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Thread: 2-D space

  1. #1 2-D space 
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    what will happen if a spherical body of mass m starts rotating at a speed nearly equal to the speed of light?


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  3. #2 Re: 2-D space 
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by parag1973
    what will happen if a spherical body of mass m starts rotating at a speed nearly equal to the speed of light?
    Please explain. Rotation 'speed' is measured in rpm or some such unit. Speed of light is measured as a straight line speed.


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  4. #3 2-D space 
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    consider a top rotating about its axis.if this top starts rotating at the speed of light what will happen(this may seem hypothetical)
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  5. #4  
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    A small body will be torn apart by centrifugal forces long before it approaches even a small fraction of light speed. This is an actual problem in the design and manufacture of the ultracentrifuge.


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  6. #5 Re: 2-D space 
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    Quote Originally Posted by parag1973
    consider a top rotating about its axis.if this top starts rotating at the speed of light what will happen(this may seem hypothetical)
    Which part is at the speed of light? The axis has zero speed.
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  7. #6 2 D 
    Forum Sophomore Vaedrah's Avatar
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    Perhaps parag1973 is considering relativistic effects on a hypothetical body rotating with angular momentum based on its mass and geometry. There is no reason to assume that such a body is made of typical material and could be a black hole for example.

    The outer region of such a body will have a "linear velocity" for a short time period and an acceleration towards the center. Therefore the outer region should experience time dilation compared to inner regions and also mass increase based on ). Could this result in a fundamental limit?

    Further, is there a maximum frequency of rotation? Say we represent the angular rotation frequency as . From Planck, . From Einstein, . The largest mass we know of is that of the universe, let's call this . Given , the maximum universe frequency should require both energies to be equal, i.e.



    i.e.



    (Does Planck's energy prediction apply equally to mechanical bodies as intended for electromagnetic entities?)

    Angular momentum " where represents the moment of inertia for a body. In classical physics I can be predicted for different geometries e.g. a solid sphere has . However this assumes constant density and even if this were true prior to rotation, at high rates the outer regions would increase in mass density due to relativistic effects. So my guess is that we can only answer this question (and the previous question on ratio of to ) if we assume that the universe is collapsed into one single black hole with a moment of inertia "" and a maximum frequency of rotation .

    Then

    If this black hole has an event horizon of radius , I wonder what its moment of inertia "" would be, based on its presumed geometry?

    Being a black hole, it shouldn't fly apart when spun like a top
    "The sky cannot speak of the ocean, the ocean cannot speak of the land, the land cannot speak of the stars, the stars cannot speak of the sky"
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  8. #7  
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    Quote Originally Posted by SteveF
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    A small body will be torn apart by centrifugal forces long before it approaches even a small fraction of light speed. This is an actual problem in the design and manufacture of the ultracentrifuge.


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    I agree.


    Sincerely,


    William McCormick
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  9. #8 2-D space 
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    if in place of the top if we consider an elementary particle to revolve around a point at the speed of light? the conclusion i have drawn from the rotating top is that a 2-d space will actually be created around the diameter of the top.is that posibble. i imagined that as the rotating top approaches speed of light its mass will increase. the space around will be sucked into the center of rotation.
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