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Thread: Creating a black hole

  1. #1 Creating a black hole 
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    Hello,

    Iím new here, so I will first introduce myself, I am 19 years old and live in Almere in the Netherlands. My English is not perfect but I will do my best.

    A black hole is created when an object has reached a certain density, this is because the gravity of the object overcomes (at a certain point) any force that prevents the matter of witch the object is made of from collapsing into an infinitely small point.

    This counts for every object in the Universe, if you squeeze a banana small enough, it will become a black hole. But there is another way to increase the density of an object; If something is going close to the speed of light, it will get heavier. So my question is, can you make an object implode to a black hole, simply by speeding it up to nearly the speed of light?

    I know that objects also get longer when they approach the speed of light, so this will decrease their density, but I do not know if the density increases more than the length of the object.

    Thanks,

    MacHans


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  3. #2  
    Moderator Moderator Janus's Avatar
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    Accelerating an object up to near light speed will not create a black hole. Any apparent incrase in mass is only measured by in the frame the object is moving relative to. In the frame of the object itself, its mass does not increase. Thus in its own frame, it does not from a black hole. And it it does not form a black hole in its own frame, it can not form a black hole as seen from any other frame.


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  4. #3  
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    Perhaps it would be possible mathematically, but this would require giving the object an infinite momentum. Otherwise the object would not have a point mass, because it's distance is only shortened in one direction so it will still have some finite volume.
    So it is not possible in reality, and as Janus pointed out, the object in question would perceive itself as being at rest, so no amount of length contraction would ever cause this object to collapse. At best it could create a "relativistic black hole" but as I said, this would require an infinite relativistic momentum (impossible).

    Also, you seemed to be confused about length contraction. Distances are shortened, NOT lengthened.
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  5. #4  
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    Quote Originally Posted by Janus
    Accelerating an object up to near light speed will not create a black hole. Any apparent incrase in mass is only measured by in the frame the object is moving relative to. In the frame of the object itself, its mass does not increase. Thus in its own frame, it does not from a black hole. And it it does not form a black hole in its own frame, it can not form a black hole as seen from any other frame.
    Allright I get it
    Very logical, if the mass of the object would change in it's on frame, you would get problems. It would for example mean that I could not lift a banana if I was travelling at almost the speed of light :P
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  6. #5  
    Forum Masters Degree Numsgil's Avatar
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    From what I understand the mas increase from accelerating close to the speed of light is inertial mass, and not gravitational mass. In our common world, the two are the same (how hard it is to push something and how much it warps space are the same quantity), but when you are in a relativistic frame, the two masses diverge. The inertial mass increases, but its gravitational mass does not. It still warps space the same as if it were stationary.

    I could be way wrong, though. So seek a second opinion.
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