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Just how strong is the Air pressure

  1. Apr 6, 2015 #1
    .

    So, how does Air Pressure 'works' on Earth.
    Would this right to say that, the air molecules present in the atmosphere are forced down due to gravity and thus applies force on every object downwards towards the Earth's core thus causing Air pressure?.

    Another question I would like to know the answer of , is how do we even maintain stability at such intense amount of force acting on us everytime?
    I mean our body exerts force from the inside resisting us from Crushing due to Air pressure, what about our own gravity which is trying to collapse ourself from the inside. How are we resisting that?

    Also, I've heard that after coming back from the space you're bone density is lessened and other factors happen causing you to get weak. So if we have less inertia we can't resist much to Air resistance, so can I expect that if someone/something with very low inertia is expected to get crushed by the Air pressure? If this statement is true then I guess we will get daily reports of "Air Crush", but it's not true.So how??
     
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  3. Apr 6, 2015 #2

    Simon Bridge

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    Air particles are warm so they jiggle about, they bump into things, transferring momentum, this bumping is experienced as air pressure.
    The earth has air at all because gravity can hold it down.

    Our own body produces enough internal pressure to oppose the pressure of the air and our own gravity ... our own gravity is easily balanced by electrosctatic repulsion between atoms and molecules just like you dont fall through the floor.

    Inertia has nothing to do with resisting air pressure... reduced bone density can make your bones more brittle, so you could have a hard time standing against gravity. Also see oesteoporosis.
     
  4. Apr 6, 2015 #3

    phinds

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    No, air pressure is uniform in all directions, not just downwards.

    We evolved in it and our bodies are completely accustomed to it.

    true

    inertia is something totally different and has nothing to do with air pressure or bone density
     
  5. Apr 6, 2015 #4

    Simon Bridge

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    Air pressure decreases with height... the pressure from above is less than the pressure from below. If the difference (times area) is more than the weight of the object, it is said to float. The effect is more pronounced in denser fluids like water... over small distances the air pressure can be treated as uniform in all directions.
    Air pressure can also vary with the weather.
     
  6. Apr 6, 2015 #5

    DaveC426913

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    Because things created upon the Earth do not do so by starting off with a vacuum inside. They start off in the presence of normal air pressure (or, sometimes, a lot more pressure).

    By analogy, if you took a flat piece of paper and origami'ed it into a closed box, you would not expect it to suddenly implode.


    The gravitational force of a 50kg object is very, very small.
     
  7. Apr 7, 2015 #6
    Do not forget to take into account the rotation of the planet, which causes winds. If you were in a room, with no wind, at sea level, you would experience 14.7 pounds of pressure per square inch. Not just downward, but from every direction.
    Our biology has evolved to the point where it can adapt to a particular environment. We have vertebrae and internal bones, instead of an exoskeleton, to deal with 9.8 m/s2. If you really want to know how we evolved to resist one atmospheric pressure or one gravity, then you will need to study 540 million years of biological evolution.
    That is true. Long exposure to a weightless environment causes loss of bone density, and certain muscles begin to atrophy because they are not being used. Legs, for example, are rarely used in a weightless environment. Another serious factor, once we leave low-Earth orbit, will be solar and cosmic radiation. Biology and that kind of high energy radiation typically do not get along. They are already being subjected to the same 14.7 pounds per square inch on the ISS that you or I are subjected to at sea level.
     
  8. Apr 7, 2015 #7
    But inertia is the force exerted by the body to remain at the state of rest , resisting external forces. So Considering Air pressure as the external force isn't our inertia too acting against us being crushed by it?
     
  9. Apr 7, 2015 #8
    Can you explain it more clearly?, about how we resist our own gravity.

    So, Is there any specific ratio of how much the 'Inner gravity' would be according to the object's mass. We evolved to it, so can I say that our ancestors had a hard time facing with gravity?

    If the cause of "jiggle effect" of Air particle due to exposure to heat, then would there be no Air pressure if there is no source of heat ?
     
  10. Apr 7, 2015 #9

    phinds

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    You keep talking about gravity when I think you mean pressure, and no, our ancestors did not have any problem with either one. The evolved IN it, after all.
     
  11. Apr 7, 2015 #10
    As others have said, life on this planet including human life, has evolved to be adapted to the Earth environment.
    The environment includes atmospheric pressure, gravity, and other things.
    The prevailing atmospheric composition would be another one, as would be the solar radiation level, and probably more as well.
     
    Last edited: Apr 7, 2015
  12. Apr 7, 2015 #11
    It really isn't so intense. The Venera landers on Venus got crushed (and melted, but that's a different story) after a few hours on surface because the Venusian atmosphere is so much denser than ours. Keep in mind the gravity there is pretty much the same as here, so just focus on air density. Same thing would happen to you if you went down the ocean. You wouldn't survive in either environment. Structurally, we're perfectly built for living here. The strength of the materials in our body and their shape is just right.

    That sounds like an absolute-zero scenario, which is not possible.
     
  13. Apr 7, 2015 #12

    Chronos

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    An astronaut in space is still surrounded by air just like s/he is on earth. In fact, the air pressure maintained in the ISS, or a space suit, is comparable to atmospheric pressure on earth. Human beings do not react well to exposure to a vacuum. Unpleasant things occur, like ebullism and severe flatulence.
     
    Last edited: Apr 7, 2015
  14. Apr 7, 2015 #13
    No sir, the one which you quoted was assuming if there is any specific ratio of an object's mass and it's own gravity. Or Would saying this be correct that Our mass M ∝ Our own gravity. And I see, we evolved IN it.
     
  15. Apr 7, 2015 #14
    I thought there is no gas present in space , it's totally empty except the Celestial objects and gases near these objects. And yes I've heard about how "human" would react to direct exposure to Vacuum, thanks for reminding me though :smile::wink:
     
  16. Apr 7, 2015 #15
    Yes we, humans and other stuff, evolved in the environment that we are in.
    We could imagine living somewhere else, like Mars, but why really?.
    I do not see a real possibiilty of interstellar 'colonisation', for Homo Sapiens, but I am prepared to be wrong about that.
     
    Last edited: Apr 7, 2015
  17. Apr 7, 2015 #16
    Well, there isn't any specific proofs for that though #rootone
     
  18. Apr 7, 2015 #17

    phinds

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    No, you can't prove a negative. If you want to colonize a planet other than Earth, even one in out own solar system, you can certainly hypothesize that it can be done but unless you can prove it, or come very close, you are wasting your time.
     
  19. Apr 7, 2015 #18

    DaveC426913

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    It is true. Your body is under the influence of the gravity caused by your mass. It is pulling you inward.
    But consider: so is a feather in your hand. Or ping pong ball, or paperclip. They are all attracted toward you by your own gravity.

    Do you see any of them flying toward your body and sticking to your stomach?
    No. Because the gravity from a mass of human scale is vanishingly tiny. It's measurable, but you'd need instruments to detect it.

    Gravitational attraction is not a significant force to contend with until you are dealing with objects the size of city blocks or more.
     
  20. Apr 7, 2015 #19
    No there are not.
    Your application for intergalactic social support has been accepted, and we will try to find suitable housing for you.
     
  21. Apr 8, 2015 #20
    You mean to say our own gravity is slowly replinishing!? :nb):nb)
     
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