by Rob Welham
BEIJING, May 5 (Xinhuanet) -- Professor Stephen Hawking has suggested humans might one day be able to construct spaceships capable of such speeds that time on board would slow down. Such a craft could travel thousands of years into the future, reaching distant star systems within the lifetime of its crew.
“Time travel was once considered scientific heresy and I used to avoid talking about it for fear of being labelled a crank, but these days I’m not so cautious,” Hawking says in his ongoing series being broadcast on the Discovery channel.
He suggests humanity could build a giant “relativistic” spaceship, so called because it would exploit the science set out by Albert Einstein in his theories of relativity.
Einstein found that as objects accelerate through space, the rate at which time passes for them slows down. For objects such as cars and aircraft the effect is negligible, but Hawking’s spaceship would exceed 98 percent of the speed of light, when such effects would be extremely powerful.
Hawking said such a ship could theoretically reach speeds of more than 1,000 million km/h, but would have to be built on a huge scale simply to carry all the necessary fuel.
“It would take six years at full power just to reach these speeds. After the first two years it would reach half light speed and be far outside the solar system. After another two years it would be travelling at 90 percent of the speed of light,” he said.
