The Encyclopedia of Astrobiology, Astronomy, and Spaceflight - The Encyclopedia is an on-line A-Z maintained by astronomer/author David Darling and is part of The Worlds of David Darling website Some of the content is based on his books, including The Universal Book of Astronomy, The Complete Book of Spaceflight, The Extraterrestrial Encyclopedia, and Life Everywhere: The Maverick Science of Astrobiology. Other entries are unique to the on-line Encyclopedia and have, in some cases, been suggested or provided by outside parties. The goal is to provide a comprehensive source of information covering contemporary astronomy, astrobiology, and astrophysics, SETI, space missions, advanced propulsion concepts, historical aspects, and biographies (past and present). It is intended to be of use to the interested layperson, student, and academic alike. Every effort is made to keep the Encyclopedia accurate and up to date. This has been added to Astronomy Resources Subject Tracer™ Information Blog.