The satellite photo was very clear. It looked like it had been taken from only a few thousand feet in altitude. Pavlos easily recognized the elevation contour markings that lay upon apparently typical Grecian highlands. He had, after all, been teaching map reading and leading expeditions while his young American friend had been scrawling stick figures in crayon on the kitchen wall in his parents’ house in Des Moines.

The photos lay on his dining room table, three stories above the noisy streets of Athens. Outside his apartment door children ran down the hall, screaming in some incoherent game. To him it was all part of the background. He worried over the other lines and squiggles on Frank’s map, reluctant to admit his ignorance to the astronaut, however close they had become during a mission in the Sudan, two years before.

“This is in Thessaly, is it not?” He pointed to the shape of the hillsides, the lay of the sun in the creek beds, wishing to show that expertise meant as much as did fancy technology.

Frank’s eyebrows rose. Impressed, he showed it with typical American ingenuousness. Americans had no second skin, no Mediterranean wall of caution. Pavlos loved them for it.

“Yes, that’s right,” Frank had said. “And here you see how the population density and terrain accessibility profiles rise and fall together nicely everywhere.

He pulled out another photo.

“Here is the city of Thessalonica, with almost a million people. Now weighted only against local resources, there’s no good explanation for its population advantage over, say, Larisa a bit farther south. But taking into account factors such as travel times along various egress points, terrain…