A unit of pressure defined as the average pressure at sea level on Earth.The atmosphere is a unit of pressure defined as the average pressure exerted by Earth's atmosphere at sea level. It provides a convenient reference point for comparing pressures in various contexts, from weather systems to industrial processes. One standard atmosphere is approximately 101,325 pascals, or about 14.7 pounds per square inch.
The concept of the atmosphere as a pressure unit was formalized in the early 20th century, building on Torricelli's barometer experiments in the 17th century. The standard value was later defined precisely by international agreement.
The pressure at sea level arises from the weight of the air column above a given point. This weight compresses the air below, creating a force per unit area. The atmosphere unit simply standardizes this average value, allowing scientists and engineers to express pressures relative to a familiar baseline.
It is used in meteorology for weather forecasting, in engineering for calibrating pressure instruments, and in physics for describing conditions in planetary atmospheres, such as the thin atmosphere of Mars or the dense clouds of Jupiter.
The pressure at the bottom of the Mariana Trench is over 1,000 atmospheres, equivalent to the weight of about 50 jumbo jets on a single square meter.
