Wayland's Principia

Alien: Unlike in appearance, history, and thought. Alien: Distant, too distant to reach, too far to travel in a universe bound by the speed of light. Alien: They did not come, but they sent word, words so strange that humans would have to devote their lives to mimicking alien appearance, taking in alien history, and following alien thought in order to understand them. No longer so human, generation by generation these Humans-Reaching-to-the-Alien become Guests on their own world. Until some of the aliens, on a ship in a long slow two-hundred-year arc from world to world, announce that they are coming to Earth to welcome their hosts and Guests. Hearing of this, one voice cries out a different word for Alien: Monster