Could the earth stop spinning one day??

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Vega, Jul 14, 2006.

  1. sniffy Banned Banned

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    Arse surely?
     
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  3. Ophiolite Valued Senior Member

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    Without any homophobic or homophilic implications whatsoever, I have always preferred the American ass to the British arse.
     
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  5. MetaKron Registered Senior Member

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    5,502
    Well, whatever, but we have some examples that we have direct experience with that make the heating theory bogus.

    We can accelerate small objects at thousands of gees in a centrifuge. If the heating theory held true, the water in test tubes in a centrifuge would boil away before they got anywhere near speed. No object is heated by the act of accelerating or decelerating it. Compression works very poorly for heating solids and liquids, especially a steady pressure against them. Those forms of matter simply compress, every slightly, emitting an infinitesimal amount of energy, then cease to change in temperature if the pressure is constant.
     
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  7. Laika Space Bitch Registered Senior Member

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    The heat would arise from tidal effects, not pure acceleration.
     
  8. MetaKron Registered Senior Member

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    That's even worse, Laika. Tidal effects are when large masses move at a fraction of a gee of acceleration. We can't make a four ounce lump of lead get hot with a single smash from an eight pound sledge-hammer and he's talking about making it hot by tapping it gently with a rubber mallet. The mechanism isn't there to make the mass get hot.
     
  9. superluminal . Registered Senior Member

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    MetaKron,

    You've said:

    My question is, how would you know? We've all presented math and solid physics that demonstrate that the earth would be stripped, boiled, melted and otherwise torn apart by stopping it within a day, by any known mechanism.

    You are not understanding the mechanism of heating in this scenario. It is ancient physics that demonstrates how dissipating energy by slowing something - no matter how you do it - generates heat. You either grab the earth in giant clamps or you "grab" it with a gravitational mass millions of times larger than the earth (since you would need that much gravity to tidally slow it that fast) and you will end up melting the earth.

    You are also not comprehending the magnitude of the forces and energies involved here.

    We present arguments and all you seem to say is "Well, that dosen't prove anything". Well, yes it does.

    Are you finding these discussions helpful in your research? I can't imagine why. You don't seem to learn anything from them.

    Can you show us any way to slow the earth without dealing with dissipating the roughly 10<sup>29</sup> J of rotational kinetic energy of the earth? If you're going to argue this from a technical standpoint, that's the first thing you have to deal with.
     
  10. superluminal . Registered Senior Member

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    10,717
    Correct.
     
  11. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Well said (written), superluminal.
     
  12. MetaKron Registered Senior Member

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    It's just too simple, Superluminal. The tidal forces work like compression waves travelling through the body of the planet. There is some energy spent in collisions between molecules, but the bulk of the energy simply pushes mass. You don't get a significant heating effect with much harder pushes and that's easily proven using a centrifuge or other experiments.

    The energy that you are talking about is expended accelerating mass. It only came up because we were talking about accelerating a mass.
     
  13. Janus58 Valued Senior Member

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    But the motor that spins that centrifuge does warm up considerably as does the brake that eventually slows the centrifuge back down. This is where your example falls apart when it comes to the tidal slowing on the Earth, because in this case the Earth is both the object being slowed and acts as the brake drum.

    The moon's tidal forces do not directly slow the Earth's rotation. they do so through the friction between the tidal bulge and the rotating Earth. If the Earth were perfectly rigid and had no oceans the tidal force of the moon would have no effect on the Earth's rotation because there would be no tidal bulge to act on. On the other hand, if the Earth wasn't rigid but was made up of frictionless materials, the moon's tidal forces still would have no no effect on the Earth's rotation, because without the frictional interaction between the tidal bulge and the Earth the tidal bulge will not be dragged forward along with the Earth and there will be no "backward" tug on the Earth to slow it down.

    It is only through the friction between the tidal bulge and the Earth that the Earth is able to give up its rotational energy. As the Earth turns the relative to the tidal bulge, different sections of the Earth's crust bulges, and then unbulges. The Earth's crust is continually being flexed and unflexed. All this bending back and forth generates heat.

