Gradually you accelerate upward, reaching a cruising speed of several hundred miles per hour. Your elevator car moves up a cable 100 million times as long as it is wide—connected on one end to a platform in the ocean and, on the other end, to a counterweight, a heavy mass orbiting high above the planet—kept taut by centrifugal forces. It takes about two weeks to reach the top of the cable, some 60,000 miles above the Earth’s surface. But the trip is serene, with none of the G-force of a rocket ride.
Are space elevators the...