There's just one little problem to consider before you rush to book your ticket. Gliese 581c is 20 light years away - over a million times the distance from Earth to the sun. The journey there would make NASA's best efforts to explore our own solar system seem like a trip to the shops, and to get there in a human lifetime a craft would need to travel awfully fast. Even at half the speed of light you'd spend the best part of 50 years cooped up in a smelly space capsule. So what are the options?

There is no question that conventional chemical rockets aren't up to the task. The fastest interstellar craft to date, Voyager 1, is now heading out of the solar system at about 17 kilometres per second. At this rate it would take 350,000 years before what's left of your bones reaches Gliese 581c. Making maximum use of gravitational fields to accelerate your starship before it leaves the solar system - swinging close by the sun, say, so its intense gravity acts like a slingshot - isn't likely to make a significant difference. Nuclear-powered rockets that harness the heat from fission reactions to create an exhaust of high-velocity particles would cut nine-tenths off the journey time, but tickets for the 30,000-year trip are unlikely to find many takers.

Another possibility is to cruise through space on a sailing ship: make a reflective sail, unfurl it in space, and it will get nudged along by photons streaming out from the sun. This creates a slow but steady acceleration that can eventually add up to some serious travelling. According to engineers at US space research company Pioneer Astronautics, it's possible to make a solar sail that could propel a craft to around 1 per cent of the speed of light. The key, they suggest, is to use a mesh of metal-coated carbon nanotubes. The ultra-lightweight sail this creates, just nanometres thick, could pass close to the sun after launch without melting. The intense illumination, as well as extra acceleration from the sun's gravity, could boost the sail to speeds of over 3000 kilometres per second. Now you would reach Gliese 581c in around 2000 years.

Source - NewScientist 

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