why do we not feel the weight of the atmosphere

The atmosphere is a mixture of gases and it pushes on us with atmospheric pressure. Although atmospheric pressure changes with the weather, it is usually about
100,000 N/m. This is equivalent to 100,000 apples piled up on a square metre (it s easy to remember that an apple weighs about a newton). If we stacked up all those apples, they would form a about 10 m tall. So the pressure of the atmosphere is a bit like being under a 10 metre tall pile of apples. Or we could replace the apples with water (apples are mainly water).


So the pressure of the atmosphere is the same as lying under. You just have to go to a public swimming pool and dive to the bottom of the deep end to feel the pressure on your ears! The reverse can also happen. A scuba diver who takes a deep breath and fills his lungs on the bottom of the pool, and goes to the surface with out exhaling can suffer an air embolism (burst lung and air entering the blood stream) due to the pressure of expanding air in his lungs. Yes the earth's gravity causes our atmosphere to be pulled and stay on the earth otherwise it would dissapear like the moon or mars!


The weight of a one inch square column of air at sea level is 14. 7 lbs! As you go higher there is less air above you and therefore the pressure per square inch is less. Pressure does not make us lighter. It is the boyancy of the air that makes us lighter. This is called Boyle's law. If you weigh yourself on a scale, you will measure your mass minus the mass of the volume of air that your body displaces.


This difference is trivial when we weigh ourselves but may not be trivial in precise measurements or scientific experiments. This is also how boats and hot air or helium balloons float. If the pressure is higher, then the mass of the air that your body displaces is also higher and you will be boyed upward a tiny bit more! But this is such a small unnoticeable amount. As far as feeling the effects of pressure, even if you dive very deeply the pressure does not affect the liquid or solid parts of your body but only air cavities such as lungs or sinuses and ears, or air caught in your intestines.


You can experience this also in a plane. I get sinus headaches in a plane! Also when at higher altitudes, because of lower pressure, less oxygen gets pushed across the air/blood interface in our lungs and we have difficulty performing physicaly. we get tired! If you live at higher altitudes for a while, your body will compensate by producing more hemoglobin. Hope this helps. January 8, 2013 by efzauner

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