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These varied sources would produce electricity for local consumption and clean-burning hydrogen for distribution via pipelines. According to one estimate, a single solar-cell farm covering roughly one-quarter the area of New Mexico could supply enough electrically produced hydrogen to replace all the fossil fuels consumed in the U.S. If the necessary real estate can't be found on the planet's surface, the solar collectors could be parked in orbit, beaming energy to earth via high-power microwaves.
WARFARE
The weapons of the future will look like they came straight out of Star Wars or RoboCop: everything from hand-held laser swords to autonomous robots programmed to kill. The long-term trend, as demonstrated in the Persian Gulf last year, is toward short battles conducted at long distance by increasingly intelligent machines. Defense experts predict that the next arms race will be to develop the smartest, stealthiest and most accurate weapons and to demonstrate their superiority convincingly enough in advance to avoid risking lives and expensive hardware on the battlefield.
The biggest problem will be proliferation, not only of nuclear fuel and arms but also of poison gases, biological toxins and other awful things no one has yet dreamed up. If tin-pot dictators and drug cartels get hold of the technology, they will become increasingly troublesome. Even a cheap, radio- controlled model airplane can do a lot of damage if, say, it is carrying a genetically engineered anthrax spore.
As a rule of thumb, says Bell Labs' Penzias, technology will provide for people of the future what only the wealthiest can buy today. Where the rich now hire chauffeurs to drive them to work, for example, the working stiff of the future will be transported to work in his robocar. None of these advances are without their costs and risks. Drexler's assemblers, for example, could create bounties of goods and services -- or they could unleash artificial pests of unimaginable destructiveness. One nightmare creature from Drexler's book: an omnivorous bacteria-size robot that spreads like blowing pollen, replicates swiftly and reduces the biosphere to dust in a matter of days.
None of this, of course, is etched in stone -- or in silicon. In the end, what propels science and technology forward is not just what can be done but also what society chooses to do. As the brief history of the nuclear age has taught, powerful technologies are hard to rein in once they've been loosed on the world. Is humankind mature enough to handle the possibilities of intelligent robots, self-replicating machines and virtual sex? Fantastic new opportunities are sure to come. The hard part will be deciding which ones to pursue and which to bypass.