wargolem

The question that is haunting me about all this is the assumption of a negative pressure inside the bottle. How is it that when you screw the cap back on the 2 liter bottle partially filled with soda (coke), that you are sealing in a vacuum? (negative pressure is a vacuum is it not?) It seems that everyone who is saying that you have a negative pressure is saying that something that is capped at atmosperic pressure suddenly becomes a negative pressure and i am wanting someone to back that up. I understand the people who are saying that "over time" the bottle will pop back to its original shape, that would make sense, but it is because of the gas escaping solution to find equalibrium with the gas above it that causes this, and therefore this implies that you are adding gas to a finite system which will INCREASE pressure which in turn will exert a force on the inner wall of the 2L bottle pushing it out to its original form. I may be wrong here but if there is a negative pressure inside a closed system, then it would want to cause the 2L bottle to further collapse instead of expand would it not?