    While it is the whole Earth that is doing all this flexing, it is in the crust where the majority of the heating will take place, for the very reason that it is stiffer. (Try bending a piece of plastic back and forth, it will get warm. Now try bending piece of soft rubber back and forth the same amount, it will get no where near as warm. )

    A perfect example of such heating through tidal action is the Jupiter moon Io. It is volcanically active, yet is small enough that it should have lost its internal heat long ago (like other bodies its size in the Solar system) But because The tidal interaction between it, Jupiter, Europa and Ganymede, it is heated to a point were its interior is molten.
    ( The mechanism works like this: Io is tidally locked to Jupiter, but as the other two moons pass by it they add their own tug which causes Io to wobble. This wobble means that the tidal bulge caused by Jupiter shifts slightly with respect to the moon, causing small section of the crust to alternately flex. Due to the strength of Jupiter's tidal force on Io, this flexing generates enough heat keep Io's interior molten, )

    How much heating you get depends on how much you compress it and how fast. That beside, we are not talking about a constant compression here, We are talking about a body swooping in, genrating enough tidal force to distort the Earth enough for the tidal bulge friction to be large enough to stop the Earth's rotation in 24 hrs or less. This is a lot of sudden active flexing of the Earth, and this will generate copious amounts of heat, no matter how you cut it.

    If you apply the brakes of your car lightly over a long period of time, they will barely warm up because they can get rid that heat almost as fast. You hit your brakes hard over a short period to stop from the same speed and they will get hot. This is the analogy that applies to the Earth's slowing through tidal action, not your water in a centrifuge.

    And on top of all that, the amount of tidal force needed to create a tidal bulge large enough to generate the braking needed to stop the Earth in such a short period far exceeds that needed to remove the world's oceans and air, (and probably exceeds that needed to tear the planet itself apart. )
     
  14. MetaKron Registered Senior Member

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    5,502
    Your mechanism for heating is a fantastic claim that needs to be proven. You are trying to prove a negative here by using physical principles that are established, so yes you need to be able to prove your point to prove that the Earth could not have been subjected to those tidal forces.
     
  15. superluminal . Registered Senior Member

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    10,717
    Feel free to check my calcs.

    We know the earth's rotational kinetic energy is 10<sup>29</sup> J. The earth slows at a rate of about 17us per year due to tidal drag from the moon.

    Rotational kinetic energy of the earth is E<sub>r</sub> = 1/2 I ω<sup>2</sup>

    where:

    ω = 7.27 × 10<sup>-5</sup> radians/second.
    I = 8x10<sup>37</sup> kg m<sup>2</sup>

    The fraction of rotational energy dissipated from this lunar slowdown is:

    (17x10<sup>-6</sup> sec/yr) / (31536000 sec/yr) = 5.39x10<sup>-13</sup>

    So the change in energy due to this slowing is:

    &Delta;E<sub>r</sub> = 1/2 I &Delta;ω<sup>2</sup>

    &Delta;E<sub>r</sub> = 1/2 8x10<sup>37</sup> kg m<sup>2</sup> x (7.27 × 10<sup>-5</sup> x 5.39x10<sup>-13</sup>)<sup>2</sup>

    = 61412 J /yr

    This is indeed negligible (something like the energy of a candle spread throughout the earth and over a years time). The point is that this energy is real, and is dissipated as heat. Look it up. If you stop the earth in a day - gravitationally or with giant clamps - you will dissipate some significant portion of 10<sup>29</sup> J and melt the earth.

    Anyone care to discuss this? How much energy is transferred as angular momentum?
     
  16. Janus58 Valued Senior Member

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    1,794

    Fanastic by what standards? Yours? By them it may well seem so considering that all your arguments consist of arm waving or don't deal with the issue at hand (like your water in a centrifuge argument, which completely mis-represented the mechanisms involved - Really, how lame was that?)

    The arguments I presented are based on nothing more then accepted physics and are back not only by theory but by the very real life example I gave (the moon Io,) which exhibits the very same heating mechanism.

    It's pretty straight forward. We know how much tidal force the moon applies to the Earth. We know how fast the Earth is slowing due to that interaction, therefore we know how fast the Earth loses rotational energy. We know how fast the moon is receding, thus we know how fast the moon is gaining energy. When we compare the two, the Earth is only giving less than 1/10 of its energy to the moon. The rest of the energy has to go somewhere and it goes into heating the Earth. If you slow the Earth at a greater rate, you heat it faster. By knowing how much faster you slow it, you can tell how much you will heat it.

