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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.

與太空旅行相比，時(shí)間旅行很顯然是一個(gè)更為復(fù)雜的命題。簡(jiǎn)而言之，愛(ài)因斯坦的觀點(diǎn)就是，宇宙中每一物體都有其自身的“時(shí)間”，并隨其運(yùn)動(dòng)的不同而不同。物體運(yùn)動(dòng)越快，其時(shí)間越慢(與運(yùn)動(dòng)較慢的物體相比而言)。最極端的假設(shè)是，如果一個(gè)物體運(yùn)動(dòng)達(dá)到光速，那么其時(shí)間就會(huì)完全停止。但無(wú)論一個(gè)物體或者一個(gè)人的時(shí)間為何，它只能參照其它物體才能得以體現(xiàn)。換句話說(shuō)，萬(wàn)物皆相對(duì)。

Many science-fictional ideas from the past have subsequently became scientific realities. Take space exploration, for example. In the 1950s this was just a fantastical idea that few people would have dreamt could actually happen. Now it's such a part of modern life that the latest blastoff of a spacecraft, or the discovery of a new planet often doesn't even make the national news.

以前科學(xué)小說(shuō)中提出的很多想法已經(jīng)變成了科學(xué)的現(xiàn)實(shí)。拿太空探險(xiǎn)來(lái)說(shuō)，50年代，這只不過(guò)是一種科學(xué)狂想，很少人相信有一天會(huì)變成現(xiàn)實(shí)?？墒乾F(xiàn)在它已成為現(xiàn)代生活的一個(gè)組成部分，以至于一次最新的宇航器發(fā)射或者一個(gè)新行星的發(fā)現(xiàn)已不再列為國(guó)內(nèi)新聞。

Relevant link：

2012公共英語(yǔ)二級(jí)考試每日一練（8月20日）

（責(zé)任編輯：中大編輯）

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