For astronauts orbiting the Earth for 800 days, it starts to add up. 如果宇航员们环绕地球800天，其影响就会明显。

　　But what affects humans also affects machines. 言而，影响人类的也会影响机器。

　　Satellites of the global positioning system are also hurdling around the Earth at thousands of miles an hour. GPS的卫星同时也环绕着地球行驶，且速度为每小时数千英里。

　　So, time dilation kicks in here, too. 因此，时间在这情況也显见膨胀的。

　　In fact, their speed causes the atomic clocks on board to disagree with clocks on the ground by seven millionths of a second daily. 事实上，GPS卫星的行驶速度导致飞行着的原子钟与地上的原子钟之间产生每天7百万分之一秒之差。

　　Left uncorrected, this would cause GPS to lose accuracy by a few kilometers each day. 如果再不做校对的话，这将会令GPS失去准确性且产生每天几公里差异。

　　So, what does all this have to do with time travel to the far, distant future? 那么，这些和穿越时空和去遥远的未来有什么关系呢？

　　Well, the faster you go, the greater the effect of time dilation. 当行驶的速度越快，时间膨胀的效应越大。

　　If you could travel really close to the speed of light, say 99.9999%,  如果你行驶的速度真的能够接近光速的话，比方说，百分之99.9999，

　　on a round-trip through space for what seemed to you like ten years,  绕太空来回一圈，对你来说可能像过了10年，

　　you'd actually return to Earth around the year 9000. 但是当你回到地球时，将会是9000那年左右。

　　Who knows what you'd see when you returned? !  到那时候谁知道你回来后会看到什么？

　　Humanity merged with machines, extinct due to climate change or asteroid impact, or inhabiting a permanent colony on Mars. 人类与机器分不开，源于全球暖化或行星之间撞击的灭绝，又或是人类在火星定居了。

　　But the trouble is, getting heavy things like people, not to mention space ships, 但问题是，要把像人一样那么重的东西，莫说太空飞船了，

　　up to such speeds requires unimaginable amounts of energy. 移动到达接近光速般，是需要不能想象的巨大能量。

　　It already takes enormous particle accelerators like the Large Hadron Collider to accelerate tiny subatomic particles to close to light speed. 大量的粒子加速器如大型粒子对撞机被需要来把微小的亚原子粒子加速以接近光速。

　　But one day, if we can develop the tools to accelerate ourselves to similar speeds,  但是终有一天，如果我们能够发明一些工具可以让我们加速到如光速度般，

　　then we may regularly send time travelers into the future, bringing with them tales of a long, forgotten past. 到那时候，我们可能随时可以把穿越时空者送到遥远的未来，还有带着我们古老，被遗忘的故事去。