Atmospheric pressure is defined as what?

Atmospheric pressure is defined as the weight of all the gases and molecules in the atmosphere acting upon the Earth's surface. This pressure results from the gravitational pull of the Earth on the air above, which creates a column of air that exerts force on the surface. Atmospheric pressure is generally measured using a barometer and is expressed in units such as pascals, millibars, or inches of mercury.

Understanding this concept is crucial because it links to various atmospheric phenomena, weather patterns, and the principles of fluid dynamics. For instance, as altitude increases, the amount of air above a given point decreases, leading to lower atmospheric pressure, which is why climbers at high altitudes often experience symptoms of altitude sickness due to reduced oxygen availability.

The other options provided do not accurately define atmospheric pressure; for instance, the pressure exerted by the sun does not directly relate to atmospheric pressure, nor does the pressure from ocean waves or air pressure in a confined space capture the comprehensive weight of the atmosphere's gases affecting Earth's surface.