In response to an earlier post about all posts being boring I would like to pose a question that has been bothering me this last week. I’ve been thinking a lot about black holes but something just doesn’t add up…
On the one hand a black hole is defined as a quantity of matter so dense that not even light can escape. This makes sense, the denser an object of given mass the greater the gravitational force felt at its surface and therefor the greater the escape velocity. It stands to reason that an object may reach a density so great that the escape velocity will be equal to the speed of light. The dense object is completely inside it’s so called event horizon, not even light can escape and the object is quite rightly described as a black hole. Nothing can escape from the black hole so the only clue to its existence is the gravitational attraction felt by nearby objects.
All well and good, so how does a black hole form. Well this makes good sense also. When a star starts to use up all of its Hydrogen fuel the thermal energy it produces can no longer support its mass and the star begins to collapse in on itself under its own gravity. As the gravitation attraction increases atoms themselves are ripped apart to form a thick soup of elementary particles. The stable end state for the collapsing star depends on its size. A smaller star will collapse to form a white Dwarf with a diameter of a few thousand km. At this point the collapse is halted when the ever increasing force of gravity is balanced by the electron degeneracy pressure, an artefact of the Pauli Exclusion Principle which disallows two half-integer spin particles from simultaneously occupying the same quantum state. A larger star will collapse still further; gravity is so great that even electron degeneracy pressure is overcome. Electrons and protons combine to form neutrons and the collapse is only halted by neutron degeneracy pressure. This neutron star has a diameter of only a few km and barely conceivable density of up to 6×1017 kg/m3. If a star is bigger still then it will reach a density where no law of nature can halt its collapse. The star will collapse to a single point, a singularity where the laws of physics no longer apply and crazy things like worm holes may exist; also a black hole.
So back to my question…… Do all black holes contain singularities?
The description above (which may be flawed) seems to suggest 2 separate densities at work. The density of an object from which not even light can escape – a black hole; and the density at which quantum degeneracy pressures can no longer support a body at which point it collapses to form a singularity – also a black hole. So are these 2 densities the same or is it possible to have a super dense object from which light cannot escape that has yet to reach the point of ultimate gravitational collapse. If so why are these 2 densities the same? It seems to be quite a coincidence.
Just to keep things topical I’m also interested in what would happen if I rode my bike into a black hole? Would I be spaghettified or would I ride through a worm hole and discover a new universe?
What wheel size for wormholes?