Illuminating the Future of Energy A few centuries ago, the developing world got most of its energy from windmills, from water mills, from whales and from plants. Plants contributed both wood for making heat and biofuels to power the labor of humans and other animals. Nowadays, the "developed" world gets most of its energy from fossil fuels -- coal, oil and natural gas -- along with nuclear power and hydroelectric dams. But this era of easily accessible fossil fuels is likely to be but a brief blip in the history of humanity. The peaks of oil and gas production are expected to be reached within the next 50 years, and coal production is likely to peak about the end of this century, if business continues as usual. Moreover, scientists advise us that we would be wise to leave a lot of the fossils in the ground, to reduce the risk of climate change. So where will the world get its energy from next -- when, inevitably, humans stop using fossil fuels? Is it realistic to imagine a comfortable return to renewable energy sources? Whales are not a realistic source of oil anymore, but could windmills, water mills, energy crops and all the other renewable options provide enough energy for today's vastly increased population to maintain today's lifestyle? Discussion of those questions is astonishingly polarized. On the one side, advocates point out that the earth receives more energy from the sun in just one hour than the world's population uses in