^I learned it in school, but completely forgot. Nikolaus Otto
   made the first one back in 1867, 144 years ago. Since we depend
   on it daily, it's good to be reminded how it works. Suck the
   fuel/air in, compress it (which heats it up), spark then BOOM,
   which pushes it back down, then the final stroke blows out the
   waste. Intake, Compress, Power, Exhaust. Repeat. Can't go to
   Walmart without it.^