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Thread: Black Holes

  1. #1 Black Holes 
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    Doe's someone know how can it be that black holes have a uniqe state , in which the laws of physics don't exist at their core?


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    The animation that you have linked to has some mistakes and inaccuracies. So, don't believe everything that is said there. But yes, one possible final stage of a very massive star (not only 3 times the sun) could be a black hole. The main peculiarity of a black hole is that it produces so much gravity that not even light can escape from inside the event horizon. This has some implications coming from the theory of relativity (universality of speed of light, time, etc.). If one assumes an infinite density (which is not necessarily the case) the laws of nature collapse. Infinity is not a good number to calculate with.


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    A neutron star can have an escape velocity of 2/3 light speed. Neutrons are large particles made of protons and electrons.

    A black hole only has 50% more gravity, so to speak, where the escape velocity is now light speed or higher. Of course, neutrons have broken down. Even protons will have broken down, to quarks. However, quarks and electrons are fundamental particles and there is no reason to believe that these can be broken down any further.

    Singularities, as in one dimensional point sources are nonsense. They do not spin, having no dimensions, so cannot cause a black hole to spin (they do, upto nearly light speed in large ones). It is more likely that black holes have spherical cores of electrons, quarks and other fundamental particles at their centre.

    The laws of physics stay. Without them, anything could happen.
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    Moderator Moderator Dishmaster's Avatar
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    Quote Originally Posted by Cyberia
    Singularities, as in one dimensional point sources are nonsense. They do not spin, having no dimensions, so cannot cause a black hole to spin (they do, upto nearly light speed in large ones).
    The problem is that a physical force is needed to prevent forming a singularity. In stars it is the radiation pressure from fusion in the stellar core. In white dwarves it is the degenerated electron gas that counter forces the gravity. Then you have the nuclear forces in neutron stars that balance the gravity. All these stages represent an increasing amount of density, i.e. smaller volume per mass unit. The next denser stage is - for all that we know - a black hole. What could be the force to prevent an infinite collapse caused by gravity? If there is none, you end up in a singularity.

    But that does not mean that every black hole contains a singularity. You just need to put enough mass inside some volume to produce such a gravitational field that the escape velocity is larger than the speed of light. In galactic nuclei, it might be sufficient to have a large amount of stars. For stellar black holes, it is more difficult.

    The picture of describing a neutron as a combination of a proton and an electron is really misleading. Yes, a neutron can decay into a proton, an electron and an anti-neutrino. But that does not mean that a neutron is actually made of these particles. Hence, I would not expect to find a ball of already known particles in the centre of a black hole. I'd rather accept that an entire new kind of matter could be the result of such immense forces. But none can really say.
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    The idea that gravitational pull is always the same in all cases is a fallacy. We have found a black hole of maybe ten solar masses with a stable orbit just 100 miles from it's surface. In a star of that mass, it would almost be in it's centre. I think if anything such as a singularity existed, the most intense gravity would be confined to a very tiny sphere. Certainly not tens of miles. Who knows? A working singularity may even confine gravity inside it so be inert.

    A neutron stays in it's present form with gravity sufficient that 2/3 light speed is needed for an escape velocity. It is even said that neutron stars might have atmospheres a few inches deep made of hydrogen and helium. Why do you think that an electron should collapse with an escape velocity of light speed, which is not that much greater gravity? If they are fundamental particles as is believed, what are they going to collapse into? The mythical strings? New matter is speculation, like the idea of the laws of physics breaking down.

    We have had cosmic rays, single atomic particles hit with the force of a hard thrown cricket ball and they have survived intact. How is a black hole going to break down something that can survive that? They are not magic.
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