With advances toward ultrastrong fibers, the concept of building an elevator 60,000 miles high to carry cargo into space is moving from the realm of science fiction to the fringes of reality.
This month, the Los Alamos National Laboratory was a sponsor of a conference to ponder the concept. Yet, the keynote address was by a titan of science fiction, Arthur C. Clarke, speaking via satellite from his home in Sri Lanka. ''I'm happy that people are taking it more and more seriously,'' said Mr. Clarke, whose novel ''The Fountains of Paradise'' (1978) revolved around such a space elevator.
The discovery in 1991 of nanotubes, cylindrical molecules of carbon with many times the strength of steel, turned the idea from a fantastical impossibility to an intriguing possibility that could be realized in as little as a decade or two.
Proponents say the economic and technological advantages of a space elevator over rockets make it inevitable. They predict it will lower the cost of putting a satellite into space from $10,000 a pound to $100.
''As soon as we can build it, we should build it,'' said Dr. Bryan E. Laubscher, a scientist at Los Alamos who organized the conference. Just as the transcontinental railroad opened the West in the late 1800's, ''I feel the space elevator is going to be such a paradigm shift in space access,'' Dr. Laubscher said.
Easier economical access to space might also make practical other grandiose projects like solar power satellites that could collect sunlight and beam energy down to Earth.
The conference, a three-day session here, drew 60 people, a mix of scientists and engineers who are working on the concept, space enthusiasts who wanted to hear more and dilettantes from nearby Los Alamos laboratory attracted by curiosity.
''The first thought is, Is this really going to work?'' said Dr. Steven E. Patamia, a researcher at Los Alamos, who was enlisted into performing space elevator calculations a week before the conference. ''When you get into it, it begins to make sense. There are a good number of technical issues. They are probably all 'overcomeable.' ''
The original idea of a space elevator is more than a century old. In 1895, Konstantin E. Tsiolkovsky, a Russian visionary who devised workable ideas for rocket propulsion and space travel decades before others, proposed a tower thousands of miles high attached to a ''celestial castle'' in orbit around Earth, with the centrifugal force of the orbiting castle holding up the tower. (Imagine swinging a rope with a rock tied to the end of it.)
But the idea was fundamentally impossible to build. Steel, then the strongest material known, was too heavy and not strong enough to support that weight.
Other scientists periodically revisited and reinvented Tsiolkovsky's idea, inspiring science fiction writers like Mr. Clarke.
Nanotubes spurred NASA to take a more serious look in 1999. A team of scientists envisioned huge cables of nanotubes and magnetically levitated cars traveling up and down. The structure would be so large that it would require grabbing an asteroid and dragging it into Earth orbit to act as the counterweight for holding up the elevator.
To avoid weather, especially lightning, the NASA scientists envisioned the base station as a tower at least 10 miles high.
''We came out of that workshop saying the space elevator is 50 years away,'' said David V. Smitherman of the Marshall Space Flight Center, who led the study.
Around that time, Dr. Bradley C. Edwards, who was then a scientist at Los Alamos, read an even more pessimistic assessment, that a space elevator would not be built for at least 300 years.
''But there was no information why it couldn't be built,'' Dr. Edwards said, and he took that as a challenge.