(or 10): How does a vacuum work? Why does gaseous matter feel pressured (pardon pun) to occupy as much space in a vacuum as possible?

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Reading The Martian and thinking about things like depressurisation – why does air from a higher concentration feel the need to rush through a small leak with enough force to rip or blow things apart instead of staying put?

What calls it from the vacuum for it to be so obsessed in doing so?

In: Planetary Science

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Anonymous 0 Comments

Gas is a statistical model. The theoretical model of a gas is just a bunch of particles moving in straight lines until they bump into something, like the walls of a container or other gas particles, at which point they bounce off that thing and keep going in a different direction. Phenomena like temperature and pressure are the *averages* of the speed etc. of billions and billions of these particles but individual gas particles are still just flying about in straight lines until they bounce off something.

In a pressure leak situation you can imagine that there are a billion particles bouncing off any given 1 cm^(2) patch of wall each second on the high-pressure side (these numbers are wildly not to scale) and there are only a thousand bouncing off the low-pressure side. If we remove that 1 cm^(2) patch those 1 billion particles from the high pressure side that would have hit it just don’t, and keep going, into the low pressure side. Some may bounce off the thousand particles coming the other way from the low pressure side but even if every one of the thousand low-pressure side particles intercepts a high-pressure side particle, there is still nine-hundred and ninety-nine million, nine-hundred and ninety-nine thousand particles going from the high-pressure side to the low-pressure side and in comparison none going the other way.

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