Our planet is constantly monitored by hundreds of space-borne instruments. This book describes the technology of those instruments and the sciences that provide useful information from them. It also discusses the political implications of space-borne monitoring. From the moment satellites were launched into orbit their ability to see what was happening on a global scale was appreciated - and feared. This well researched book strives to answer such diverse questions as: Are satellites really a threat to individual privacy? How bad, really, is climate change and global warming? Why can't we find Osama bin Laden? Does the world have enough fresh water? The military side of the story is linked to the big security issues that we face, such as terrorism and civil wars. The civilian side of the story involves numerous successful collaborations in weather forecasting, navigation, communications, and other such 'peaceful' uses of satellite surveillance. How the world handles the knowledge gained from these Earth watchers will be critical in the years to come, and Norris skillfully leads us through the issues and possible paths we can take.