Rock Doc

We've all seen globes in classrooms. They represent the Earth well -- better than flat maps can do. But all the globes I've seen in schools have national boundaries on them, usually indicated by having nations in different colors. The U.S. is yellow, Canada is light green, Mexico is pink, and so on. When I was a child my big brother owned a globe like that, and I got to pore over it sometimes.

My sister-in-law has a different globe, one specially purchased for her by her father. It has no national boundaries -- so all of North America is presented as a unit, as indeed is each of the land masse...