在科幻小说中常常可以看到这么可怕的一幕：飞船船体破裂，一位船员在毫无装备的情况下被困在太空舱中，而他却要把舱门打开来驱赶太空舱里面的不速之客。缺少太空服的保护，人直接暴露在真空和接近零气压的环境，是不可能长时间存活的。

 

但事实上会发生什么呢？你的眼睛会爆出来吗？你的血液也会迅速的沸腾蒸发？经过上世纪60年代的动物实验和对发生在太空和气压舱的事故总结，我们发现，人直接暴露在太空中的结果并没有我们想象中的那么戏剧性。

暴露在太空中，你首先会注意到的是缺氧，但是你并不会因此马上丧失意识。你的身体会继续利用你血液中的氧气，这大概能维持15秒。如果这个过程中你并没有屏住呼吸的话，你大概可以生存2分钟，而且不会造成永久性的伤害。

但是如果你屏住了呼吸，那你就杯具了。由于大气压的下降会导致你肺里面的气体迅速膨胀，并且把肺部撑破，气体会进入你的循环系统。因此，如果你发现自己突然暴露在真空环境中，你要做的第一件事就是把你肺里面的气体全都呼出来。

还有一件你比较无能为力的事，暴露在太空中大约10秒后，你会发现你的皮肤和组织开始出汗。这是在零气压环境，你体内的液体开始蒸发导致的。不过由于人类的皮肤强度足够强，你并不会好像气球那样膨胀破裂。此外如果你被带回到正常气压的环境，你的皮肤和组织也能恢复到原来的状态。

除非你休克了，不然暴露在太空中并不会影响你的血液循环，因为你的循环系统可以维持足够的血压保证血液的流动。宇航员Jim LeBlanc在1965年的一次空气舱实验中，由于太空服出现漏气，导致他暴露在接近真空的环境中。在本次事故中Jim大约保持了14秒的意识，根据他的描述，暴露在真空中舌头上的水分会沸腾，而他在昏迷前最后的感觉就是舌头上在冒泡。参与实验的研究人员在Jim暴露在真空中约15秒后才发现异常，并及时往空气舱中重新注入空气，Jim也因此获救。

由于缺乏太空服的保护，你会直接暴露在宇宙射线中，这样会导致你严重晒伤，此外你还可能会得减压病。不过，虽然外太空的温度非常低，但你并不会在窒息前被冻僵，因为在缺少对流和传导的情况下热量并不会如此迅速的流失。

如果你最终死在太空中，因为缺乏氧气，你的尸体并不会像地球上的普通尸体那样腐烂。如果尸体比较接近热源，那么最终会变成干尸；否则你将会被冻结。如果你是死在宇航服内，那么将会尸体会腐烂，直至宇航服内的氧气被耗尽。不管以上哪种死法，由于缺少空气，尸体不能被降解，你的尸体都将会保持很长很长一段时间，并且在广袤的宇宙空间漂浮数百万年。

（编译：dalin；via CNET）

What happens to the unprotected human body in space?

It's a recurring horror in sci-fi: the hull is pierced, a human is trapped without equipment in an airlock about to open, a door needs to be opened in order to expel something undesirable. With no air and almost zero pressure, the human body isn't going to last long without some form of protection.

But what does happen, exactly? Do your eyes explode outward while your blood evaporates? Well, no. The truth is both less dramatic and far more fascinating -- as we have discovered through accidents in space and in test chambers, and animal experimentation in the 1960s.

The first thing you would notice is the lack of air. You wouldn't lose consciousness straight away; it might take up to 15 seconds as your body uses up the remaining oxygen reserves from your bloodstream, and -- if you don't hold your breath -- you could perhaps survive for as long as two minutes without permanent injury.
If you do hold your breath, the loss of external pressure would cause the gas inside your lungs to expand, which will rupture the lungs and release air into the circulatory system. The first thing to do if you ever find yourself suddenly expelled into the vacuum of space is exhale.

The other things, you can't really do much about. After about 10 seconds or so, your skin and the tissue underneath will begin to swell as the water in your body starts to vaporise in the absence of atmospheric pressure. You won't balloon to the point of exploding, though, since human skin is strong enough to keep from bursting; and, if you're brought back to atmospheric pressure, your skin and tissue will return to normal.

It also won't affect your blood, since your circulatory system is able to keep your blood pressure regulated, unless you go into shock. The moisture on your tongue may begin to boil, though, as reported by Jim LeBlanc, who was exposed to near vacuum in a test chamber in 1965. LeBlanc's suit sprung a leak, and he remained conscious for about 14 seconds; his last sensation was bubbling on his tongue (he was safely revived, as the researchers began repressurising the chamber almost immediately -- after about 15 seconds).

Because you will be exposed to unfiltered cosmic radiation, you can expect some nasty sunburn, and you'll probably also get a case of decompression sickness.You would not, however, freeze straight away, despite the extremely cold temperatures; heat does not leave the body quickly enough for you to freeze before you suffocate, due to the lack of both convection and conduction.

If you do die in space, your body will not decompose in the normal way, since there is no oxygen. If you were near a source of heat, your body would mummify; if you were not, it would freeze. If your body was sealed in a space suit, it would decompose, but only for as long as the oxygen lasted. Whichever the condition, though, your body would last for a very, very long time without air to facilitate weathering and degradation. Your corpse could drift in the vast expanse of space for millions of years.