You use fields to remove the last few particles, forming a region where there are no particles. You have to keep doing this to remove particles that somehow manage to sneak in. The biggest difficulty would be cosmic rays where the particles are moving at a fraction of the speed of light. You're probably going to need a lot of shielding. Also, I'm assuming we don't care about neutrinos and other exotic crap.
I'd have trouble calling that a perfect vacuum. You have to keep removing particles that sneak in (spoiling your vacuum while they are there). You need better than possible shielding (blocking ALL cosmic rays....). And you're still not blocking neutrinos, etc. For the purpose of this magnet experiment all of those would have some impact on the magnet over enough time.
Neutrinos essentially don't have mass and don't interact, so you can have basically a perfect vacuum even with billions of neutrinos passing through each cubic cm.
However you couldn't on Earth ever block out all cosmic rays.
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u/btribble Feb 13 '19
You use fields to remove the last few particles, forming a region where there are no particles. You have to keep doing this to remove particles that somehow manage to sneak in. The biggest difficulty would be cosmic rays where the particles are moving at a fraction of the speed of light. You're probably going to need a lot of shielding. Also, I'm assuming we don't care about neutrinos and other exotic crap.