Gas Pump Wonders

The other day, as I was at a gas station, I got to wondering...how exactly does the gas pump know when the tank is full? I mean, if you think about it, it's kinda weird. You just stick the nozzle into the gas tank hole, press on the trigger and out comes the gas. It keeps going and going until finally it stops. But how does it know when it's time to stop so that your gas tank won't overflow? At first I thought maybe it was some kind of high tech wireless signal. Maybe the pump communicates with the car and they tell each other how much gas needs to be put in. Or perhaps when the end of the nozzle touches the inside of the gas tank, some kind of sensors communicate to the pump how much gas is needed. I honestly had no idea. lol So I looked it up online. Turns out it's actually quite simpler than I thought, yet still pretty clever. Apparently, at the end of the nozzle there is a small hole that sucks in air (like a vacuum). As the gas is pumping, it keeps sucking in the air. Once the gasoline inside the tank reaches the end of the nozzle, that little hole is blocked and starts to suck in some of the gasoline. That then is the signal that the tank is full and it triggers the "Off" switch. I never would've guessed. :)

Now, if we can only figure out some clever yet simple way to lower those damn gas prices! lol