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Thread: How long will the Earth continue to rotate?

  1. #1 How long will the Earth continue to rotate? 
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    I was wondering, as I do, how long has the Earth been spinning on it's axis? And how long will it be until it stops doing so? And what will the effects be for the planet and those who inhabit it as it slows to a stop?


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  3. #2 Re: How long will the Earth continue to rotate? 
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    Quote Originally Posted by quantumintel
    I was wondering, as I do, how long has the Earth been spinning on it's axis? And how long will it be until it stops doing so? And what will the effects be for the planet and those who inhabit it as it slows to a stop?
    The Earth has been spinning since its formation some 4.5 billion years ago.

    Presently, the Earth is slowing its rotation due to tidal interaction with the Moon, and in some few billion years will have slowed till it rotates at the same rate as the Moon orbits. (the Moon's orbit is also increasing in size and slowing).

    But before that, Our Sun will enter its next phase of its evolution and expand into a Red giant, possibly even engulfing both the Earth and Moon. Even if the Earth is not engulfed, the oceans will have boiled away and the atmosphere stripped away. So I don't think that the Earth's rate of rotation will be the largest concern for far future inhabitants.


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    Presently, the Earth is slowing its rotation due to tidal interaction with the Moon, and in some few billion years will have slowed till it rotates at the same rate as the Moon orbits. (the Moon's orbit is also increasing in size and slowing).

    Just like to add on.

    Without the moon to slow down Earth's rotation, we will be experiencing 6hs days and 6hs nights. As the moon rotates around the Earth, it exerts its own gravity on Earth that results in tidal bulges caused by the pulling of the Earth's oceans. This is due to a transfer of Earth's rotational momentum to the Moon's orbital momentum as tidal friction slows the Earth's rotation. That increase in the Moon's speed is causing it to slowly recede from Earth (about 4 cm per year), increasing its orbital period and the length of a month as well.

    To explain this better, imagine this analogy. Your riding on a bicycle track along a Merry-Go-Round. As you ride, attach a rope to one of the horses on the Merry-go-Round and you will find that the you will speed up as the horses exert an extra bit of force that pulls you along. Substitute the Merry-Go-Round as Earth, Moon as your bicycle and the rope as gravity.

    Billions of years ago, the Moon was much much closer to Earth. So the tidal bulges were so much greater. Instead of having a 10 ft rise between high tides and low tides, you have an 100 ft rise. As time goes by, we will experience weaker and weaker tides.

    Also, the consequence of such a slowing down on the Earth's part and the speeding up of the orbit of the Moon around the Earth is that eventually the Moon will be perpetually locked to the Earth's rotation (that is one side of the Earth will see the Moon, the other side will never see the Moon again, like Pluto.)

    In response to the originial question on the effects of Earth suddenly ceasing its rotation, we will fly off and be hurled physically off the ground due to inertia, the reluctance of an object to cease its current state of motion, that is, our bodies want the Earth to continue rotating.
    Science is a mountain of theories based on a molehill of facts.
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    Wow, that's amazing, thank you. hopefully humans will have colonised the moons of Jupiter by then...wish I could be there to see it. cheers
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    In response to the originial question on the effects of Earth suddenly ceasing its rotation, we will fly off and be hurled physically off the ground due to inertia, the reluctance of an object to cease its current state of motion, that is, our bodies want the Earth to continue rotating.

    Sorry but the question was of the Earth slowing down gradually due to natural causes and not suddenly. cheers.
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    If earth would slow down, It's becuse it exist a gravity or a adhesion which pulling opposite way, It would take millions or billions years to earth have stopped to rotate around it's axis.

    It's can depend on moons gravity or the suns or the other planets gravitation (I think).

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    Actually there is an interesting point here. If the Earth stopped spinning what would happen? Once we all got to our feet after being thrown what would we find? Gravitational pull wouldn't be affected would it so we wouldn't all go floating off would we? What changes would we notice? What would happen to the atmosphere and weather?
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    Quote Originally Posted by bradford28
    Actually there is an interesting point here. If the Earth stopped spinning what would happen? Once we all got to our feet after being thrown what would we find? Gravitational pull wouldn't be affected would it so we wouldn't all go floating off would we? What changes would we notice? What would happen to the atmosphere and weather?
    If the spinning change, the electromagnetism and centripetal force would be altered causing preasure change on the surface lessening with speed.
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    Quote Originally Posted by bradford28
    Actually there is an interesting point here. If the Earth stopped spinning what would happen? Once we all got to our feet after being thrown what would we find? Gravitational pull wouldn't be affected would it so we wouldn't all go floating off would we? What changes would we notice? What would happen to the atmosphere and weather?
    I think the sunny side of earth will be more desert environment, And on the other ''dark'' side it would be a new ice age. But there should be ''Normal'' environment there the desert and the ice meets together, Or storms.
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    Quote Originally Posted by Cytosine12
    In response to the originial question on the effects of Earth suddenly ceasing its rotation, we will fly off and be hurled physically off the ground...
    Yes an dew to ther conserved momentum... at the equater they woud be movin at about 1000 mph (reletive to earf) as they "fly off"... an interestin enuff... even if a person was standin on the moon at its equator an the moon sudenly stoped rotatin... that person woud prolly jus fall down.!!!
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    Clueless. This isn't Sciforums. Please drop the ignorant bumpkin persona. Use a spell check if you need to. I recommend downloading Firefox and installing one of many spellcheck extensions.
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    Unless someone decides to turn every body of water on the planet into tidal powerstation or the earth gets hit off-center by some very big rocks, the spin is not going to change much before the sun dies.
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    The Earth slows down constantly. A deeper insight can be found here:
    http://eclipse.gsfc.nasa.gov/SEhelp/rotation.html

