Satellite technology, for its part, was just starting to affect everyday life at the time of Apollo 8. The Intelsat consortium, led by U.S. company Comsat, operated communications satellites that handled a growing share of international phone traffic. "If you wanted to make a telephone call from New York to London, you probably went on the satellite," Whalen says. "There were still some issues with delay and echo, but there were still more links by satellite" than through terrestrial lines.

Satellites were not yet widely used in television broadcasting, due to the higher bandwidth and costs involved, and most people still received only a handful of channels. "The ability to start binding the world together—it hadn't quite happened by December 1968 because we didn't have enough satellites up there," Whalen says. "But people already saw that within a few years there would be no place on Earth that you couldn't get a satellite connection to any other place on Earth."

The Apollo missions helped spur the growth of satellite communications, as NASA signed on as a major customer of the Intelsat system. The communications network supporting Apollo 8 included Intelsat satellites, one of which was an Intelsat 3 that was launched days before the mission and which performed among its first tasks the transmission of the astronauts' Christmas Eve greeting from lunar orbit to Europe.

Four decades later, there has been a role reversal of sorts. Satellite communications, along with orbiting weather and GPS systems, are so widespread now that consumers largely take them for granted, whereas human spaceflight, limited to low Earth orbit, rarely gets a degree of attention even close to that on the night before Christmas 1968.