We must look back into history to understand our energy problem. Twice in the last several hundred years, there has been a transition in the way people use energy. The first was about 200 years ago, when we changed away from wood--which had provided about 90 percent of all fuel--to coal, which was much more efficient. This change became the basis of the Industrial Revolution. The second change took place in this century, with the growing use of oil and natural gas. They were more convenient and cheaper than coal, and the supply seemed to be almost without limit. They made possible the age of automobile and airplane travel. Nearly everyone who is alive today grew up during this period, and we have never known anything different. Because we are now running out of gas and oil, we must prepare quickly for a third change--to strict conservation and to the renewed use of coal and to permanent renewable energy sources like solar power.

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "We must look back into history to understand our energy problem. Twice in the last several hundred years, there has been a transition in the way people use energy. The first was about 200 years ago, when we changed away from wood--which had provided about 90 percent of all fuel--to coal, which was much more efficient. This change became the basis of the Industrial Revolution. The second change took place in this century, with the growing use of oil and natural gas. They were more convenient and cheaper than coal, and the supply seemed to be almost without limit. They made possible the age of automobile and airplane travel. Nearly everyone who is alive today grew up during this period, and we have never known anything different. Because we are now running out of gas and oil, we must prepare quickly for a third change--to strict conservation and to the renewed use of coal and to permanent renewable energy sources like solar power." in the context of "" to mean that wisdom is timeless.