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Nature of gravity

  1. May 2, 2009 #1
    does the effect of gravitational force vary with state of matter,i.e
    the force is most felt in gases?right.
    anything having mass experiences gravity,so 2 gases having masses should experience gravity between themselves.
  2. jcsd
  3. May 2, 2009 #2


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    Yes, gasses are affected by gravity, as is everything with mass.
  4. May 3, 2009 #3
    then moon's gravitational pull has to affect gases also,only the water bodies are affected causing tides,why ?
  5. May 3, 2009 #4
    I think you will find that the earths atmosphere does go through tidal variations as does the solid parts of the earth.
  6. May 3, 2009 #5
    Anything that has mass is indeed affected by gravity.

    F = G(m1m2)/r^2

    Gas is mass. It's not very dense, but it is still mass.
  7. May 3, 2009 #6
    Light (low density) gases tend to rise above heavy (high density) gases. CO2, with a gram molecular weitht of 44 grams per Avagadro's # of molecules, will sink in stagnant air and sometimes asphixiate people (see http://en.wikipedia.org/wiki/Lake_Nyos). Water is about 800 times more dense than air.
  8. May 3, 2009 #7


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    If gases were not affected by gravity, the Earth would not have an atmosphere and we wouldn't be here writing about this! :eek:
  9. May 4, 2009 #8
    That's exactly right jtbell. I should have thought of posting that fact. That is probably the best example/proof that gases are affected by gravity. The Earth's gravity is what holds our atmosphere in place. The same is true for all celestial bodies with atmospheres. It explains why the moon and mercury do not have atmospheres. They are too small for their gravity to hold one.

    Excellent point made!
  10. May 5, 2009 #9
    mass or energy is affected by gravity.
  11. May 5, 2009 #10
    No, only matter is affected. Gravity could be thought of as a type of energy, but a force is simply a perpetual energy exerter.
  12. May 5, 2009 #11


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    None of that is correct. [edit] Well, maybe the part in the middle, but it would be a real stretch - like calling a spring a type of energy.
  13. May 6, 2009 #12
    A compressed spring has potential energy and has more mass when compressed .
  14. May 6, 2009 #13
    What about light.
    Passing starlight has been observed to be bent by the sun yet it don't have mass only energy.
  15. May 6, 2009 #14
    yes light is affected by gravity it also creates gravity.
  16. May 6, 2009 #15
    it is obvious that light is affected by gravity,thats how shift occurs.
    now when the moon exerts its gravitational pull on earth,it is the gases that need to
    be affected first,rather the liquid bodies.but tides are being created whille atmosphere
    seems to be intact.
  17. May 6, 2009 #16


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    What do you mean by "first"? They are bouth affected simultaneously.
    The oceans seem to be intact as well. The height of the water surface changes by a few meters only. Since the atmosphere doesn't have a distinct upper surface it would be hard to detect such an effect on it.
  18. May 6, 2009 #17

    Is this true? Light creates gravity?
  19. May 6, 2009 #18
    Gravity (i.e., mass or weight) is not a conserved quantity. For example, when a positron annihilates at rest with an electron, the gravity (mass) associated with the 1.02 MeV in rest mass is lost. Some measurements have been made on the gravitational attraction of low Z materials (e.g., carbon, which is half neutrons) vs. high Z (e.g., lead, which is 60% neutrons), but the measurements are not conclusive on neutron vs. proton gravitational attraction.
  20. May 6, 2009 #19
    well," first", i meant in priority,gravitational pull would be more over gases or liquids?
    according to the formula,does increase in mass mean increase in force of gravity?
  21. May 6, 2009 #20
    sorry to post again, do we know the rate at which gravity acts?
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