2013年6月英语四级听力SectionC外刊原文_大学英语听力

2013年6月英语四级听力SectionC外刊原文

　　Scientists have demonstrated that an ordinary airplane flight is like a brief visit to the Fountain of youth. In 1972, for example, scientists who took four atomic clocks on an airplane trip around the world discovered that the moving clocks moved slightly slower than atomic clocks which had remained on the ground. If you fly around the world, preferably going eastward to gain the advantage of the added motion of the Earths rotation, the atomic clocks show that youll be younger by only 40 billionths of a second. Even such an infinitesimal saving of time proves that time can be stretched. Moreover, atomic clocks have demonstrated that the stretching of time increases with speed.

　　Here is an examples of what you can expect if tomorrows space-flight technology enables you to move at ultrahigh speeds. Imagine youre an astronaut with a twin who stays home. If you travel back and forth to the nearest star at about half the speed of light, youll be gone for 18 Earth years. When you return, your twin will be 18 years older, but youll have aged only 16 years. Your body will be two years younger than your twins because time aboard the flying spaceship will have moved more slowly than time on Earth. You will have aged normally, but you have been in a slower time zone. If your spaceship moves at about 90% of lightspeed, youll age only 50% as much as your twin. If you whiz along at 99.86% of lightspeed, youll age only five percent as much. These examples of time-stretching, of course, cannot be tested with any existing spacecraft. They are based on mathematical projections of relativity science.