That's gravity, not mas. Gravity AT the singularity is supposed to be infinite (though quantum gravity might contradict this, but that theory doesn't work yet), but any sensible measurements will be done at a distance r>0 from the singularity, and there the gravity isn't infinite
Ah, but the gravity isn't infinite, since the object has a finite mass. Pressure is obviously always infinite, since you have infinite density object in a finite density environment.
Hm, how can a singularity form in the first place? As pressure approaches infinity, wouldn't it eventually match the gravity's pull and leave the matter hanging midway between black hole centre and event horizon?
But there is no pressure. The only characteristics the black hole retains of it's parent star, are mass, angular momentum, electric charge.(it's called the No Hair principle)
The collapsing star undergoes a number of steps - the gravity needs to be strong enough to overcome radiation pressure first, which happens when too much of heavy elements accumulated in the stellar core; then there's the electron degenerancy pressure, when atoms are squeezed so close together that the Pauli's exclusion principle(that no two identical fermions, e.g. electrons, protons, neutrons; but not e.g. photons; can occupy the same "spot") acting on free electrons becomes the main factor preventing matter from moving any closer. At this point, the classical gas pressure stops being accountable for.
It should be noted that at this point, one can in fact compress the matter further, but to do so, one needs to move fermions into higher energy states, hence the energy required to compress the mater stems from the energy needed to increase the energy level of the constituent material.
With high enough mass, the electrons in the degenerate matter are so energetic, that they can combine with protons to create neutrons, and the result is a neutron star, where the pressure is provided by Pauli's exclusion principle acting on neutrons. The neutron star is much smaller, as there are no more energetic electrons filling the space between the nuclei and keeping them farther apart. The electron degenerancy pressure dissapears.
Remember however that neutrons also fermions. Thus at this point, one will end up with a sea of neutrons all trying to occupy the same spot but failing because they have the same energy. Again adding energy will shove some neutrons into a higher energy state, but as this increases the density, it decreases the radius of the object. as well as add some pressure because the neutron's trying to get back into it's previous energy state and the other neutrons would need to make place for it. At some point gravity starts scaling faster then pressure and you get a runaway reaction in which presumably the neutrons lose their identity (possibly because they are in such high energy states that they get torn apart or start recombining) and the next stage starts (assuming we don't get quark-degenerate matter in which the quarks are in each other's way preventing further collapse):
If the mass is high enough, the collapse isn't stopped by neutron degenerancy pressure, and the star collapses further, the surface gravity becoming high enough to prevent light from escaping, and we have a black hole.
The point is, once the consecutively appearing "pressures" are overcame, these stop acting any further. Once the last line of defence is broken, there is no more resistance preventing the collapse towards a singularity.
The density of a singularity is infinite, but there is no infinite, or any pressure at all.
I wouldn't claim that so fast. There is no net pressure because gravity scales faster then pressure in this regime, but that doesn't mean the singularity isn't unstable under non-gravitational conditions (probably even the opposite). It should also be noted that for a frame of reference at an infinite distance away, matter forming a black hole will, while collapsing, cause such strong time dilatation effects that it seems to approach the event horizon at an asymptotic rate. At the same time, light coming from the matter will be red-shifted more and more, eventually reaching undetectable frequencies (there are currently no detectors capable of detecting radiation of a frequency of once per millennium for example) and gradually the black hole becomes undetectable. As one approaches the black hole, the frame of reference changes so that one will eventually pass the event horizon from one's own frame of reference. Someone at an infinite distance will however see you approach the black hole asymptoticly just as happened with the constituent matter.[/quote]
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Topic: The human race needs a mega-project. (Read 31474 times)