[jambutty]

Originally Posted by Neil

You need to understand what suction is to see why they asked the question and why they gave the answer they did. Suction - Wikipedia, the free encyclopedia

If you have two containers of differing air pressure and they are connected the air pressure will equalize in both. Whether it is sucked in or pushed in is a moot point and dependant on whether you are in one container or the other. If you are in the low pressure container the air is being sucked in. If you are in the high pressure container the air is being pushed out and if it is being pushed out of one it can be said to be pushed into the other.

It’s a bit like when you mix hot and cold water. Does the hot water make the cold water warmer or does the cold water make the hot water cooler.

The bottom line is that it is the movement of the piston that creates a vacuum and this vacuum sucks in the air. If the piston did not move the air from outside would not push it down.