Wilcox sees three main challenges facing humanity over the next century: the need to exercise restraint in the use of energy or end up with a ""global heat disaster""; the necessity of avoiding large-scale use of nuclear energy or facing a ""certainly intolerable sequence of radioactive threats to our whole physical and spiritual environment""; and the imperative to produce sufficient food. His packaged panacea is a combination of solar energy and farming seaweed in the ocean. Rather than face a power shortage, he says, we might soon confront a surfeit of power that could produce enough heat to melt the polar ice caps and flood large areas of land. His evidence is not impressive. As Wilcox admits, long-range climate trends are still not very well understood and some specialists think, on the contrary, that the earth is undergoing a cooling trend. Wilcox does not discuss the possibilities of advancement in the technology of nuclear power safeguards or the move toward greatly increased efficiency. He doesn't even deal with the practical and technical problems of perfecting solar energy use on a large scale. In a few pages at the end he makes some thought.provoking comments about the systematic cultivation of seaweed for food and industrial raw materials: a pilot project is underway off California. One man's pet theory, not very scientifically pursued.