I think you're going to hate me for talking again about the vacuum. Yesterday I saw a TV program about CERN. A physicist (spanish by the way) talked about the vacuum is not so vacuum as we could think. Let's suppose I have a reservoir in which it has been made a high vacuum. A manometer measures 1e-5 Pa. Surely the manometer has an instrumental error so maybe that measure has some internal error. I suppose that physicist do not try to explain vacuum from manometers, so the first question is: 1. how can be sizable the small perturbations of the vacuum? What instrumental have used the physicist to know that the vacuum is not so vacuum? Or is merely a theoretical assumption? 2. The same physicist said (translated into english) the next: "the mass is caused by the friction against the vacuum". What does it mean?. Thanks. I'm only a layman in this part of physics.