Robert Bryce is author of “Smaller Faster Lighter Denser Cheaper,” and many other books and articles about energy. Coal is denser, contains more energy, and is easier to handle than wood. Oil takes up half as much space as coal and can be transported easily and cheaply by pipeline. Natural gas can be used for many of the same purposes as oil, including terrestrial transportation, power generation, and space heating, but is now cheaper than oil (on a Btu basis). Gas emits about half as much carbon dioxide as coal and creates far fewer air pollutants than either oil or coal. Electricity (which of course must be manufactured from coal, natural gas, oil, uranium or thorium) is extremely flexible, is easily transported via wires, and can be switched on or off with the flick of a switch. Using carbon-based fuels like coal, oil, and natural gas to create cleaner, more ordered forms of energy like electricity provides opportunities to use evermore sophisticated tools, with computers and lasers being prime examples of this trend.