The discussion centers on why the atmosphere does not crush humans despite its immense weight. It explains that the pressure exerted by the atmosphere is balanced by the internal pressure of the human body, primarily due to the water content and the air in lungs and cells, resulting in a net force of zero. The pressure at sea level is about 14.7 pounds per square inch, which, while significant, is not enough to cause harm as it acts uniformly from all directions. Rapid changes in altitude can create pressure differences that are felt, such as during airplane takeoffs and landings. Ultimately, the gaseous nature of air and the balance of pressures allow humans to exist comfortably under the atmosphere.