    Summary result:
    On average, the Earth slows down by about 40 seconds per century.
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    Well, if i'm not mistaken, if the earth stops spinning don't we lose our electromagnetic field? and if thats the case, won't we just fry up and turn into Mars #2 in the solar system?
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    Quote Originally Posted by orion6676
    Well, if i'm not mistaken, if the earth stops spinning don't we lose our electromagnetic field? and if thats the case, won't we just fry up and turn into Mars #2 in the solar system?
    The weakening of the magnetic field may be a possible consequence. The earth won't stop rotating entirely, but probably slow down until it is synchronised with the revolution of the moon.
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  17. #16  
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    Quote Originally Posted by orion6676
    Well, if i'm not mistaken, if the earth stops spinning don't we lose our electromagnetic field? and if thats the case, won't we just fry up and turn into Mars #2 in the solar system?
    It is not the rotation of the Earth that generates the magnetic field, but convection currents in the outer core. Therefore a non-rotating Earth would retain its magnetic field as long as the outer core remained liquid.

    Likely the exact character of it would be different, since the rotation must have some influence on the convection currents and hence the generated field, but these should be small differences. (It occurs to me that the earlier mathematical models of the self generating core dynamo probably ignored the rotation, yet still produced good results.) Dishmaster has implied as much.
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  18. #17  
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    Quote Originally Posted by Ophiolite
    Quote Originally Posted by orion6676
    Well, if i'm not mistaken, if the earth stops spinning don't we lose our electromagnetic field? and if thats the case, won't we just fry up and turn into Mars #2 in the solar system?
    It is not the rotation of the Earth that generates the magnetic field, but convection currents in the outer core. Therefore a non-rotating Earth would retain its magnetic field as long as the outer core remained liquid.

    Likely the exact character of it would be different, since the rotation must have some influence on the convection currents and hence the generated field, but these should be small differences.
    Thank you for the clarification. I just thought that the friction inside the earth would eventually also propagate the reduced momentum to the lower layers. But I guess that the main driver for the convection is the heat source, i.e. natural radioactivity. Any idea on how this heating could be reduced in the far future?
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    Quote Originally Posted by Dishmaster
    I guess that the main driver for the convection is the heat source, i.e. natural radioactivity. Any idea on how this heating could be reduced in the far future?
    The heat in the core is primarily residual heat from formation of the planet i.e. derived from gravitational collapse. The core, being primarily iron and nickel, contains few radioactive elements. These are concentrated in the mantle where the heat generated by their decay contributes to the solid phase convection currents that exist there. The heat of the core also contributes these currents and are likely the more important factor.

    The time for the core to cool and solidify has been calculated many times. Lord Kelvin, before we knew of the mantle/core divisions, calculated an age for the Earth based upon how long it should take the Earth to cool, assuming it began in a molten condition.

    Because he was unaware of radioactivity his figure was too small by one or two orders of magnitude. This was a problem for Darwin's new theory, since there seemed to be insufficient time for complex life to evolve using Kelvin's timescale.

    I believe the current view is that it would take billions of years for the core to solidify completely, but the magnetic field would also likely weaken and perhaps die out altogether before there was full solidifcation.

    Now all of this is rather an oversimplification. I know there are computer model simulations that throw up inconsistencies in the cooling history. Despite what I said earlier some models require a significant radioactive contribution from within the core. There are also 'interesting' things going on at the core mantle boundary that may greatly effect thermal conductance.
    Another controversial view is that there is a self sustaining fission reactor at the heart of the Earth. This is an unpopular idea, since uranium is believed to be lithophilic, being concentrated in crust and mantle. However, it illustrates that our understanding of deep Earth structure is still in a very basic state, arguably equivalent to where we were with plate tectonics three decades ago.
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  20. #19  
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    quote]The weakening of the magnetic field may be a possible consequence. The earth won't stop rotating entirely, but probably slow down until it is synchronised with the revolution of the moon.[/quote]

    When the dinosaurs still walked on earth, It was 370 days on earth on 1 year, And now it is 365 days. So earth maby have slowed down on it rotation around the axis?
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