Paper and Insulation, the Clueless Version

Thermal conductivity

We like a good joke from time to time, and one of our favorites is the one about mankind's greatest invention. One person answered "the wheel," one answered "fire," and the dummy answered "a thermos bottle." When asked why the thermos bottle, the dummy answered, "It keeps hot things hot. It keeps cold things cold. How does it know?" Well, it's for sure that our old friend Lexa W. Lee couldn't help answer that question, as she proved in her post to Leaf.tv, "What Makes Paper a Good Cup Insulator?"¹

We've seen Lee's work before, and this one's in keeping with her typical pattern; citing what she considered an authoritative reference in her very first sentence:

"Paper makes a good cup insulator because it is able to reduce the conduction, convection and radiation of heat, according to the Illinois Physics Van of the University of Illinois."

We aren't real sure why the U of I calls it "the van" (or even if they call it "the van,"), but either way, Lexa made a critical mistake: the website wasn't answering the same question. Instead, some grad student was explaining the three processes ("conduction, convection and radiation") someone else had already mentioned. Since Lee was apparently unfamiliar with the term "thermal conductivity," she looked no further – but she should have.

No, all Lexa did was reword parts of Tom's answer to Sinead, and she botched even that. For instance, she claimed that

"The wood fibers in the paper trap air and prevent convection, which refers to air moving through and carrying heat with it..." ...which is a better answer for expanded polystyrene (styrofoam) cups than paper, though let's be real: no cup allows convection through its walls, because otherwise it would leak! Lexa also blathered on about heat radiation, which she says paper cups don't do because they're opaque to light; though she didn't say whether clear glass transmits more heat than translucent or opaque...

No, Lexa, no matter what some grad student said (and we hope he got a D in that course!), the reason paper cups make good insulators is because they're anisotropic and made of fibers that have a low thermal conductivity. Thermal conductivity is a function of the atomic or molecular structure of the substance. Lexa couldn't be bothered to look that up, however, and that's why we're awarding her yet another Dumbass of the Day; her fourth...

¹ Strangely, the Leaf.tv entry seems unchanged except that the company took Lee's name off the byline when they moved it from eHow...

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