The process of ageing
原文
Lesson 37
The process of ageing
What is one of the most unpleasant discoveries we make about ourselves as we get older?
At the age of twelve years, the human body is at its most vigorous.
It has yet to reach its full size and strength, and its owner his or her full intelligence: but at this age the likelihood of death is least.
Earlier, we were infants and young children, and consequently more vulnerable;
later, we shall undergo a progressive loss of our vigour and resistance which, though imperceptible at first
will finally become so steep that we can live no longer,
however well we look after ourselves, and however well society, and our doctors, look after us.
This decline in vigour with the passing of time is called ageing.
It is one of the most unpleasant discoveries which we all make that we must decline in this way, that if we escape wars,
accidents and diseases we shall eventually 'die of old age', and that this happens at a rate which differs little from person to person,
so that there are heavy odds in favour of our dying between the ages of 65 and 80.
Some of us will die sooner, a few will live longer -- on into a ninth or tenth decade.
But the chances are against it,
and there is a virtual limit on how long we can hope to remain alive, however lucky and robust we are.
Normal people tend to forget this process unless and until they are reminded of it.
We are so familiar with the fact that man ages, that people have for years assumed that the process of losing vigour with time,
of becoming more likely to die the older we get, was something self-evident
like the cooling of a hot kettle or the wearing-out of a pair of shoes.
They have also assumed that all animals,
and probably other organisms such as trees, or even the universe itself, must in the nature of things 'wear out'.
Most animals we commonly observe do in fact age as we do,
if given the chance to live long enough;
and mechanical systems like a wound watch, or the sun,
do in fact run out of energy in accordance with the second law of thermodynamics (whether the whole universe does so is a moot point at present).
But these are not analogous to what happens when man ages.
A run-down watch is still a watch and can be rewound.
An old watch, by contrast, becomes so worn and unreliable that it eventually is not worth mending.
But a watch could never repair itself--it does not consist of living parts, only of metal, which wears away by friction.
We could, at one time, repair ourselves--well enough, at least, to overcome all but the most instantly fatal illnesses and accidents.
Between twelve and eighty years we gradually lose this power;
an illness which at 12 would knock us over, at 80 can knock us out, and into our grave.
If we could stay as vigorous as we are at twelve,
it would take about 700 years for half of us to die, and another 700 for the survivors to be reduced by half again.
译文
第37课
衰老的过程
随着年龄的增长，关于我们自己，我们会发现哪些最令人不快的真相（或事实）呢？
在十二岁的时候，人体正处于最旺盛的发育阶段。
它还没有达到自己的最大体型和最强壮的状态，其主人也尚未发挥出全部智力；不过在这个阶段，死亡的风险是最小的。
早些时候，我们还是婴儿和幼儿，因此更加脆弱。
后来，我们的体力和抵抗力会逐渐减弱；虽然这种变化起初并不明显，但最终会变得显而易见。
最终，情况会变得如此糟糕（或：形势会变得如此严峻），以至于我们再也无法生存下去了。
无论我们自己多么注重保养身体，无论社会和医生为我们提供了多么优质的医疗服务，情况依然可能不尽如人意。
这种随着时间推移而逐渐减弱的能力或活力，被称为“衰老”。
这是我们所有人都会遇到的最令人不快的发现之一：我们必须以这种方式拒绝某些事情（或选择放弃某些机会）。即使我们成功避开了战争，依然无法逃避这种无奈的现实。
无论是意外事故还是疾病，我们最终都会“因年老而死亡”，而且这种死亡的发生率在人与人之间几乎没有差异。
因此，我们在 65 到 80 岁之间死亡的概率非常高。
我们中的一些人会早逝，而另一些人则会活得更长，甚至能活到九十多岁或一百岁。
但是，这种可能性非常小（或者说，成功的几率很低）。
无论我们多么幸运、身体多么强健，我们的生命都存在一个客观的、无法超越的极限。
普通人往往会忘记这个过程，除非有人提醒他们。
我们非常清楚人类会衰老这一事实；多年来，人们一直认为随着时间的推移，人体会逐渐失去活力（即身体机能会逐渐衰退）。
随着年龄的增长，死亡风险增加这一事实是显而易见的。
就像热水壶冷却下来，或者一双鞋子被穿破一样。
他们还假设所有的动物……
很可能其他生物（比如树木），甚至整个宇宙本身，按照自然规律也都会“逐渐磨损”或衰败。
我们日常生活中观察到的大多数动物确实会像我们一样衰老。
如果有机会活得足够长的话……
以及像有故障的手表或太阳这样的机械系统。
根据热力学第二定律，能量确实会逐渐耗尽（不过整个宇宙是否会最终耗尽能量，目前仍是一个有争议的问题）。
但这些情况与人类衰老过程中的变化并不相似。
一块虽然已经损坏（或功能失调）的手表仍然是一块手表，而且可以重新上发条（使其继续运行）。
相比之下，一块旧手表会因为长时间的使用而变得非常破旧、不可靠，最终甚至不值得修理了。
但是，手表永远无法自我修复——它并没有任何“活的”部件，只由金属构成，而金属会因摩擦而逐渐磨损。
曾经，我们能够自我修复——至少能够修复到足以克服除那些瞬间致命的疾病和意外之外的所有伤害的程度。
在十二岁到八十岁之间，我们逐渐失去了这种能力（或：在人生的这个阶段，我们逐渐丧失了某种特定的能力）。
一种疾病：在12岁时就可能让我们倒下（失去健康），而在80岁时则可能让我们彻底失去生命，直接送我们进坟墓。
如果我们能保持十二岁时那样的活力和精力……
大约需要700年的时间，我们中的一半人会死去；再过700年，剩下的幸存者数量又会减少一半。