A space elevator is a structure that would be used to cheaply transport cargo and people from
the Earth's surface into space. Many different designs have been proposed. The most common plans
involve a paper-thin ribbon, a meter wide, made of carbon nanotubes. This ribbon is anchored to
an offshore platform on the equator and reaches to a counterweight 100 000 km straight
up. As the Earth rotates, the inertia of the tether works against gravity and keeps it up.
Electrically powered climbers would move up and down the space elevator at 200 kph.
To better understand this, think of spinning a ball on a string around your hand. The
ball doesn't just flop down, it actually opposes the force of gravity and stands outward. In
this analogy, your hand is the Earth, the ball is the counterweight and the string is
the space elevator tether. This is how a space elevator would work. The counterweight spins around the
Earth, keeping the cable straight.
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