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Is it possible to calculate earth's massiveness

  1. Apr 7, 2010 #1
    Hi everyone,

    A question that a religious person posed infront of me, he said that the gravity of earth is so perfect that we have gaseous oxygen in the atmosphere. other wise if it were little less earth would be incapable of holding the atmosphere and if it were to much, there would be no gaseous oxygen ... in his view it is gods divine plan ... so i thought about calculating how much variation in earths mass would create liquid oxygen ... to know how precise is the gods plan anyways.

  2. jcsd
  3. Apr 7, 2010 #2
    Indeed, from all the planets in the habital zone around all stars in all the galaxies in the universe. It's amazing that we have a planet that seems perfectly right for us.

    Forget the fact that we've evolved to suit the damn planet. If the planet were different, no doubt we would be different. In that eventuality we'd still be amazed at how the planet is suited for us.

    Cause does not follow effect. The argument also comes from the horribly narcissistic prospect that obviously we are the only reason the planet should exist.
  4. Apr 7, 2010 #3
    Well said. pankaj should note that oxygen is *very* reactive gas and, without life which is creating it in elementary form, I believe it would be gone in (geological) instant.

    Here you have phase diagram of oxygen:


    so, you would need 50 atmospheres to turn in super-fluid at room temperature. In terms of earth mass (to which surface acceleration is directly proportional to) - increase of 50 times. Looks to me god's design is not so sharp after all. Long story short, that guy is full of b.s. :devil:
    Last edited by a moderator: Apr 25, 2017
  5. Apr 7, 2010 #4


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    In general, using "scientific" arguments to "prove" a religion is in all cases misguided, as vague religious statements are in general not open to falsification.

    In this specific case, you can even invoke a variant of the anthropic principle: any sentient, concious, thinking living being must automatically live on a planet that allowed for the evolution of sentient, conscious, thinking living beings. So to discover that you are living on such a planet is not the slightest bit surprising :smile:
  6. Apr 7, 2010 #5

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    I don't think you're reading that right. At 160K (very cold) you need about 80 atmospheres, and extrapolating gets you to something like 200,000 atmospheres.

    In any event, long before the earth became massive enough to liquify oxygen with gravity it would become a gas giant.
    Last edited by a moderator: Apr 25, 2017
  7. Apr 7, 2010 #6
    I wrote 50 atm. because that is oxygen critical pressure and you need at least that. And because I was lazy to extrapolate :)

    But how did you come up with 200,000 atm.? Looks kinda high. You made linear extrapolation above critical point? As far as I can remember, phase transitions line above critical point just continues like 1. order transition line below c.p., so let say T^(1/2) against ln P would provide lower estimate of ~ 4,000 atm.
  8. Apr 8, 2010 #7
    To convert oxygen into water at atmospheric temperature 300 K, pressure required is 5 GPa or 5000 MPa. See link http://en.citizendium.org/images/thu...se_diagram.png [Broken]
    Atmospheric pressure is 0.1 MPa. So, 50,000 times more pressure is required to convert oxygen into liquid. So it is required to increase the weight of vertical air column by 50,000 times. To increase the weight of air column, acceleration of gravity is required to increase 50,000 times more so, it is 9.81 * 50,000. To increase gravity acceleration g= G * M/R. G= universal gravity const. M & R are mass & radius of earth. Here we assume that as mass of earth increases there is no increase is radius, only increase in density of earth. So, mass of earth required 50,000 times more than exist now.
    After this also only lower layer of air undergo this much higher pressure & so oxygen is converted into liquid. Above this layer weight of air column is decreases & so air pressure is also decreases so oxygen on layer above not converted into liquid.
    Here we take only atmospheric pressure is equal to oxygen pressure but it is required to take partial pressure of oxygen into consideration. Oxygen present into air is 21% say fifth part of all gases. So partial pressure of oxygen is fifth part of 0.1 MPa. So, to convert it into liquid five times more pressure & so five time more gravity acceleration & so mass required. So, mass of earth required 50,000 * 5=2,50,000 times more.
    If, we take earth of only mass of 50,000 times more, than also if liquid oxygen put in open atmosphere, it is not converted into gas immediately, because only top layer of liquid oxygen undergo partial pressure of oxygen (Fifth time of atmosphere) & so start converted into gas. But the layer below this undergo pressure of oxygen is equal to atmosphere pressure because it is surrounded by liquid oxygen, so it remain liquid.
    Last edited by a moderator: May 4, 2017
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