This book describes how America will deal with the coming decline in fossil carbon energy and the "replacement energy" sources we will need to exploit on an unprecedented scale by 2100.  Half the book explores the physics background we need to understand our use of energy. The remaining half deals with the coming drastic decline in available fossil carbon energy and how we can cope with this decline. The huge scale the replacement energy we will need is not appreciated now, but will become apparent once the most critical U.S. energy source-oil-starts to decrease in availability around the end of this decade.