COAL, CRUDE OIL, and natural gas, which are known as fossil fuels, were originally discovered thousands of years ago. But only in the past several hundred years has their use become widespread. When humans first learned that they could extract the fuels from the earth and burn them, the world began to change. Since that time, industry has grown, technology has flourished, nations have become wealthier, and people now enjoy a lifestyle their ancestors could never have dreamed of—and all these advances have been possible because of fossil fuels.

Today, these fuels are used all over the world. For instance, most of the world's electric power plants burn coal to heat water in huge boilers. When the water becomes hot enough to change into steam, it turns large turbines that create electricity. Coal provides power for about 40 percent of the...