One possible explanation of the dramatic changes of the Earth.

Discussion in 'Earth Science' started by Emil, Aug 16, 2010.

  1. florian Debunking machine Registered Senior Member

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    I made a graph using Chipz's formula (see post #49) to make a visual comparison with Emil's data given in post #1 :

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    The calculated data used to make the graph are downloadable here (excel workbook): http://tinyurl.com/3opt2tt

    Obviously, Emil's calculations were correct. You owe him an apology.
    Hopefully, it will be a lesson for you.
     
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  3. Ophiolite Valued Senior Member

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    No. I owe you a frigging cheque with which to take some frigging basic maths and physics classes.
     
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  5. florian Debunking machine Registered Senior Member

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    Does it mean that you persist?

    This the Python program I wrote to make the calculations:

    And a sample of the terminal output:

    Conclusion: The centrifugal acceleration balances gravity when the rotation rate is 17 fold the current rate, i.e when the length of the day is 1.41 hours.

    You owe Emil an apology, and now you owe me an apology.
     
    Last edited: Aug 16, 2011
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  7. eburacum45 Valued Senior Member

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    Florian is correct, as far as his calculations go; but another factor that should be taken into the calculation is the fact that a fast-spinning planet would be oblate, therefore the equator would be further from the centre of gravity than the poles. It is a bit tricky to calculate just how oblate the Earth would be if it were spinning very fast, but it would significantly decrease the apparent surface gravity at the equator, adding to the decrease caused by centrifugal force.

    Here's a reasonably plausible guess at the shape of a planet spinning at a rate of once every 2 hours 30 mins;

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    the gravity at the poles is twice as strong as the apparent gravity at the equator.


    Could the Earth have once rotated as fast as this? Well, that is possible, but only very briefly, four billion years ago soon after it formed. Tidal interaction with the Sun and Moon would rapidly have slowed it down within a few hundred million years.

    There is no possible mechanism that could have speed the Earth up more recently (during the Mesozoic, for instance) and no evidence for faster rotation at that time.
     
    Last edited: Aug 21, 2011
  8. florian Debunking machine Registered Senior Member

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    To be correct, that is Emil's calculations.

    I focus on the calculations because it was the point vehemently attacked, notably by Ophiolite.
    By the way, I wonder now who is "an insult to science to the scientific method and to logical thinking", "look like a fool", and need to "take some frigging basic maths and physics classes".
    Let's see if Ophiolite will finally apologize for his unacceptable misconduct.

    You are absolutely right. A fast spinning planet would certainly be oblate and this would lead to an even lower surface gravity at the equator. I guess that there is also an upper limit for the rotation rate, above which a planet is no more stable (depending on its composition, elasticity).

    Not sure, because if the tide frequency is too high, the tidal torque can be significantly reduced (See Webb 1992).
    But there are no evidence for a fast rotation rate whatsoever.
     
  9. eburacum45 Valued Senior Member

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    1,297
    I should point out that I certainly do not endorse any suggestion that the Earth has rotated rapidly at any time in the last three billion years. Any theory about the characteristics of our planet and its lifeforms must look elsewhere for explanations; the day length of Earth in the Devonian Period was around 21.8 hours, and the planet has been slowing down more or less gradually ever since, because of tidal interactions. At no point in that time was the Earth rotating fast enough for centrifucal force to make a significant effect on apparent weight.

    No possible impact could have sped the Earth up at any point in the meantime without imparting so much kinetic energy to the crust that every living organism on our world would have been boiled.
     
  10. Ophiolite Valued Senior Member

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    9,232
    I continue to dispute your claim that the force of gravity is wholly offset by centripetal accelration at an approximately 1 1/2 hour rotation period. Until I have redone those calculations to my satisfaction I shall withhold such an apology. If they are confirmed you and Emil will have a comprehensive apology. Such an apology will not alter the fact that Emil is a nutter and you are half way there. (Maths are not required to establish these facts.)
     
  11. florian Debunking machine Registered Senior Member

    Messages:
    305
    I completely share this view, except for the certitude about the day length during the Devonian, because it is derived from the assumption of a constant revolution period of Earth. I discussed this point ad nauseam in a different thread.
     
