This third edition tells readers why astronauts are weightless, why satellites don't fall from the sky, how we will live on Mars, and whether or not there is life elsewhere in the universe. This book has been updated with recent information on the science and technology involved in the new frontier of space. It is written as a textbook for an undergraduate liberal arts course, with or without mathematics. Subjects covered include: orbital decay; concepts for removing debris from LEO; LEO vs GEO for communications satellites; cell phones via satellite; radar satellites; Hubble space telescope servicing missions; orbiter modifications; new observations of the sun; GPS applications; videoconferencing; and magnetic levitation.