Hello everybody, this is slightly embarrassing (for a physics student), but I realized in the last couple of days that I am somewhat confused with the concept of "pressure". Pressure is defined in "school-level" as "force per area". So if I have a plate of 2m^2 on which a downwards force of 3N is exerted, the pressure on the plate is 3/2 N/m^2. Right? First question: What happens if, in the scenario above, I exert the same force in the opposite direction (3N upwards) as well? Is my pressure 0 N/m^2 or 3 N/m^2 (double than before)? The motivation for this question is really somewhat more complex: One says that the pressure on the surface of a star vanishes (P=0) and maximal in its center. Now if I assume I have a massive ball, and I put aside all gas/radiation/whatever pressures and concentrate only on the gravitational pressure, i.e., the force/area exerted by gravitation- Second question: Why should the pressure in the center be maximal? All the forces cancel one another in the "exact center", so that there's practically 0 Force - why not therefore 0 pressure? Furthermore, why is the pressure on the outer layer 0? The force there (on a certain gas element) is GMm/r^2, thus non-vanishing - why shouldn't there be any pressure? What if I'm simply holding a plate floating above the star - doesn't it have gravitation pressure on it? So I've been working with pressure for years now, using it in thermodynamic equations as this quantity that tells me of the force transferred by gas molecules to normal surfaces, ideal gas equation and so one, but I realize, I don't really "dig" the definition of pressure. Can someone enlighten me? Thanks a lot.