  12. florian Debunking machine Registered Senior Member

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    Very good.
    Let's see how much time you need to make these multiplications.
     
  13. wellwisher Banned Banned

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    5,160
    The core of the earth spins faster than the surface according to experiments done by NASA. The assumption of the earth's rotation being due to lingering rotational inertial from its early formation is incorrect. A faster spinning core and a viscoplastic mantle means the surface rotation is a continuous induction, which should generate some mantle heat.

    http://www.usatoday.com/tech/science/discoveries/2005-08-25-core-spin_x.htm
     
  14. florian Debunking machine Registered Senior Member

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    305
    Why? If the tidal torque applies mostly to external shells, isn't it expected that the core would spin faster?
     
  15. eburacum45 Valued Senior Member

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    1,297
    I'm lazy, so I just use this calculator to determine the rotation rate of planets
    http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

    for an object with the same radius as the Earth, the rotation rate required to produce 1 gee of outward acceleration is once every 84.4 minutes
    (0.011847 rotations per minute)
     
  16. Emil Valued Senior Member

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    The ocean surface does not should be equipotential?
    It would be interesting to do a model on the computer.
    I think it would significantly affect the level of the ocean in different regions.
     
  17. eburacum45 Valued Senior Member

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    1,297
    Apparent local gravity is always normal to the surface on an oblate, fast spinning planet.
    The ocean depth would not be affected, although certain geological features such as orogeny might be significantly different in the higher gravity regime at the poles compared to the lower levels of gravity at the equator.

    Because a fast rotating planet would probably experience significant tidal braking, I'd expect earthquakes and other geological activity to be quite common. That might lead to some interesting effects in the ocean such as tsunamis and so on, but it would always find its own level afterwards.
     
  18. wellwisher Banned Banned

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    Actually, although the distances from poles to center is smaller than from equator to center, NASA found another unexpected anomaly. Sound waves travel faster from pole to pole compared to equator to equator when normalized. This means the material from pole to pole is denser. It is not clear if the earth shape and higher density sort of wash.
     
  19. florian Debunking machine Registered Senior Member

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    305
    Fast rotating planets do not necessarily experience significant tidal braking. It could actually be the opposite.
     
  20. Emil Valued Senior Member

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    It would be useful to know what kind of system is the tide system.
    By this I understand:
    If the moon would disappear suddenly, the tide it will still be but smaller and smaller until it disappears or disappear suddenly together with the moon?
    It is an oscillating system or an amortized system?

    Energy needed for an oscillating system is much smaller than for an amortized system.
     
  21. billvon Valued Senior Member

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    Yes - but it does not fall off at the same rate everywhere. On an oblate planet with a equipotential surface (i.e. 1G everywhere) if you go up 1 mile, gravity will be lower near the equator than near the poles. Thus, an ocean will "bulge" along the equator (i.e. be deeper over the equator than over the poles, even if the surface is at perfect equipotential.)
     
  22. cofu Registered Senior Member

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    13
    explanation of the changes of the Earth

    one more variant of the decision of problems which is offered to members of this forum occured on a planet during stages I - IV;
    the Dynamic model - has solved a number of problems which are interconnected also which from a position of Static model of the globe in general are unsoluble-
    to explain changes in the past on a planet have been used: both models of the globe Static and DM, and also the fragmentary information in scientifically technical editions which directly or indirectly concerned changes in the past; as at this forum is impossible to operate with references that DM it w.mammoths.narod.ru
     
  23. Emil Valued Senior Member

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    I think we understand a dynamic system in different ways.
    I understand this: System dynamics
    I am convinced that only a team composed of experts in several fields can produce such a model.

    An interesting thing would be:
    Geometric shape that has the smallest area in a given volume is the sphere.
    If Earth's rotation was greater in the past, and the earth has a more pronounced oval shape.
    By slowing the rotation, the earth is closer to a spherical shape and its surface decreased.
    It can be a cause of formation of mountains?
     

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