1. The problem statement, all variables and given/known data Some regions of interstellar space is made of lone hydrogen atoms with a density of 1 particle / cm3, at a temperature of around 3 K. Calculate the pressure due to these particles. 2. Relevant equations P = nkbT, where P is the pressure, n is the number density and T is the temp. 3. The attempt at a solution n = 10-6 T = 3 So, P = 4.14 X 10-29 Pa. The gas is not contained in a container, so are we assuming an imaginary surface within which lies a certain quantity of hydrogen atoms and then calculating the pressure exerted on that imaginary surface by the atoms? This interpretation seems to make sense to me because the volume of the surface is independent of the pressure, as seen from the original equation. What does everyone think?