The author believes it is humanity’s destiny to inhabit other planets in our solar system and beyond. When you finish Entering Space, you may be convinced as well. In The Case for Mars (1996), Zubrin outlined an ambitious plan that would allow astronauts to live on Mars for extended periods of time. Entering Space broadly covers this and a number of other topics, from the recent discovery of planets in other solar systems to commercial applications of space travel. The author argues that we are currently a Type I civilization, having mastered our own planet. A Type II civilization, he states, will have conquered the solar system, and a Type III will have moved out into the galaxy. Some of the possibilities presented are fascinating, including power satellites that could generate or relay electrical power to remote areas of the world and solar sails that would use the radiative force of the sun or an earth-bound laser (the “photoelectric effect,” for those readers sporting pocket protectors) to passively sail around the solar system. Throughout the book, Zubrin is undaunted by technological hurdles and funding obstacles to the projects he envisions. He argues that NASA and the aeronautics industry are preventing commercial development (by start-up companies, including his own) of inexpensive rocket technologies to launch satellites into orbit. His plans include a passenger rocket-plane that would travel briefly into space, happily giving the passengers the chance to —experience zero gravity and perhaps enjoy the novelty of a brief float around the cabin.” (More likely, they would have the opportunity to revisit their in-flight meal.) Other ambitious forecasts include a matter/antimatter engine, which would require thousands of times more energy than is currently produced on Earth in an entire year. An irrepressibly optimistic view—more persuasive than one might expect—of the future of space travel and colonization, both within the solar system and beyond.