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See Inside January 2012

Physics Uncowed

You don't have to say cheese to get the picture



Matt Collins

Sean M. Carroll does not mince words. On October 17 he also did not cube them, dice them or thinly slice them, even when he was seriously discussing the theory that the moon is made of green cheese. Just to be clear, the discussion was serious, not the theory, when Carroll spoke at the ScienceWriters2011 conference in Flagstaff, Ariz.

A noted theoretical physicist, Carroll is not to be confused with noted evolutionary biologist Sean B. Carroll. The Sean Carroll duality may be one reason that the physicist version often muses about the multiverse.

“How do you know the moon is not made of green cheese?” asked Carroll, a senior research associate at the California Institute of Technology, author of the entropy examination From Eternity to Here and blogger for another publication you can sometimes Discover at magazine stands. “People will say, ‘Well, we’ve landed on the moon, we’ve picked it up, we’ve brought pieces of it back.’” Such people might think that as late as 1969 there was still widespread uncertainty about the moon’s curd content.

“But that’s just the surface,” Carroll Havartily argued. “Of course, there’s a layer of moon dust a few meters thick that sits on top of the green cheese. How do you know that most of the moon, 99 percent, is not really green cheese? And they will say, ‘Well, we know the mass of the moon, the density, and so forth.’ But don’t think that you fully understand the properties of lunar green cheese. This is very dense cheese.”

The physicist yet again posed his provolone problem: “How do you know it’s not made of green cheese?” He then cut the Goudaian knot. “The answer is that it’s absurd to think the moon is made of green cheese.” (If you were hoping for an explanatory equation, mull over the fact that a cylinder of mozzarella of radius z and height a has a volume equal to pi z z a.)

Carroll allowed his reasoning to ripen. “The formalization of that absurdity,” he said, “is that we are allowed to use other things we know about the universe when judging the plausibility of a hypothesis. The real reason the moon isn’t made of green cheese is not because we’ve gone there and brought pieces of it back. It’s because cheese comes out of cows, ultimately, or sheep or goats.”

Ah, but what about any influence from the cow that jumped over the moon? Frankly, I find the story of a cow that reaches escape velocity without the aid of a powerful multistage rocket far-fetched. And I think the absurdity argument can be applied here as well.

“Cheese,” Carroll continued, “was not part of the primordial solar system. We have a theoretical understanding of how the solar system works and how planets are formed that precludes the possibility that the moon is made of green cheese. Just like the reason why we know you can’t bend spoons with your mind is not because we’ve caught people on The Tonight Show faking it. It’s because it would violate the laws of physics. The moon being made of green cheese would violate how the solar system works.” I’ll go further than Carroll. I contend that the moon being made of cheese of any color is impermissible.

“That the moon is not made of green cheese,” Carroll said of his Gorgonzolic gripe, “is not a proof, the way you can prove a statement in logic or math. But science nevertheless passes judgments on claims based on how well they fit in with the rest of our theoretical understanding.”

Despite the existence of well-established and powerful theoretical frameworks, some individuals may still hold an Edelpilz epistemological notion that only the samples brought back by astronauts were truly decisive. Or even that a deep moon core sample is still necessary to settle the lunar Limburger. But such people have truly lost their whey.

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