When the Science Fiction Museum and Hall of Fame opened in Seattle, the skateboard from the movie Back to the Future and the teleporting platform from Star Trek were part of the exhibits. But Dr. Donna Shirley, the museum's founding director, believes the most likely concept to become science nonfiction is a space elevator that goes up and down thousands of miles and that can act as a giant slingshot to propel spacecraft far and out. She should know - she used to manage the Mars Exploration Program at the Jet Propulsion Laboratory. Although she relied on rockets to get her probes to Mars, she thinks it's important to break away from total rocket dependency.

Sir Arthur C. Clarke, who put space elevators in his 1978 book The Fountains of Paradise, is another enthusiast who thinks reality could catch up with fantasy. The 1990 discovery of very strong carbon molecules called nanotubes makes the idea even more likely, because their extraordinary strength could help designers overcome previous engineering obstacles.

In October 2005, Spaceward Foundation, which was cofounded by Ben Shelef, helped stage the first Space Elevator Games. They were held to spur inventiveness and to push some buttons to get space elevators moving in the public consciousness in the same way the X-Prize competition triggered private efforts for space travel. NASA's relatively new Centennial Challenge program, designed to accelerate and direct needed innovation, offered cash prizes for the first time ever.

The concept is this: A counterweight in space is connected to an anchor point on Earth via a thin, ribbonlike tether. The rotation of the earth throws the counterweight outward, keeping the ribbon taut. The ribbon is three to five feet wide, thinner than paper, and 62,000 miles long. Robotic cars ride up the ribbon, powered by a light beam that illuminates photovoltaic cells on their underside. Supporters say if it works, cargo and passengers could go up and down 62,000 miles. That's the equivalent of about 33 million stories.