eli5 Why is a perfect vacuum so hard to create?

703 views

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.

In: 3143

15 Answers

Anonymous 0 Comments

There’s no such thing as *sucking*.

A pressure differential *pushes* fluids from one place to another.

If there is almost nothing inside of the container you want to make into a vacuum, there’s almost nothing to push the molecules (or atoms?) of the material out of the container.

Say you’ve got a box that has 20 molecules of Oxygen in it, and you want no molecules of Oxygen in it. Those molecules have to push one another out of the container, but they are so few they basically never interact. There’s no other physical force that will move them out of the container.

You are viewing 1 out of 15 answers, click here to view all answers.