physicists have ever done, he says, is to invent mathematical models that work, more or less. We can never know whether they accurately portray reality--whatever reality is.
“A physicist is no more engaged in painting a ‘realistic’ picture of the world than a ‘realistic’ painter is,” he writes near the beginning of this book. Later he adds, “Physical theories do not tell physicists how the world is; they tell physicists what they can predict reliably about the behavior of the world.” Still later he says, “For better or worse, there is little evidence that we have any idea of what reality looks like from some absolute point of view. We only know what the world looks like from our point of view.”
The argument, of course, is as old as Plato. The people in the cave didn’t see the world. They saw its shadows, from which they inferred the world.
That, Gregory says, is the position that physicists are in. They -- we -- see the shadows, and the best they can hope to do is to come up with good formulas that accurately predict where the shadows will be next. Our ability to know the world is necessarily limited by what we see, by the categories we impose on what we see and by the language -- mathematics -- with which we talk about it.
“We have always dreamed of being able to talk about the world in the right way -- to talk about the world in what the American philosopher Richard Rorty calls ‘nature’s own language,’ ” Gregory says. “The history of physics makes it hard to sustain the idea that we are getting closer to speaking ‘nature’s own language.’ ”
Gregory’s book offers a reasonably good discussion of the history of physics. He argues that at every stage, regardless of what they thought they were doing, people were merely making up models rather than describing the world.
The history of physics has become a crowded field in recent years, and this book is as serviceable as most of the others. But it’s a familiar story.
Experience Says Otherwise
As for the argument: It is accurate, but its conclusions are unsatisfying. Maybe we’re deluding ourselves, but we certainly think there’s more to physics than a handy scheme for predicting the outcome of experiments. To say that physicists invent the world rather than discover it is to ignore every moment of our experience. It’s too weak.
Physicists may indeed throw up their hands at the implications of quantum mechanics, and they may indeed pay lip service to Gregory’s conclusion that we can’t know what the world is really like, but they don’t believe it. Deep down, physicists believe that what they are doing is describing reality, not just figuring out useful formulas.
No one knows why the world corresponds to their laws. No one knows why mathematics is so successful. No one knows why the universe is comprehensible at all. And it is unlikely that anyone will ever know the answers to these deep questions. It is unlikely that this debate will ever end.
We are not merely passive observers of an external world, though we usually function as if we were. Neither do we have infinite freedom to shape reality as we wish. The truth is somewhere in between. We can never be sure exactly where.