If the young Sun was much fainter and cooler than the Sun today, liquid water couldn't have existed on either planet.

如果早期的太阳比现在的太阳暗淡，也没有现在这么炙热的话，那么液态水就不可能在这两个星球上存在。

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Hess suggested that the presence of water, probably released from minerals decomposing in the Earth's mantle, might have meant that a high-magnesium magma could have existed at a lower temperature.

赫斯认为，水的存在可能是由地幔中分解的矿物质释放出来的，这可能意味着含镁高的岩浆可能在较低的温度下存在。

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An obsession with time, saving, gaming, wasting, losing and mastering it, seems to have been a part of humanity for as long as humans have existed.

人类对时间的执念——对其的节省、玩弄、浪费、丧失及掌控——似乎是人性的一部分，人类存在了多久，执念就存在了多久。

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This raises the exciting possibility that life may have existed in the past on Mars.

VOA: special.2009.12.30

Agricultural villages will have existed all over the place in the late Stone Age, in the Neolithic Period, as it is known. But there is a difference and the critical difference is that a city contains a number of people who do not provide for their own support.

农业村庄在石器时代后期,以及新石器时代随处可见,但二者是有区别的,最重要的区别在于,城市能容纳,相当数量,无需自给自足的人口

耶鲁公开课 - 古希腊历史简介课程节选

Because they would have started with the hypothesis, not that there existed a month, but that June was particularly likely.

因为他们是有了假设然后再开始做实验的，而不是说有一个这样特殊的月份，而是六月是一个特殊的月份。

麻省理工公开课 - 计算机科学及编程导论课程节选

Pay outlets have existed for years, like the Smarte Carte kiosks found at many airports.

FORBES: Prepare To Pay For Power In Public Places

Although impostors have existed for ages, the growing frequency and cost of identity theft is worrisome.

ECONOMIST: Identity theft

And I don't know if Dylan would have existed without coming out of that time.

NPR: Film Provides Kaleidoscopic Portrait of Bob Dylan