Sunday, January 19, 2014

Sanity Checking

A persistent food myth is that "margarine is one molecule away from being plastic". You can use the method I recommended in an earlier blog post to fact check this one, but there's another way which is "sanity checking".

If I told you that putting three small pebbles in a line on the dashboard of your car would make your car go faster, you would think I was insane. You don't need to Google if it's really true, or look it up on Snopes or Google Scholar, because it fails the sanity check. You may not understand in perfect detail how an internal combustion engine works (I certainly don't), but you know enough to know that lining up pebbles on the dashboard is not going to influence the speed.

How does the "plastic margarine" claim do when subjected to the sanity check? It fails on two points.

  1. Margarine is made of a mixture of stuff, all mixed together (source: I looked at the ingredients on a tub of margarine). It isn't one single molecule to start with, so how can it be "one molecule away from being plastic"? That's like saying "chicken casserole is one molecule away from being plastic". It obviously can't be true.
  2. Unlike margarine, plastic isn't a mixture of things. If you have a plastic cup, for example, the plastic in that cup is made up of lots of molecules all alike. But there are lots of different kinds of plastic made of different kinds of molecules (source: the Wikipedia page about plastic). So the plastic in a plastic cup might be different from the plastic in a plastic bag or a plastic food container and so on. So it doesn't make any sense to say margarine is one molecule away from being plastic. Which plastic? Polystyrene? Nylon? PTFE? It's so vague it's nonsense.

You can use Wikipedia and Snopes and Google Scholar and Google to fact check the "plastic margarine" claim if you like. I strongly recommend you do - remember don't take my word for it, never take any single source of facts on faith. But I'll eat my own hat if you find that it's true. It's not a sane claim; it can easily be dismissed using basic sanity checking.


Seve Howe said...

What happens if something fails one person's sanity check and passes someone else's? Quantum Mechanics fails mine! :-)
I know at least one of is wrong, but the others?

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