While we're very far from a future where starships will be the norm, this hasn't stopped scientists, engineers and science-fiction writers at the Royal Astronomical Society (RAS) in London to discuss the latest ideas about how interstellar travel might be made to work in the real world.
The chief problem, as Adams noted, is distance. During the cold war America spent several years and much treasure (peaking in 1966 at 4.4% of government spending) to send two dozen astronauts to the Moon and back. But on astronomical scales, a trip to the Moon is nothing. If Earthwhich is 12,742km, or 7,918 miles, acrosswere shrunk to the size of a sand grain and placed on the desk of The Economists science correspondent, the Moon would be a smaller sand grain about 3cm away. The sun would be a larger ball nearly 12 metres down the hall. And Alpha Centauri B would be around 3,200km distant, somewhere near Volgograd, in Russia.
Chemical rockets simply cannot generate enough energy to cross such distances in any sort of useful time. Voyager 1, a space probe launched in 1977 to study the outer solar system, has travelled farther from Earth than any other object ever built. A combination of chemical rocketry and gravitational kicks from the solar systems planets have boosted its velocity to 17km a second. At that speed, it would (were it pointing in the right direction) take more than 75,000 years to reach Alpha Centauri.
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