Why is atmospheric pressure the same indoors?

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SUMMARY

The atmospheric pressure indoors remains at approximately 101 kPa due to the principles of pressure being a state function dependent solely on elevation, not the presence of a ceiling. Even with a ceiling overhead, the pressure is exerted uniformly in all directions, ensuring that the pressure felt at the top of the head remains consistent with that experienced outdoors. The concept of a density gradient of air, with higher density at ground level, further clarifies why indoor atmospheric pressure does not fluctuate despite the limited air column above.

PREREQUISITES
  • Understanding of basic physics concepts, particularly pressure as a state function.
  • Familiarity with atmospheric pressure measurements (e.g., 101 kPa).
  • Knowledge of air density gradients and their implications.
  • Basic comprehension of how pressure is exerted in all directions.
NEXT STEPS
  • Research the principles of hydrostatics and how they relate to atmospheric pressure.
  • Explore the concept of air density gradients and their effects on pressure at different elevations.
  • Study the behavior of gases under varying pressure conditions using the Ideal Gas Law.
  • Investigate the effects of airtight environments on atmospheric pressure and air movement.
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Students of physics, educators explaining atmospheric pressure concepts, and individuals interested in understanding the behavior of gases in different environments.

mcmath
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Hi, apologies in advance as I feel stupid for asking this, but believe me I tried googling. The typical explanation for atmospheric pressure is that there is a column of air sitting on us, creating a pressure of 101 kPa. But what if there's a ceiling above us? Now only a few feet of molecules is directly above our heads. Why doesn't atmospheric pressure change? I remember vaguely from a physics course that it's related to pressure being a state function only dependent on elevation, and that pressure is applied in all directions at the given elevation. So I can understand that my arms may feel the 101 kpa pressure, but if I'm indoors, why does the top of my head still feel the same 101 kpa pressure?
 
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mcmath said:
The typical explanation for atmospheric pressure is that there is a column of air sitting on us, creating a pressure of 101 kPa. But what if there's a ceiling above us? Now only a few feet of molecules is directly above our heads. Why doesn't atmospheric pressure change?
Imagine you pumped all the air out of your house. Is your house air tight? What keeps the air from pouring off the roof of your house and in through the cracks between your front door and its frame?
 
ok, so I guess a better explanation of atmospheric pressure is that there is a density gradient of air, with the density being heaviest at ground level?
 
I guess my main point of confusion is when people explain atmospheric pressure to me as a column of air above our heads, extending miles into the air, which would mean the 101kPa pressure is from the billions of air molecules pressing down on my head, which makes sense only if you're outdoors
 
mcmath said:
I guess my main point of confusion is when people explain atmospheric pressure to me as a column of air above our heads, extending miles into the air, which would mean the 101kPa pressure is from the billions of air molecules pressing down on my head, which makes sense only if you're outdoors

Well, this column likes to seep through any tiny crack and push in from all sides.
 

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