“How do you know the moon is not made of green cheese?”

Theoretical physicist Sean Carroll at the ScienceWriters2011 conference in Flagstaff on October 17th.

“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. How do you know it’s not made of green cheese?

“The answer is that it’s absurd to think the moon is made of green cheese.

“And the formalization of that absurdity is that we are allowed to use other things we know about the universe when judging the plausibility of a hypothesis…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….

“This is not a proof, there is no metaphysical proof, like you can proof a statement in logic or math that the moon is not made of green cheese. But science nevertheless passes judgments on claims based on how well they fit in with the rest of our theoretical understanding.”