Question

Can pressure be zero?

Answer 1

Not unless literally nothing is in the system.

Apparently, `10^(-12)` `"torr"` has been accomplished (ultra-high vacuum), while interstellar space has around `"1 atom/cm"^3`, but it's certainly not easy for humans to accomplish.

The most straightforward article I could find mentions CERN readily managing `10^(-13) "atm"` of pressure after two weeks of pumping, which is around `7.6xx10^(-11)` `"torr"`. That's pretty good...