BOB GARFIELD: If you were paying close attention to the previous interview, you might have noticed that I invoked the Heisenberg Uncertainty Principle to get at the idea that journalists, as observers, will necessarily affect the outcome of whatever it is they observe. If you weren't paying close attention, here's a reminder. [MOMENT FROM EARLIER IN THE SHOW PLAYS]

BOB GARFIELD: Now, there's something called the Heisenberg Uncertainty Principle, which in physics says that it's very difficult to track a subatomic particle, because any means you use to track it actually changes the path of that particle, and in journalism we call it the Observer's Paradox, that the very process of reporting on a story can change the outcome of that story. Okay, now the producers of this show have very quickly pointed out to me that my cultural fluency about science is, you know, a little lacking. A quick Nexis search shows that I'm not the only one in the media who would benefit from a conversation with John Rennie. Rennie is the editor in chief of Scientific American, and he joins me now to set me straight on the Heisenberg Uncertainty Principle and other scientific principles. John, welcome back to OTM.

JOHN RENNIE: Oh, it's my pleasure. Thanks to be here, Bob.

BOB GARFIELD: All right. Now, I felt pretty confident invoking Heisenberg to make that analogy. But I didn't get it quite right, did I?

JOHN RENNIE: Ah, well, you see Bob, you're right. In physics, there are always concerns about how, when you make an observation, you might be perturbing the system, but that's not what the Heisenberg Uncertainty Principle is. The Heisenberg Uncertainty Principle actually talks about something that's kind of more devious about the way the universe is set up. It says that certain properties of things have a kind of reciprocal relationship, in such a way that the more precisely you know the value of one of these traits, the other trait becomes less precise. So, for example, the more precisely you know the position of a bullet at any one moment, the less precisely you know what its velocity is. Here's one way you could try to understand that. You can take a photograph of the bullet as it whizzes by, and you look at the picture, and you get a little bit of blurring in that picture of the, of the image. From that blurring, you can calculate, maybe with a great deal of certainty, exactly what the velocity of the bullet is. But unfortunately, because of that blurring, you now don't know what the exact position of that bullet was. If you use a shorter shutter speed, you can get to the point where you know the precise position of the bullet, but now the bullet looks completely motionless in your picture, and you have no idea of what its velocity was any more.

BOB GARFIELD: Okay. Mea culpa. What analogy might I have used from science to communicate the idea of this Observer's Paradox?

JOHN RENNIE: Well, the, the Observer's Paradox is a little bit closer to something called Schrodinger's Cat. This comes from a kind of whimsical thought problem that was proposed a long time ago in which suppose that you had a mechanism set up that will release a small amount of poison gas and that is controlled by some kind of radioactive device. You know over a certain amount of time that it will definitely decay and it will set off the poison gas, but you don't know exactly when that will happen. Now, you put this in a box with a cat, and you can't look inside the box, and the question is, at any given moment is the cat alive or is it dead? Our usual intuition of these things says the cat must surely be either alive or dead at any one time, but that's not necessarily what physics says has happened. According to physics, when you open that box and look at it, you're collapsing the possibilities, and that's the moment the cat becomes truly either alive or dead. That's more like the Observer's Paradox you were talking about.

BOB GARFIELD: John, I'm just wondering. You know, Feb-yoo-ary - pronounced without the first R has been mispronounced so often that it's now in the dictionary under the incorrect pronunciation, as are a number of other words. Is it possible that people like me have been so abusing the Heisenberg Uncertainty Principle that it has somehow evolved into a useful term anyway, because when we use it, people fully understand the point we're trying to make?

JOHN RENNIE: And I suppose we could fill a whole liberry with ideas and words [LAUGHTER] that people are misusing. But I think still it's worthwhile for people like me to come out here and, and try to at least set people straight on what some of these scientific ideas mean, partly because it helps people understand the science that much better, but also because sometimes people are missing the opportunity for some other perfectly good metaphor. Why misuse one when maybe there's a, some other circumstance out there that's just begging to have the Heisenberg Uncertainty Principle used right?

BOB GARFIELD: Well, John, as always, thanks very much.

JOHN RENNIE: Oh, it's my pleasure. Thank you, Bob.

BOB GARFIELD: John Rennie is editor in chief of Scientific American. [MUSIC]