Would a human explode in space without a space suit?

Would humans really explode if they accidentally wound up in outer space without a space suit? - Question posed by bornfamous.

No.

What would happen, then?

If you found yourself flung out of a spaceship without a space suit on, the following things would happen to you:

First, the gases in your body in places such as the lungs and digestive system would expand due to a loss in external pressure pushing on your body. The biggest danger from this would be your lungs rupturing and releasing bubbles of air into your blood. If there's anything you can do to improve your chances of survival it's to breathe out as soon as you know you're being chucked out into space- the less gas there is in there, the less damage it can do when it expands.

Next, the low pressure would cause the water in your body to turn into vapour. In the areas of your body with access to the outside universe, the water will just boil away with a cooling effect that will lower the local temperature of these areas almost to freezing point. In more enclosed areas, like your muscles and organs, the expanding water will cause bloating, and some of your body parts may swell up to twice their usual size. Your skin is quite stretchy, so it is unlikely to break, but you will, if rescued, experience widespread bruising due to ruptured capillaries.

Next up is 'the bends'. Deep sea divers are familiar with this condition in which too quick a de-pressurisation causes nitrogen dissolved in the blood to form bubbles of gas. This is quite painful, according to divers who have suffered it.

Under 'normal' pressure you could survive for a couple of minutes without oxygen, but in the very low pressure environment of outer space the gas exchange mechanisms in your body start to work differently and the effects are accelerated. After something in the region of ten seconds, therefore, you will start to lose your vision and your judgement will be impaired. You will become unconscious within the next few seconds, your skin will start to turn blue, and your body will probably start to convulse.

If you are rescued within the next ninety seconds or so, you still stand a chance of survival as your blood pressure will still be high enough for your heart to keep beating and your brain will not necessarily be damaged beyond repair. Beyond this time, your blood pressure will fall low enough that it starts to boil, your heart will stop beating and your brain will suffer irreparable damage.

If you're rescued before this point is reached it is possible that you will make a full recovery, although your sight may take longer to return than other functions.

What won't happen?

• You won't freeze to death. On Earth you can lose body heat quite quickly because there's air or water around to carry it away from you. In space there is no air or water, so there isn't really anywhere for the heat to go, so the process takes longer.
• You won't explode. Your skin is too stretchy and there's won't be enough expanding gases inside you for this to happen. You'll experience bruising, possibly severe, and individual organs may rupture, but the expansion won't be fast or sustained long enough to make you actually explode.
• You won't burn up instantly. You'll get severe sunburn over the course of your two minutes in space, but you won't burst into flames or anything.

For a good idea of what won't happen when exposed to the vacuum of space, you can watch almost any of the scenes that have dealt with the idea in television and the movies. Most are completely unrealistic, and some don't even try to be accurate.