Depends on how desperate you are? ;) This is a question of the nature of vacuums. Part 1- In the relatively pure vacuum of space, (for this case let's consider it pure please). Can volume of a closed chamber be increased or decreased without force? (other than the friction of materials, but for this purpose consider theoretical no friction) Pulling the plunger would create no pressure difference, so no suction, right, or in a close cylinder, no resistance to volume change right? Part 2 - I am given to understand that you cannot pull a liquid. Displacement pumps i understand to work by using the pressure difference of atmospheric pressure (the weight of air), to push a liquid into an area of lesser pressure, (created by increasing the volume per unit of material) in this case pulling a plunger! Say i have a 100 foot syringe. this syringe has the needle end sealed. let's say there is a cubic inch of air at the end, (the plunger is perfect and has no friction and an impermeable seal, the syringe cylinder is infinitely strong, as is the plunger). When i pull back on the plunger, i require greater and greater force to move the plunger. Will that force plateu and then become effectively constant? - Do i have this right: at equilibrium the pressure = the force with which the molecules are colliding against the plunger/piston and is equal on inside and out. When the plunger is pulled back, the inside molecules are not providing equivalent pressure/collisions and i must provide the extra force. This force is = to lifting the weight of a column of air the thickness of the area of the plunger surface minus the pressure exerted by whatever is in the volume inside the cylinder. Since this will become increasingly negligible, will the force necessary to expand the volume apprach a constant? If i start with nothing at all in the cylinder, will i be able to continue to increase the volume of the chamber with a Constant force of 14.7 pounds per square inch(i think thats standard atmospheric pressure) untill i reach the end of my syringe tube, or will i need to continually increase the force, if so, why. Thanks!