Reductio ad Meteorite

Reductio ad absurdum is a Latin phrase meaning "to reduce to absurdity".  It's a debate technique where you take your opponent's line of reasoning and point out that it leads to conclusions that are absurd - and therefore the line of reasoning must have some unseen flaw.

I recently witnessed an argument about whether or not it was safe to use a cell phone while pumping gas.  In theory, electricity can ignite gasoline vapors.  The consequences are highly undesirable, so you should avoid any risk, right?  But think about it - every time you get out of your car in the wintertime, you get a SNAP of static electricity.  It's caused by the dry wind against the car's shell, and the arc can be well over 1000 volts.  If that open discharge doesn't ignite the lingering vapors at a gas station, what will?  And what's the voltage inside a sealed cell phone anyway, three volts?  Nine?

Whenever I consider odds like this, I say you're as likely to be hit by a meteorite.  If risk is what you're talking about, then the stress of worrying is far riskier than what you're worrying about.  Reductio ad meteorite.  (By the way, this concept isn't limited to risk, but all the most common examples - say, fear of flying - are about risk.  Why?  Because people are lousy at evaluating and comparing small risks.)


  1. BTW, and FWIW the dielectric strength of dry air is 33,000V/cm. Any spark long enough to see is likely to be well over ten thousand volts.

  2. Myth Busters did an episode on this. The statistics state no examples of cell phone + gas pump = explosion, but there are some examples of people (mostly women) who start pumping gas but get in and out of their car repeatedly, thereby generating static and then causing an explosion/fire. Evidently men are more likely to stand at the pump but women are more likely to get back into the vehicle and then get back out when ready.

  3. At first I was surprised Mythbusters would have looked into it - but then I remembered the "blow stuff up" aspect of the situation. heh.

    I wanted to include some links about the psychology of risk; I could swear Ars Technica had run a really compelling article about it, but I couldn't find it. I'll tack on a comment later if I come across it.

  4. For years I have stopped the microwave prior to the beep going off. Robert has never understood this and thought I was the only one. Turns out, according to him, there's an entire group on FB for this activity. However, I think for some of these people it is a risk-aversion thing (the microwave may explode), or an OCD thing (must stop before the bell or the planes will fall). For me it's a sound thing (I don't like loud sudden noises).