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What happens to a human being when subjected to space with no oxygen or protective suit? I have seen many explanations but I would like to know the exact reaction. Many Thanks
Answer 1:

Of course, the human being would die, that is the short answer. Furthermore, this would happen very quickly. To go into more detail, there are two main aspects to the surroundings of outer space that make life for humans impossible without appropriate protection or "space suits". One is the absence of oxygen and any gases - space is essentially a vacuum. The other is the very low temperatures in space. And while either of these alone would be enough to kill a human being, the absence of air, the vacuum that outer space is, will probably act faster. As you may know, even at high altitudes such as on the highest mountains on earth or when traveling in an airplane, the air is so thin that a human exposed to this thin air immediately after being on ground level would quickly lose consciousness and die. That is why airplanes have oxygen mask dispensing safety systems (and even so, there have been airplane accidents where these could not be applied quickly enough, and the pilots became unconscious - that's how quickly it happens even in conditions that are less extreme than outer space). And it is also why it is such an incredible feat when people climb 8000m peaks without extra oxygen. For a long time, that was thought of as impossible, because in animal tests it had been determined that if you bring a mouse quickly from sea level to the top of Mount Everest without supplemental oxygen, it will die of lack of oxygen! So a human in outer space would die extremely quickly from lack of oxygen - the vacuum there will even suck out all air from your lungs immediately - and all the other effects of the vacuum there and the low temperature would only be secondary in their effect.


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