Try the following thought experiment. Go to the center of a city and find a comfortable place to sit. Look around and ask yourself: Where and how is energy being used? What forms of energy are being consumed, and what work is that energy doing? Notice the details of buildings, cars, buses, streetlights, and so on; notice also the activities of the people around you. What kinds of occupations do these people have, and how do they use energy in their work? Try to follow some of the strands of the web of relationships between energy, jobs, water, food, heating, construction, goods distribution, transportation, and maintenance that together keep the city thriving.

After you have spent at least 20 minutes appreciating energy’s role in the life of this city, imagine what the scene you are viewing would look like if there were 10 percent less energy available. What substitutions would be necessary? What choices would people make? What work would not get done? Now imagine the scene with 25 percent less energy available; with 50 percent less; with 75 percent less.

Assuming that the peak in global oil production occurs in the period from 2006 to 2015 and that there is an average two percent decline in energy available to industrial societies each year afterward, in your imagination you will have taken a trip into the future, to perhaps the year 2050.

But how can we be sure that oil will become less abundant? Petroleum geologists like Colin Campbell (formerly with Texaco and Amoco) point to simple facts like these: Oil discovery in the U.S. peaked in the 1930s; oil production peaked roughly forty years later. Since 1970, the U.S. has had to import more oil nearly every year in order to make up for its shortfall from domestic production. The oil business started in America in the late nineteenth century, and the U.S. is the most-explored region on the planet: more oil wells have been drilled in the lower-48 U.S. than in all other countries combined. Thus, America’s experience with oil will eventually be repeated elsewhere.