Language & WorldMental model
The first law of geography fits in one sentence.
Waldo Tobler wrote in a 1970 paper on Detroit's growth: "Everything is related to everything else, but near things are more related than distant things." The sentence underpins spatial autocorrelation: neighbouring places have similar rents, similar weather, similar election results. Interpolation methods that turn a few measuring points into whole maps, like weather maps, rest on it.
Useful: Missing a value for one place, the nearest neighbour is usually a better estimate than the national average.
Source: en.wikipedia.org