We've grown accustomed to thinking of space travel as something that requires big, powerful rockets and complex spacecraft capable of re-entry and landing, an approach that costs an awful lot of money for each launch and requires a daunting amount of technical precision to pull off. Wouldn't it be easier if we could just get on an elevator and ride it slowly but steadily into orbital space, as if we're going for lunch to some restaurant on the top floor of a skyscraper?
Such a magical apparatus also would enable us to return to Earth just as easily, without having to experience the rigors and risks of rapid reentry through the Earth's atmosphere. Sounds a bit kooky, doesn't it? In fact, however, scientists have been envisioning a space elevator since Russian physicist Konstantin Tsiolkovsky, who was inspired by the Eiffel Tower, first proposed it back in 1895. Over the decades, a number of visionaries -- from the Russian astronaut Yuri Artsutanov to science fiction author Arthur C. Clarke -- have seconded the notion.
For a long time, the concept seemed hopelessly impractical because, according to Newtonian laws of motion, the tension on such a lengthy cable would be greater than the tensile strength of steel, causing it to snap. But with the advent of super-strong carbon nanotubes, 180 times tougher than steel, visionaries again are talking about the idea of building such an elevator, for which a cable would be threaded though the core of a geosynchronous satellite and attached to a counterweight approximately 62,000 miles above the Earth. One limitation, at least at this point, is that scientists have only been able to create a few centimeters of pure carbon nanotube, and they probably would need a vastly longer strand to make the elevator work. Even so, futurist Michio Kaku envisions that such an elevator might be built between 2070 and 2100 [source: Kaku].