The economic destiny and prosperity of entire nations may rest on one question: Can silicon-based computer technology sustain Moore's law beyond 2020? Moore's law (see sidebar) is the engine pulling a trillion-dollar industry. It's the reason kids assume that it's their birthright to get a video-game system each Christmas that's almost twice as powerful as the one they got last Christmas. It's the reason you can receive (and later throw away) a musical birthday card that contains more processing power than the combined computers of the Allied Forces in World War II.
The secret behind Moore's law is that chipmakers double every 18 months or so the number of transistors that can be crammed onto a silicon wafer the size of a fingernail. They do this by etching microscopic grooves onto crystalline silicon with beams of ultraviolet radiation. A typical wire in a Pentium chip is now 1/500 the width of a human hair; the insulating layer is only 25 atoms thick.
But the laws of physics suggest that this doubling cannot be sustained forever. Eventually transistors will become so tiny that their silicon components will approach the size of molecules. At these incredibly tiny distances, the bizarre rules of quantum mechanics take over, permitting electrons to jump from one place to another without passing through the space between. Like water from a leaky fire hose, electrons will spurt across atom-size wires and insulators, causing fatal short circuits.
Of course, cyber Cassandras have been tolling the bell for Moore's law for decades. As physicist Carver Mead puts it, "The Chicken Little sky-is-falling articles are a recurring theme." But even Mead admits that by 2014 the laws of physics may have their final revenge. Transistor components are fast approaching the dreaded point-one limit--when the width of transistor components reaches .1 microns and their insulating layers are only a few atoms thick. Last year Intel engineer Paul Packan publicly sounded the alarm in Science magazine, warning that Moore's law could collapse. He wrote, "There are currently no known solutions to these problems."
The key word is known. The search for a successor to silicon has become a kind of crusade; it is the Holy Grail of computation. Among physicists, the race to create the Silicon Valley for the next century has already begun. Some of the theoretical options being explored:
--THE OPTICAL COMPUTER This computer replaces electricity with laser light beams. Unlike wires, light beams can pass through one another, making possible three-dimensional microprocessors. An optical transistor has already been invented; unfortunately, the components are still rather large and clumsy. The optical counterpart of a desktop computer would be the size of a car.
--THE DNA COMPUTER One of the most ingenious ideas being pursued is to compute using DNA, treating the double-stranded molecule as a kind of biological computer tape (except that instead of encoding 0s and 1s in binary, it uses the four nucleic acids, represented by A, T, C, G). This approach holds much promise for crunching big numbers. Hence large banks and institutions may one day use it. However, a DNA computer is an unwieldy contraption, consisting of a jungle of tubes of organic liquid, and is unlikely to replace a laptop in the near future.