Hi all, i was pottering away at work yesterday and realised just how little i truly understand about vacuum!! So i have a question, i have a piston in a cylinder, the piston is fully in the cylinder so there is very little air space and the cylinder port is blocked off, the piston has an area of 1 square inch. Now my mind says that due to atmospheric pressure there is 14.7 pounds of force on the back of the piston so if i apply a force in the opposite direction to atmoshperic pressure (i.e trying to pull the piston out) of more than 14.7 pounds it should move out generating a higher and higher vacuum but obviously it doesn't?!? So why not? i can logically see that of the cylinder had a perfect vacuum inside it would be hard to define how that nothingness could expand to take up the extra space but... as you pull on the piston and it starts to form a vacuum in the cylinder it becomes near enough impossible to pull the piston any further yet it still only has 14.7lb of force pushing against it?? Please help my confused brain!