In Patterns, Not Particles, Physicists Trust
The late physicist Frank Oppenheimer used to get furious when people told him he should act in a certain (usually conventional) way because, they argued, this was the “real world”; one had to adjust. He responded: “It’s not the real world. It’s a world we made up.”
While Oppenheimer was usually referring to social expectations or the administration of the science museum he founded, he was also speaking as a true physicist.
After all, telling the difference between the “real world” and the “world we made up” is a major preoccupation for physicists. Are the 11 dimensions of time and space proposed by “string” theory real? What about exotic, as yet undiscovered, particles of “dark matter”? What about the repulsive energy of empty space?
One needn’t get so exotic. Consider this newspaper. Is it real? Certainly, it’s made of chemical compounds, which are made of molecules, which in turn are made of atoms. Are atoms real? If you stood inside one, you’d see enormous amounts of empty space, with little fluffs of electric charge buzzing around the far periphery; in the center, a tiny nucleus composed of protons and neutrons.
Are protons real? Anything as small as a proton behaves more like a wave than a particle. Not a wave of matter, mind you, or even a wave of energy, but a “probability wave.” This probability wave tells you the likelihood of finding the proton in a given place.
Under close enough scrutiny, the real world of matter as we know it evaporates. We’re left with patterns, relationships--in particular, symmetrical relationships that look the same no matter how you turn them. “In the physicist’s recipe for the world, the list of ingredients no longer includes particles,” notes Nobel laureate Steven Weinberg of the University of Texas. “Matter thus loses its central role in physics: All that is left are principles of symmetry.”
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Einstein proposed that we believe things are “real” only insofar as we relate to them through our senses of sight, hearing, touch and instruments that are extensions of our senses. “The concept of the ‘real external world’ of everyday thinking rests exclusively on sense impressions,” he wrote.
But sense impressions are processed in the mind--itself a slippery concept.
“So what is this mind, what are these atoms with consciousness?” asked the late Caltech physicist Richard Feynman. “Last week’s potatoes! That is how we can remember what was going on in my mind a year ago--a mind which has long ago been replaced.”
Feynman points out that no single atom in the brain is a permanent resident. “The atoms come into my brain, dance a dance, then go out: always new atoms but always doing the same dance, remembering what the dance was yesterday.”
If pinning down reality is a matter of seeing consistent patterns, then humans are well equipped, because ferreting out patterns is what we do best: We see patterns in the stars, on the moon, in the cracks in the ceiling, in the orbits of the planets.
Arranging things into patterns makes them easier to understand. But only sometimes do the patterns point out “real” relationships.
The orbits of the planets are connected by a single law of gravity, but the stars in the Big Dipper are connected only by our imagination. Both are real, but the motions of the planets tell us things about nature; the dipper in the sky tells us only about ourselves. All too often, we mistake the “real world” for one that exists mainly in the human brain.
“Having lost the gods, we fall in love with the beautiful idols we can raise in their places,” writes Amherst College physicist Arthur Zajonc in his book, “Catching the Light.” “Atoms, quarks, tiny black holes . . . they are reified, garlanded, and dragged forward to assume a place in the temple. Calling them real, we animate them. . . .”
In the end, finding out what’s real may require redefining what we mean by reality. After all, science often requires that we go beyond sense impressions (as well as common sense). No matter how real or unreal something might seem, it ultimately has to stand up to experimental scrutiny and theoretical consistency.
The chair is real because you can sit on it. Newton’s laws of gravity are real because they keep the planets in orbit around the sun. Real enough to command our attention, in any event. Real enough so that they can’t be easily ignored. Or as Weinberg puts it: “When we say that a thing is real, we are simply expressing a sort of respect.”
