If I take a medical syringe, position the plunger in the middle of the length of the tube and seal off the tip, I will encounter substantial resistance when I try to move the plunger.
But, if I take the syringe into outer space – no atmosphere – and do the SAME procedure will I notice NO resistance when moving the plunger?  Since there is no air to compress or decompress I suspect there will be no resistance.  Is this correct?

Asked George Creegan

Answer

Yes, the only thing keeping you from pulling the plunger on a syringe with a sealed end is the surrounding air pressure.    If there is perfect vacuum inside and outside the syringe!