Density and Pressure for Dummies (Metric System 7)

Density on display

Our staff here at the Antisocial Network long ago realized that, among many others, one of the reasons why Google invented their Panda update (well, actually, Mr. Panda invented Google's update) is that the overall "truthiness" of the internet had greatly suffered from the rubbish published at content farms. Bad actors could, without consequences, vomit out any kind of bull on these sites, and often make substantial money by doing so. One such site, often the target of our wrath, was eHow.com; a site that became the poster child for bushwa because they'd let anyone publish almost anything about any topic. Take, for instance, the rubbish their "contributor" Charlotte Johnson had to say about "How to Convert Grams Per Meter Squared to Pounds Per Square Foot" (now "niche-ing" at Sciencing.com).

There are a bazillion different conversion sites on the internet that will do just that for you automagically (three cheers for elementary javascript programming classes). There are also many that will provide the necessary conversion factor so you can see it for yourself. But we're pretty certain that only one person has ever said the following:

"Grams per square meter and pounds per square foot are both measurements of density"

As we're wont to say around the Antisocial Network office, "Is this woman nuts, stupid, or both?" We mean, did she really say those are units of density? Density, which is mass per unit volume, while square feet are a measure of area? We suspect Johnson was confused by the wikipedia entry that says they're units of areal density, which is used only by a few specific industries, in particular textiles and paper-making – you'll note that both industries' products are too thin to measure with a ruler... Once she's gotten that bit of stupidity out of the way, Charlotte then goes inform her readers that this conversion is a three-step process. According to Ms. Johnson (a teacher! small wonder our education system is in shambles!), the steps are

1. Convert the mass from grams to pounds: multiply by 0.0022 : close enough for government work...
2. Convert the area from m² to ft²: multiply by 10.76 : ditto
3. Divide the number of pounds by the number of ft²

Well, that oughta work. But we find the process rather clumsy and potentially error-prone; although we know exactly why Charlotte stretched it out so much: eHow Demands a minimum of three steps in their "how-tos." No, if we were teachers we might explain the derivation of the conversion factor, but we'd simply tell our students to divide g/m² by 4891. It's a darned sight simpler.

Charlotte got confused about the definition of "density" – badly confused, we might add – and then turned a simple process into something complicated through overtelling. With those three math operations instead of one, Johnson's readers are three times as likely to make an error during the conversion. And that's the kind of information that earns people our Dumbass of the Day award.

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MM - METRIC SYSTEM