Question

Why does the atmospheric pressure go on decreasing as we go higher up above the earth's surface?

Answer 1

At sea level, the air layers are denser (more density), so it applies greater pressure. Hence, the pressure is higher at sea level and it reduces with the altitude because the air becomes thinner and exerts less pressure. Density plays an important role in observing the pressure.

Complete step by step answer:
Air in the environment is not equivalent at all levels. The air consists of molecules, and though very light, they do have weight. It is denser near the earth. It goes on thinning out as we move up.
The density of air becomes heavier near the earth's surface. It begins to diminish as we move to higher altitudes and ultimately leads to space, i.e., outside the earth's atmosphere. So, there is more air close to earth; there is more air pressure. As the amount of air reduces, its weight and the air pressure decrease consequently. The extra pressure pushes the air molecules closer collectively, following in more mass in the given volume. Thus, the atmospheric pressure is increased at lower altitudes, the density being higher. The atmospheric pressure is low at higher altitudes, the density being lower.
Thus, atmospheric pressure goes on decreasing as we go higher up above the earth's surface.

Additional Information: Atmospheric pressure depends on the temperature also. When the temperature increases in an area, the air becomes thinner and rises; thus, low-pressure forms fill up the void and neutralize that low pressure; cooler air decreases in that area.

Note: With the increase in height, the length of the column of overlying air on the earth's surface decreases, and hence the weight or pressure applied by the atmosphere reduces. Total pressure also depends on the change in partial pressure of its elements such as Oxygen, Nitrogen, etc