Time travel is clearly a trickier proposition than space travel, though. Put simply, Einstein s idea was that every object in the universe has it s own “time”, and these vary as objects move. The faster an object moves, the slower its time is, compared to the time of a slower moving object. The extreme situation would be if an object could move as fast as the speed of light, its time would be completely halted. But whatever an object--or person s--time is, it s only evident in contrast to other objects. In other words, it s all relatives. 与太空旅行相比,时间旅行很显然是一个更为复杂的命题。简而言之,爱因斯坦的观点就是,宇宙中每一物体都有其自身的“时间”,并随其运动的不同而不同。物体运动越快,其时间越慢(与运动较慢的物体相比而言)。最极端的假设是,如果一个物体运动达到光速,那么其时间就会完全停止。但无论一个物体或者一个人的时间为何,它只能参照其它物体才能得以体现。换句话说,万物皆相对。 编辑推荐:名师指导公共英语阅读考试技巧 公共英语pets三级全真模拟试卷 公共英语pets二级语法讲解汇总