Which of the following best describes atmospheric pressure and its cause?

Atmospheric pressure is primarily defined as the weight of the air above a specific point exerting downward force due to the gravitational attraction between the Earth and the molecules in the atmosphere. While gravity is a key factor in this phenomenon, the correct answer encompasses the concept that atmospheric pressure is influenced by the combined weight of all gases in the atmosphere.

The presence of thermal radiation does not directly create pressure but does influence temperature, which can affect air density and thus pressure indirectly. Therefore, the correct understanding of atmospheric pressure involves both gravity and the collective weight of all atmospheric gases. This foundational knowledge is essential for grasping concepts related to flight, weather patterns, and the physiological effects of altitude on the human body. Understanding these factors helps illustrate not only what atmospheric pressure is but also why it varies with changes in altitude and weather conditions.