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Long predicted but slow to arrive, robots may finally have their day. Within decades, says M.I.T. robot designer Rodney Brooks, the world could be filled with small, single-purpose, semi-intelligent creatures. He describes, for example, tiny insect-like vacuum cleaners that will hang out in dusty corners, scooping dirt into their bellies. When they hear the big vacuum robot coming, they will scurry to the center of the room, empty their innards and run back under the sofa.
Robots will eventually learn a human trait: reproduction. And the smart ones will be able to improve on the original pattern with each new copy. Self- replicating devices that are mobile, can find their own sources of energy and evolve from one generation to another could satisfy many of the criteria that have come to be associated with living things, says Steven Levy, author of a new book called Artificial Life. In the next century, says Levy, "we'll relate to our machines as we now relate to domestic animals."
The most important self-replicating machines, says Eric Drexler, will be microscopic atom-stacking factories, or "assemblers." Drexler, the author of Engines of Creation, believes that within the next few decades, armies of assemblers will be programmed to turn out a wide range of consumer goods, from featherweight spacecraft to paper-thin television screens. "Many of the things we can expect to see in the next 100 years will resemble the wild ideas of the 1950s and 1960s," he says.
TRANSPORTATION
The future's lightweight, superefficient cars will still be equipped with conventional steering and accelerators for knocking around the neighborhood and countryside. But highways will be embedded with electronics to monitor and control speed and traffic patterns, so that driving on the most heavily traveled freeways will become increasingly effortless. Commuters in the latter half of the century will simply get on the freeway, punch in their destination and let the electronic control systems take over. Collision-avoidance software could speed cars along at 200 km/h (120 m.p.h.) with no more than a few feet between each vehicle.
For medium-distance travel, new forms of mass transit are likely to dominate. Magnetically levitated locomotives will zip along at up to 500 km/h (300 m.p.h.). Lightweight materials will enable aircraft to carry as much as three times the passenger load of today's jumbo jets. For those who can afford the tickets, a few airlines might even offer services on a supersonic, suborbital Orient Express that would hop from Los Angeles to Tokyo in only two hours.
ENERGY
Fuel sources will probably change as dramatically in the coming century as they have in the current one. Scientists may find that the environmental effects of carbon dioxide and other greenhouse gas emissions are far worse than expected, which would prompt a virtual ban on the burning of hydrocarbons, says Livermore's Holzrichter. But what's next? Some experts believe so-called inherently safe reactors will have progressed so much by that time that the environmental movement will embrace nuclear fission. Others see a mix of solar, geothermal, tidal and wind power. By the end of the century, the big industrial nations may begin to rely on fusion, a safer form of nuclear energy that creates far less radioactive waste.