Previous books on space have discussed extensively how man will get to the moon and the planets and what it will probably be like on those terrains. The book briefly resurveys the how and what and adds a new dimension for younger readers-- the why. Scientists can now make fairly confident guesses about the natural resources in space and from this knowledge can predict the vast effects on the economy and way of life on earth. They even foresee the possibility of changing the atmosphere and weather of now uninhabitable planets so that men may colonize them. In an informed and pleasantly conversational style, the author conveys not only the concrete facts and the educated guesses, but also a feeling for the dreadful loneliness and unimaginable change that space explorers may expect to experience. For readers too young for Ordway's Conquering the Sun's Empire, the book has large, easy print.