For as far back as we can trace our existence, humans have been fascinated with death and resurrection.
从人类诞生开始，人类一直对死亡与复活着迷。
Nearly every religion in the world has some interpretation of them,
几乎每个宗教都对它们有着不同的见解，
and from our earliest myths to the latest cinematic blockbusters, the dead keep coming back.
从早期的神话故事到最新的电影大片中，死者在不断的复活。
But is resurrection really possible?
但是复活真的可能吗？
And what is the actual difference between a living creature and a dead body, anyway?
生物的生与死的区别到底在哪里？
To understand what death is, we need to understand what life is.
要理解什么是死，我们必须先理解什么是生。
One ancient theory was an idea called vitalism, which claimed that living things were unique
有一个被称为“活力论”的古老的理论，它认为生物体是独特的，
because they were filled with a special substance, or energy, that was the essence of life.
因为生物充满特别的物质或能量，这种物质就是生物的本质。
Whether it was called qi, lifeblood, or humors,
不管此物质被称之为气、生命脉或是体液，
the belief in such an essence was common throughout the world,
世界各地普遍深信这种物质的存在，
and still persists in the stories of creatures who can somehow drain life from others,
而且不时可以听到关于它们可以从别的生物吸取生命的故事，
or some form of magical sources that can replenish it.
或是某种神奇的原料可以补充它们。
Vitalism began to fade in the Western world following the Scientific Revolution in the 17th century.
在17世纪的科学革命后，“活力论”在西方世界开始失去市场。
René Descartes advanced the notion that the human body was essentially no different from any other machine,
瑞内·笛卡尔让这种理念更进一步，他主张人类的身体基本上和任何机器并无两样，
brought to life by a divinely created soul located in the brain's pineal gland.
由位于脑内的松果体内的神所创造的灵魂而有生命。
And in 1907, Dr. Duncan McDougall even claimed that the soul had mass,
在1907年，邓肯·麦克道格尔博士甚至主张灵魂是有质量的，
weighing patients immediately before and after death in an attempt to prove it.
他以病人在死亡前后的所称的重量来证明。
Though his experiments were discredited, much like the rest of vitalism,
虽然他的实验，和其他活力理论一样，没有被承认，
traces of his theory still come up in popular culture.
我们仍能在流行文化中找到其理论的踪迹。
But where do all these discredited theories leave us?
除了这些不被接受的理论，那我们还有什么其他的解释吗？
What we now know is that life is not contained in some magical substance or spark,
我们现在知道的是，生命不是被包含在某种神奇的物质或火花内，
but within the ongoing biological processes themselves.
而是不断的生物过程本身。
And to understand these processes, we need to zoom down to the level of our individual cells.
要了解这些过程，我们必须放大到我们的个体细胞上。
Inside each of these cells, chemical reactions are constantly occurring,
化学反应在每一个细胞里不断地在发生，
powered by the glucose and oxygen that our bodies convert into the energy-carrying molecule known as ATP.
由我们身体转化葡萄糖和氧气，成为携带能量的分子，也叫ATP。
Cells use this energy for everything from repair to growth to reproduction.
细胞用这个能量来做修补、成长、繁殖等。
Not only does it take a lot of energy to make the necessary molecules,
制造必须的分子需要消耗许多的能量，
but it takes even more to get them where they need to be.
把这些分子送到需要的地方消耗更多的能量。

The universal phenomenon of entropy means that molecules will tend towards diffusing randomly,

宇宙中的熵现象表明分子有随机扩散的趋势，
moving from areas of high concentration to low concentration, or even breaking apart into smaller molecules and atoms.
它们会从分子集中的地方扩散到分子少的地方，或者甚至分裂成更小的分子和原子。
So cells must constantly keep entropy in check by using energy to maintain their molecules
所以细胞必须不断的保持着‘熵’，用能量来维持它们的分子们
in the very complicated formations necessary for biological functions to occur.
以非常复杂的构造使生物功能得以发生。
The breaking down of these arrangements when the entire cell succumbs to entropy is what eventually results in death.
当细胞屈服于‘熵’，这些机制开始瓦解，最后导致生物体死亡。
This is the reason organisms can't be simply sparked back to life once they've already died.
这也是一旦生命体死亡就不能起死回生的理由。
We can pump air into someone's lungs,
我们可以将空气注入一个人的肺，
but it won't do much good if the many other processes involved in the respiratory cycle are no longer functioning.
但如果呼吸系统中的其他过程都失效了，注入再多的空气那也是无济于事。
Similarly, the electric shock from a defibrillator doesn't jump-start an inanimate heart,
同样的，除顫器的电击也无法重启一个死亡的心脏，
but resynchronizes the muscle cells in an abnormally beating heart so they regain their normal rhythm.
它只能使心跳异常的心脏将肌肉细胞重新同步化，让它恢复正常的律动。
This can prevent a person from dying, but it won't raise a dead body, or a monster sewn together from dead bodies.
这可以防止一个人的死亡，但它不会使人起死回生，更不用说由死尸缝起来的怪物。
So it would seem that all our various medical miracles can delay or prevent death but not reverse it.
所以尽管我们有各种医学奇迹可以延迟或预防死亡，但不能转死为生。
But that's not as simple as it sounds
不过也不能一概而论，
because constant advancements in technology and medicine have resulted in diagnoses such as coma, describing potentially reversible conditions,
因为科技和医药的不断进步，可将如昏迷的诊断为有反转的可能性，
under which people would have previously been considered dead.
在以前会以为好像没救的情形。
In the future, the point of no return may be pushed even further.
在未来，回生乏力的关键点可能可以再向后推。
Some animals are known to extend their lifespans or survive extreme conditions
据我们所知，有些动物可以增长寿命或在极为恶劣的情况下存活，
by slowing down their biological processes to the point where they are virtually paused.
通过放慢他们的生物过程甚至到停止。
And research into cryonics hopes to achieve the same
人体冷冻学的研究就是希望可以达到这个结果，
by freezing dying people and reviving them later when newer technology is able to help them.
借由将濒死者冷冻，当更新的科技可以帮助他们的时候再将他们复活。
See, if the cells are frozen, there's very little molecular movement, and diffusion practically stops.
比如说，当细胞冷冻以后，就几乎没有分子活动，扩散也基本停止了。
Even if all of a person's cellular processes had already broken down,
即便一个人的细胞流程已经瓦解了，
this could still conceivably be reversed by a swarm of nanobots, moving all the molecules back to their proper positions,
想象中仍然可以借由一群纳米机器人反转，将所有分子放回它们的适当位置，
and injecting all of the cells with ATP at the same time, presumably causing the body to simply pick up where it left off.
也同时将ATP注射在细胞里，这也许可以让生命体可以重新运作。
So if we think of life not as some magical spark,
所以如果我们认为生命不是某种神奇的火花，
but a state of incredibly complex, self-perpetuating organization,
而是一种无法想象的复杂和自我延续的组织的状态，
death is just the process of increasing entropy that destroys this fragile balance.
死亡只是熵增过程，破坏了这个脆弱的平衡的过程。
And the point at which someone is completely dead turns out not to be a fixed constant,
一个人完全死亡的关键点不再是一个固定常数，
but simply a matter of how much of this entropy we're currently capable of reversing.
而是简单来说就是目前我们能够扭转多少熵的问题。