People constantly need to breathe, yet they seem to feel no presence or weight of the air around them. In reality, air does have weight, and the vast atmosphere is the sum of all the air, with even greater weight. So why aren’t people flattened by it?
According to a report from LiveScience, Anthony Broccoli, a professor of atmospheric science at Rutgers University in the United States, stated that the boundary between Earth’s atmosphere and outer space is located about 100 kilometers above the Earth’s surface, with 99.9% of the mass of the atmosphere lying below a height of 48 kilometers.
Broccoli mentioned that the total mass of Earth’s atmosphere is 5.1 x 10^18 kilograms. But why aren’t people crushed by the weight of the atmosphere?
He explained that to some extent, it’s because of the even distribution of air pressure. Air flows around people’s bodies, and ultimately, the air pressure “is evenly distributed across the body, not just downward force.”
However, the pressure exerted uniformly on people’s bodies by the atmosphere is not insignificant. Broccoli pointed out that this pressure is about 14.7 pounds per square inch (equivalent to the weight of a large bowling ball) or 1 kilogram per square centimeter.
Michael Wood, director and professor of quantitative science at Canisius University, explained that people are not crushed by atmospheric pressure because the human body has evolved over time to withstand this pressure.
Broccoli added, “The air inside of us pushes out at roughly the same pressure, balancing the pressure out.”
Christopher Baird, an associate professor of physics at West Texas A&M University, mentioned that this balance of forces only occurs when the air can reach all parts of the body.
He gave an example: if you place the nozzle of a vacuum cleaner on your hand and suck out all the air pressing on your skin, the force your hand feels is the weight of the air.
Wood noted that as altitude increases, the air becomes thinner, causing atmospheric pressure to decrease with higher altitudes.
This is why people experience a popping sensation in their ears when ascending and descending in an airplane – the internal pressure in your ears needs time to equalize with the external pressure, resulting in a popping sensation as the pressure on both sides of the eardrum changes.
Wood also mentioned that the pressure from inside the body is one of the reasons people cannot travel in outer space without a spacesuit.
He said, “The pressure in space is practically zero. Without the pressure exerted on the body, internal pressure would cause the body to expand like a balloon until the pressure is released.”
In addition to pressure resistance, Christopher Mason, a professor of physiology and biophysics at Cornell University in the United States, is developing spacesuits with built-in filtration devices that can turn astronauts’ urine into water for direct consumption during spacewalks.