A recent visit to Venice, Italy got me thinking about the model train set I had as a kid, and how it taught me the meaning of scale. For those who have never played with model trains, they come in two different scale sizes: N and HO. HO is the larger of the two, with a ratio of 1:87.1, while N gauge ranges from 1:148 to 1:160. Because of this difference in scale, an HO caboose seriously dwarfs an N caboose when sitting side by side. Serious model train aficionados (i.e. adults) would never dream of mixing HO with N.…