eli5 Why is a perfect vacuum so hard to create?

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My university has a sputtering machine which is this crazy expensive piece of equipment that has to have a really strong vacuum pump and wacky copper seals and if it loses power for even a minute it has to spend 16 hours pumping it’s vacuum back down.

I know people talk about how a perfect vacuum is like near impossible, but why? We can pressurize things really easily, like air soft co2 canisters or compressed air, which is way above 1 atmosphere in pressure, so why is going below 1 atmosphere so hard? I feel dumb asking this as a senior mechanical engineering student but like I have no clue lol.

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Anonymous 0 Comments

Let’s ignore technical details like when you compress the air, there is room full of air you can take molecules from while pumping for vacuum is like fishing for individual molecules in empty room hoping that you catch one. Let’s look at the numbers instead.

If your airsoft tank drops from 200 atmospheres to 199.9999999, you won’t notice that. If someone tries to create vacuum at **0.000000000001**atm and leak causes it to raise to **0.000000001**001atm, that’s thousand times worse than intended.

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