I’ll admit that I’ve got a bit of an obsession with man-made projects that are created on a scale which has to take into account things we’d never, ever need to worry about on a daily basis. For example, I’ve been fascinated by the Verrazano-Narrows Bridge ever since I learned that its builders had to take into account the curvature of the earth when they built it; as a result, the tops of the bridge’s two towers are nearly two inches further apart than the bases. (Could you imagine if every homebuilder and roadworker had to worry about the curvature of the earth in their projects?) It’s because of this obsession that I’m amazed I never knew that GPS has to take into account the theory of relativity in about a half-dozen different ways in order to function correctly — and if the engineers who designed it had failed to account for both general and special relativity, the locations given by our GPS receivers would be off by dozens of miles, and would get worse every day. That’s just damn cool.