Let us calculate the atmospheric pressure on the cubic Earth.
The atmospheric pressure at the ground level is determined by the mass of the atmosphere piled on the ground. The pressure increases with the mass of the atmosphere [Fig. 1(a)]. On the other hand, atmospheric pressure decreases with altitude. The rate of decrease depends on the air temperature [Fig. 1(b)]. Therefore, the distribution of atmosphere on the cubic Earth depends on the air temperature.
Let us assume that the air temperature at the ground level is 27℃. Then, the atmosphere is piled on the cubic Earth as shown in Fig. 6. The ground pressure at the center of a square is 310 atm. It is an amazing world of the high pressure. Human being cannot live in such a high pressure. The pressure decreases with altitude. It is 1 atm at the altitude of 50 km.
On the other hand, looking at the horizontal distribution of the pressure, we notice that it decreases outward from the center of the square. It is 1 atm 700 km distant from the center. We can live around the area with 1atm where the atmospheric environment is similar with that of the real Earth. If you go further outside of this area, atmospheric pressure decreases until 0.5 atm at the distance of 750 km. We cannot live without an oxygen mask. The atmosphere becomes thinner and thinner outward and few air exists before you reach the edge of the square. This means that the atmosphere on the cubic Earth is located near the central part of the side of the cube as shown in Fig. 3(a).
Where do we find creatures on the cubic Earth?
If creatures similar with those living on the real Earth are living on the cubic Earth, they are expected to live in a zone between 700 km 〜750 km distant from the center of squares. This is the habitable zone of living beings. If you go to the next side of the cube, you must pass the area without the air. Thus, you need a space suit for travel to the next side.