科学家们认为土卫二冰火山的活跃时间只占其寿命时间的1%到20%，幸运的是，卡西尼号飞越土卫二的时候正好赶上了喷发期。

Scientists believe the cryovolcanism on Enceladus has only been active during 1 to 20 percent of its existence. We’re glad Cassini caught it in an eruptive phase.

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各种干预措施，如抗感染药物，可以增加人口的平均存活时间，但只有那些减缓人体衰老速度的方法才能延长最长寿命。

Various interventions, such as infection-fighting drugs, can increase a population's average survival time, but only approaches that slow the body's rate of aging will increase the maximum lifespan.

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然而，这种比较忽略了其他相关因素：闲暇时间、预期寿命和经济不平等。

However, that comparison omits other relevant factors: leisure time, life expectancy, and economic inequality.

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What I plot on this graph here is as a function time, years, dates, life expectancy as a function of time.

在这儿的这张图是,一个关于时间,年,日期的函数,将寿命长短作为时间的函数

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