Since the dawn of the space age, climbing toward the stars has required a breathtaking amount of rocket fuel, making trips into space both expensive and dangerous. 
Science fiction is the province of big dreams, and few dreams are bigger than our planet's very own stairway to heaven, the space elevator. This grand idea offers the promise of safe, inexpensive trips into orbit (and back!) on a daily basis. The space elevator was popularized by science fiction author Arthur C. Clarke in the novel Fountains of Paradise, and also plays a bit part in this month's book selection, Old Man's War.
The most surprising part of the idea: it's not as crazy as it sounds.
Jack and the GEO-Beanstalk
So how does it work? An anchor would be positioned in geostationary orbit, then connected to a base platform on Earth using a ribbon of ultra-strong carbon nanotubes. Mechanical lifters would climb up and down the ribbon, dropping the cost from today's $20,000 per kilogram to perhaps $100/kg. From How Stuff Works:
To better understand the concept of a space elevator, think of the game tetherball in which a rope is attached at one end to a pole and at the other to a ball. In this analogy, the rope is the carbon nanotubes composite ribbon, the pole is the Earth and the ball is the counterweight. Now, imagine the ball is placed in perpetual spin around the pole, so fast that it keeps the rope taut. This is the general idea of the space elevator. The counterweight spins around the Earth, keeping the cable straight and allowing the robotic lifters to ride up and down the ribbon.
Here's a short space elevator video (< 2 min.) to demonstrate the basic principles:
Why on Earth do we need one?
Construction of a space elevator would be a monumental undertaking, in terms of time as well as cost. So what benefits would we see from one? Here are some broad categories, from the frivolous to weighty:
- Entertainment & tourism. With multi-millionaires paying exorbitant fees to spend a few days on the cramped space station, space tourism is a no-brainer. There'd be incredible sightseeing, of course, but how about a null-gravity Olympics? Or a real-life version of the Battle Room from Ender's Game?
- Resource exploitation. Should it suddenly become trivial to move equipment and materials up and down the gravity well, then the near solar system (the Moon, asteroid belt, etc.) is suddenly ripe with possibilities. And how about a research station with 24 hour access to solar energy...
- Entrepreneurial innovation. Today's system of global commerce is largely the outgrowth of the trans-continental rail and highway systems. Who knows what might happen if we apply the free market engines of creation to the orbital plane? A space elevator could realign our relationship with outer space and transform the global economy.
- Exploration & colonization. During NASA's trips to the moon, the vast majority of the payload was spent on fuel for the outgoing and return journeys. It becomes far more economical to send probes to the moon, Mars, and beyond using the trip up the space elevator as a sort of slingshot.
Objects in future may be closer than they appear
When asked when he thought the vision might become a reality, Arthur C. Clarke responded "fifty years after everyone stops laughing."
Luckily for the rest of us, a devoted cadre of scientists and engineers has not only stopped laughing, but dedicated their lives to making the space elevator a reality. A Space Elevator Conference was recently held in in Redmond, WA; additional conferences are planned in Japan and Europe. There is also a space elevator reference site, a space elevator blog, and a space elevator foundation.
The Bremerton, WA Liftport Group is the most commercially ambitious of the lot, with a countdown clock on their Web site marking time until their tentative launch date of October 27, 2031. Their site also has a FAQ that includes a fascinating section on potential threats to the space elevator such as space debris, extreme weather, and terrorism.
Would you like to know more? NOVA recently produced an informative and inspiring special on the space elevator. The clip below is about ten minutes long, and includes footage from a recent X-Prize event in New Mexico:
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Other posts on Book Club for Old Man's War, by John Scalzi:
by Robert A. Heinlein - 
by Joe Haldeman - Gritty, action-packed, and outstanding novel. Haldeman also wrote a follow-up called 
that wasn't a direct continuation, but does deal with many of the issues raised in the first book.
by John Steakley - A "
: "War is the H-Word" was probably the single best episode of the show's glorious run, standing on equal ground with any "best of" Simpsons episodes, too. Sadly, there are no video clips available online, due to Fox's hyper-vigilant lawyers. We'll have to settle instead for a long list of 
by Cormac McCarthy. Posts about this book: