DEAR READER, THIS IS THAT BOOK.

AFTERWORD

It seems that scientists are often attracted to beautiful theories in the way that insects are attracted to flowers—not by logical deduction, but by something like a sense of smell.

—STEVEN WEINBERG

In January 1999, Poul Anderson sent me a letter enclosing his essay on his invented flying aliens, the Ythrians, which he had used in his novel The People of the Wind. I had liked the novel and so had asked him as part of a proposed anthology for details on the planet and its aliens. My notion was a collection of stories dealing with aliens in scrupulous detail, with attention paid to how they evolved, how that affected their worldview, and how humans might react to them. Maybe there would be humans in the stories, maybe not.

The anthology idea didn’t fly, alas—editors are creatures easily made cautious. Plus, they get fired. Meanwhile, Poul was a meticulous writer, working out an integrated vision for a novel, though few of these work-out manuscripts apparently saw print. He was ready to write another story in one of his worlds, and it was a singular treat seeing how he had designed it.

To shape his idea, and confer with me by phone about it, he sent me his thirteen-page Ythri description, with solar system and planetary parameters in detail: “A G5 star, has only 72 percent the luminosity of Sol and less ultraviolet light in proportion; but Avalon, orbiting at a mean distance of 0.81 Astronomical Unit in a period of 0.724 Terran, gets 10 percent more total irradiation than man evolved under.”

His essay also included several of his sketches of these aliens and their anatomy, even diagrams of their wing bones and skull. He named the planet Ythri, which I’ve used in this book for its natives. It’s a world with 0.75 Earth’s gravity and a denser atmosphere, both physical elements explaining how smart flying aliens could evolve. His body plans and physiology proceed from solid constraints, including their body mass (about 30 kg, 66 English pounds) and detailed molecular chemistry. There are words for local plants and crops and domesticated animals, too. I’ve kept his details, with some small alterations to fit my story.

From a parallel short story, “Wings of Victory,” I’ve taken some Ythri culture, speech, and attitudes, and even phrases Poul made up in their language. Poul worked out and wrote up in great detail far more than he used, a signature of the Hal Clement school of planet-building, as admirably shown in Clement’s founding novel of the school, Heavy Planet. It’s like Hemingway’s dictum: know more than will be on the page; if you do that, the reader feels it. It wafts through the prose.

Further, I wrote from the viewpoint of a character and situation I’ve been developing in a story series about what a SETI Library might look like when we have a host of messages to work through, and exoplanet data as well. Most SF is about discovery of a signal, as in Jim Gunn’s The Listeners, the first to do so, a remarkable novel. Few have thought about an era when we will have many Messages (to use the capitals conferring importance, in that future Library) to make a Librarian’s job far more dense and thrilling. Since librarians have an image as calm, scholarly introverts, why not have one who is the opposite? Though she doesn’t at first know this…