    There is nothing "fantastic" about it.
     
  17. MetaKron Registered Senior Member

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    You haven't proven that the energy is dissipated as heat. The mechanism for transfer of momentum doesn't require that any energy be turned into heat.
     
  18. superluminal . Registered Senior Member

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    And therefore, 9/10 of the 10<sup>29</sup> J (given a moon-sized body) would be dissipated as heat.

    MetaKron, I still don't understand the mechanism you are proposing for the transfer of ALL of the earths angular momentum to some body in less than one day, and the subsequent return of this angular momentum 24hrs later.
     
  19. MetaKron Registered Senior Member

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    We don't have enough to be sure that it's one way or the other.
     
  20. Laika Space Bitch Registered Senior Member

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    MetaKron,

    After you have discussed the mechanism by which the angular momentum is lost and restored, and the lack of tidal heating, I would love it if you could address my questions.
    Where are the erosional and depositional structures that formed from the inundation?
    What is the evidence for your claim that Lake Titicaca was at sea level 10,000 years ago?
    Where is the evidence that mammoths were subjected to violent transport?

    And from a previous post of mine that now pertains to this thread too:

    Metakron, you seem to be suggesting two different things: (a) that Jupiter ejected a long and diffuse stream of debris and (b) that Jupiter ejected a single mass concentration with a comet-like tail. You seem to want (a) to support your (mistaken, in my opinion) claim that components of an unconsolidated arc of material will achieve circular orbits relatively quickly. But you seem to need (b) to be true because otherwise Jupiter would have scattered proto-Venus across the solar system.

    If you believe (a), how did the inner planets escape catastrophic bombardment?

    If you believe (b), how did the planet's orbit become circular over a few thousand years? (This question actually applies to both cases, but you seem satisfied to believe that the orbital motions of the planets and of each fragment in case (b) conspired perfectly to produce Venus's present orbit.)

    How might you explain the incredible rate at which Venus's interior stratified and its surface cooled?

    Why is there so little water and nitrogen in Venus's atmosphere if outgassing occurred so recently/is ongoing?
     
  21. Ophiolite Valued Senior Member

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    9,232
    Laika, all of your questions are pertinent to the issue. Indeed they bracket it rather well. I would recommend one simplification, collapsing your several questions to a single query: Metakron, why did you never bother to get an education?
     
  22. MetaKron Registered Senior Member

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    Why did I bother? I have more things to do with my mind than becoming an overeducated technician who spends his time looking at thousands of samples and interpreting readouts according to the criteria set by someone else.

    Would Jupiter have scattered proto-Venus around the solar system? Of course some of the materials would have scattered. The two ideas that Laika says are contradictory are not contradictory. A stream of mixed elements (or the same element) is attracted to itself and will attempt to form a spherical shape by gravitation. It will also begin to rotate as pieces fall in. It will have a kind of atmosphere until the gases are drawn to the center of gravity. Friction with that atmosphere will accelerate the infall. It starts out as a stream and becomes a blob.

    In other words, the ends of the "comet" will be attracted to each other. They will fall inwards. We won't be able to see that much of the process because the solar wind will make a tail of diffuse gases much larger than the bulk of the materal. The tail is far more diffuse but is bright enough to obscure anything that might be seen by the naked eye. So the more or less diffuse stream becomes a single mass with a comet-like tail. Some gasses will scatter. Some smaller objects won't come out of the gun barrel quite as straight as the rest and those will scatter. Still, the reach of the gravitation of the mass is pretty wide.

    I am not at all sure that Venus's interior stratified or that its surface cooled. I have read about the way that Mariner's figures had to be fudged to make it look like Venus is heated from without rather than within, a direct contradition to the fact that Venus is shrouded by highly reflective clouds that make a much better nuclear winter scenario than a runaway greenhouse effect.
     
  23. superluminal . Registered Senior Member

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    Wow. That's really a shame MK. You somehow got the idea that scientists and engineers are data processing automata, and let that color your decision/non-decision regarding education. You may not like this, but I feel sorry for you. I really do. I can only hope you change your mind some day and realize just how much you're limiting yourself. Without at least some technical background, your ideas will remain insubstantial fantasies. Too bad.
     

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