Fun Science Fact #33: Common sense is common. That’s not a good thing.
I recently made the mistake of scrolling down into the comments section of an article I’d been reading. The topic was climate change—specifically, the role that improved fuel efficiency can play in slowing it down. In the article, the author noted that automotive emissions are particularly problematic because burning a single gallon of gasoline produces about twenty pounds of CO2.
As you can probably guess, the commenters jumped all over this. Clearly, here was evidence not only that global warming is a myth, but that the liberal stooges who believe in it are completely lacking in common sense. A gallon of gasoline, many commenters pointed out, weighs in at just a bit over six pounds. How can burning six pounds of fuel produce twenty pounds of waste? Ridiculous!
Well, this assertion is a bit counter-intuitive. It’s also 100% true. Gasoline is a hydrocarbon. It’s mostly made up of octanes, which are molecules containing eight carbon atoms and eighteen hydrogen atoms. When you burn gasoline, it reacts with oxygen in the air (this is why Elon Musk will be taking a Tesla with him to Mars) to produce two new types of molecule: carbon dioxide (CO2) and water (H2O). Note that each CO2 molecule contains only one atom taken from the gasoline. The other two come from the air. Note also that each oxygen atom is actually about a third heavier than each carbon atom. The result? Yeah, burning a gallon of gas produces twenty pounds of CO2, along with about nine pounds of water.
Okay, fine. Proving that internet trolls are dummies is like shooting fish in a barrel. However, common sense can be misleading to smart people too, often in subtle ways, and failing to recognize when you’re being misled can result in very bad outcomes. Here’s a favorite example of mine: some years ago, there was a push to require small children on airplanes to use car seats. Seems like common sense, right? I fly a lot, and I’ve experienced some pretty rough patches. I have a very vidid memory of my orange juice rising up out of my glass over Wisconsin once, hovering there in front of me for an instant, and then splattering all over my lap. I shudder to think what might have happened at that moment if I’d been holding a child, and hadn’t been paying full attention to her. Making parents buy seats for their kids might cost a bit of money, but surely it would save tiny, vulnerable lives.
Well, no. Fortunately, before legislation mandating child seats on airplanes made its way through the legislature, somebody actually thought to study what the net effects would be rather than just intuiting them. What they found is that if small children were required to purchase seats on commercial flights, the extra expense would prompt a certain number of parents to forgo flying, and drive where they needed to go instead.
This is where we remember that (again, counter-intuitively for many folks) flying is almost infinitely safer than driving. Because this regulation would force many parents onto the roads, the number of kids who would be saved from turbulence and rough landings would be vastly outweighed by the number who would die needlessly in auto accidents. Passing this common sense safety regulation would in fact cost lives, not save them.
The takeaway here is this: common sense is a fine and necessary thing. It allows us to make our way through the world without being paralyzed by the need to think through the ramifications of every tiny decision. However, in America in 2016, there is an unfortunate tendency to elevate common sense and intuition above actual knowledge. This tendency manifests itself in the increasing rejection of expertise in areas as diverse as climate science (Humans are changing the climate? Crazy!); economics (Free trade obviously hurts the American worker. Derp!); and even medicine (Who are you to tell me that my kid needs to be vaccinated?) Thinking for yourself is generally a good thing, but… this is a complex world, and there are people out there who spend their lives studying individual parts of it. Every once in a while, particularly on complicated topics, it might not hurt to listen to them.
