November 29, 2010
(Re)name that Metaphor (correctly this time)
I’ve never been in this position, but the person demanding a newspaper or magazine correction—the insider claiming he was quoted out of context; the scientist whose nuanced position didn’t come across, quite; the dead person who’s not really dead—must get a certain satisfaction from seeing the correction printed. It might be the grim satisfaction of a wrong set to rights too late, but satisfaction nonetheless. Then again, in a digital publication, a correction can work to the source’s advantage in some sense. If s/he finds the mistake early enough, an editor can amend it instantly and make sure that (most) everyone reads the correct sentence the first time. Some publications even mark the factual boner with an asterisk, which not only emphasizes the correct version of things, but provides some instant sympathy for the wronged party.
But as a disinterested reader, I’d never gotten actual delight from a correction until a few weeks ago, when the New York Times ran one for an article about study skills and retention (“Forget What You Know About Good Study Habits”). I’d read the uncorrected article online at first, then went back to reread it, for reasons soon ejected from my mind. I’d gotten through half the story, and was going to click through to the second page. And I was grimacing in anticipation of a paragraph I knew was coming up. The author had needed a metaphor conveying something about unintended consequences, and apparently wanted the imprimatur of science. So he fell back on that canned summary of the Heisenberg Uncertainty Principle—you know, the idea that measuring a property of a particle alters the property itself.
Except that’s not what the Uncertainty Principle says. All the Principle actually says, in its entirety, is:
∆x∆p ≥ h/4π
Now if you insist on translating quantum mechanics into English (always risky), the Principle says the uncertainty in a particle’s position (∆x) multiplied by the uncertainty in its speed and direction (taken into account through its momentum, ∆p) always exceeds the number “h divided by four times π.” (The h stands for Planck’s constant, a very tiny number; the π is the familiar constant from circles, 3.14159...) In simpler terms, if you know a particle’s position very well, you cannot know its momentum well at all, and vice versa.
The reason you can’t know both the exact position and exact momentum of a particle at once is that, down on the submicroscopic level, which is the only level where the Uncertainty Principle really applies, particles behave as much (or more) like waves than discrete particles. And unlike with a particle, it’s nigh impossible to draw neat boundaries around a wave and say exactly where it is and what direction it seems to be going. In other words, the titular uncertainty isn’t uncertainty about measuring anything, as if you had a poor ruler; it’s uncertainty built into nature, intrinsic to the wave-like character of reality on such tiny scales.
Now it’s also true of course that measuring something does sometimes change what’s being measured. That happens on a macro level—checking the air pressure on your tires will change the pressure of the air inside them, since you let a little of that pressurized air out—and it happens on a micro level—since subatomic particles are so small that probing them even with light will bump them around. But that insight has nothing to do with uncertainty. Because even if you discovered a perfect measuring tool that didn’t bump them around, you cannot measure the position and momentum accurately at the same time on a very small scale.
The idea that measuring something changes what’s being measured already has a name, actually, albeit an insipid one—it’s the Observer Effect. In fact, beyond just being banal, the name seems to downgrade its importance. When very young, most of us probably observed, informally, with our fellow humans, that observing someone changes the way s/he acts. Indeed, there’s a deep psychological truth there. And as soon as you assimilate it and realize how far its implications reach, and that certain forms of psychological objectivity go right out the window as a result—this also seems intrinsic to the way the world works, and it needs a name. It’s something that we want to express with a law or a principle, not a mere effect. So no wonder that people rejected “Observer Effect” and poached on prestigious and oracular quantum mechanics instead: How much more learned!
It’s basically a branding problem: The Observer Effect needs a snappier name (feel free to start suggesting some below). But the first step in changing the name will be letting people know the problem, and why the name needs changing. Which is why the correction in the New York Times delighted me so much. “An article on Tuesday...” it said, “described incorrectly the Heisenberg uncertainty principle in physics. The principle holds that the act of measuring one property of a particle (position, for example) reduces the accuracy with which you can know another property (momentum, for example) — not that the act of measuring a property of the particle alters that property.”
I have no idea who insisted upon the correction here. Perhaps a physicist who roused himself from the usual indifference with which most physicists accept the mangling of this metaphor in everyday parlance. Perhaps a philosopher who also knows what “begging the question” really means and wasn’t about to let this injustice slide either. Perhaps a copy editor somewhere still fighting the good fight, still insisting that we can rescue “disinterested” and eradicate “irregardless,” too. But, regardless, it’s the most satisfying correction I’ve ever seen in a publication—and gives me hope that we can salvage the proper meaning of the Uncertainty Principle, and still honor the need for a (more cleverly named) Observer Effect. Indeed, while people usually refer to the Observer Effect as something unfortunate—because it doesn’t allow you to make an objective measurement—this may be one case where observing someone’s behavior changes it for the better.
Posted by Sam Kean at 01:00 AM | Permalink