If you go out into space without your space suit would you expect to explode, snap-freeze or boil?

Dr Stephen Juan: In the 1981 film Outland that starred Sean Connery there was a construction worker who had a torn space suit that leaked, and he swelled up and exploded, and then Keir Dullea in the classic 2001: A Space Odyssey, he blows himself into the airlock from a pod without a helmet but he doesn’t blow up, and the reason is because the air pressure would drop and the human diaphragm could not pull hard enough for normal respiration.

Astronaut floating in space. Copyrighted imageCredit: Used with permission
Astronaut floating in space Image: Clemens Koppensteiner, used under Creative Commons licence.

You wouldn’t explode; your difficulty would be with anoxia (no oxygen), a difficulty in breathing. It would be harder and harder for you to inhale. You could probably last for a few seconds, but you may not even get any trouble until about a minute, and probably in outer space your real exposure would be to the skin, you’d get a sunburn, and if anything is going to boil up, rather than your blood, it would be your saliva.

This is an extract from Breaking Science. Listen to the whole programme, originally broadcast on BBC Radio Five Live, March 2009.

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