Well, since there's going to be a lot of flippant remarks here, I'm just gonna say language. It's how we communicate thought and intellect.
For a more flippant remark...well...little background. I'm in Central Vermont, which was hit hard by Hurricane Irene. My house (Well, the house of the mother of an old friend who I'm renting from) had 3 feet of water in the first floor, and ive been without utilities of any sort since the end of August (At night, ive spent days either at work or at a friends). Based on this, I can say that hot water is the single most amazing invention ever. Seriously. Hot water is more amazing then space travel.