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Thread: why earth rotates about its own axis?

  1. #1 why earth rotates about its own axis? 
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    the earth rotates around the sun because of the gravitational force between them but why does the earth rotates about its own axis and that too at 23 1/2 degree tilted?


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    The cause of the rotation is closely related to the formation process of the sun and the planets. Have a look at this thread to see, how the solar system began rotating and the planetary system basically formed.

    Now, that disc of planetary orbits was at these times a disc full of gas, dust and pebble like stones that was stirred up by the rotation. Just like the planets nowadays have different orbital periods following Kepler's laws, every single orbit in the early dusty disc had a different velocity. This produced friction leading to eddies and vortices from which according to the current standard theory the planets were formed by accretion and gravitational compression. This rotation is now still present in the rotation of the planets.


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    An original accretion disk causing the formation of the solar system would only cause the Earth to continue to rotate around the Sun and not on it's own axis. All massive things rotate in space from large asteroids to SM BH's. I have an idea that it could be down to gravity in that a mass is falling in an unknown direction towards it's centre but since it is locked in the third dimension, this ends up as a rotation on it's axis.

    As to the 23.5 degrees, that is down to the turbulent formation of the solar system and/or the formation of the Moon.
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    The spinning is sort of like Centrifugal force on a celestial scale
    when the earth was formed it started out as a huge rotating cloud of gas and tiny particles of basic elements, as it clumped together and got smaller, but with the same mass, the rotation increased, think like when an Ice skater in a spin pulls in their arms they spin faster


    The angle is universally decided as a testament to our solar sytems violent past, originally it spin upright and at some point a large, moonish sized object, smashed into the earth, knocking it off balance, the simple answer as to lack of a whopping crater hole is it happened way back, 3.5 billion years ago at least, so the planet was still molten-soft like toffee, so the hole flattened out over the next billion years




    Of course there are plenty of other theories because we can't know for sure, however the above are the commonly accepted reasons
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    Quote Originally Posted by Cyberia
    An original accretion disk causing the formation of the solar system would only cause the Earth to continue to rotate around the Sun and not on it's own axis.
    Sure it can, because it is not a solid disc, but one with differential rotation. This means that two particles on neighbouring orbits have different velocities. Doing this with lots of particles, you create friction between neighbouring orbits. The resulting vortices can be the seeds of the planetesimals that build up the planets. Their combined angular momentum is inherited to the final planet. Another indication that the original disc determines the planet rotation is that (almost) all planets have the same spin orientation. That should not be the case, if the initial angular momenta would have been randomly distributed.

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    So what would cause some of the other planets to spin the opposite direction?
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    Quote Originally Posted by mastmec
    So what would cause some of the other planets to spin the opposite direction?
    I am not an expert in this, so I browsed the net. Here is what I found, and it actually fits to what I imagined in the first place.

    http://imagine.gsfc.nasa.gov/docs/as...s/981026a.html
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