Thursday, 30 September 2010

For my better understanding (and perhaps yours) - Black Holes, Revisited

I ended my last post with a question - what happens on the 'other end' of a black hole? Well, I don't really know how a black hole is created or how a black hole 'works'. Consider the below a research essay.

Almost every element in our universe above hydrogen was created by nuclear fusion, or the fusion of lighter atoms into a heavier ones.

For nuclear fusion to occur, two (or more) atoms must be compressed together with a force stronger than their respective polarity charges - think trying to force two positively-charged magnets together - so that their nuclei will touch and thus merge. If the binding energy needed for the new heavier atom is less than that needed for the two lighter atoms combined, excess energy, neutrons and electrons are released (explosion), but if the binding energy needed for the resulting larger atom is more, the new atom actually absorbs energy.

Creating nuclear fusion in our environment is extremely difficult: we lack a natural gravitational force strong enough to complete the task, and it takes extreme amounts of energy to force two atoms close enough to fuse (through extreme magnetic forces, particle acceleration, or through heating a plasma enough that its atoms grow agitated enough to collide). On the other hand, stars do all the work themselves.

Stars, the origin of most black holes, produce their energy through fusing hydrogen atoms (our lightest element) into helium. Fusion is attained through both the enormous gravitational compression and heat at the sun's core. Since the binding force and electrons needed for a helium atom (most commonly two neutrons, two protons, two electrons) is less than four hydrogen atoms (one proton, one electron each), energy is released. The helium produced progresses into and becomes the star's core.

Fusion between all atoms in the periodical table lighter than iron create the outward-pushing energy the star needs to counter the enormous inward-pushing core-crushing forces of its own gravity. Fusion between elements heavier than iron needs energy, an energy that can come only from the still-fusable layers above the star's core. So if the star's fusion cycle progresses enough that its core becomes iron, it will collapse.

Here's where the fun begins: since the star's mass, if it is great enough, can only incite a energy-eating fusion at its iron core, here begins a chain-reaction process (that I won't get into here) that will 'compact' the atoms at the star's core into an intensely dense mass of neutrons (that some think resembles the consistence of atom's nucleus - no further compression possible), generating a minor exposion of outward-going nuclear debris that, when mingling with the star's still-fusionable outer layers, will generate a secondary much larger explosion, or supernova (creating an energy that is great enough to generate atoms heavier than iron, in a process called 'r-process'), an explosion that will blow the heavier elements it generates away into the rest of the galaxy. All that remains of the supernova is an immensely compact sphere of unstructured neutron(-proton) core encased by other 'lighter' unstructured atomic elements (progressively: neutrons, electrons, and some ions).

So here we have an object with a huge gravitational pull, no energy and no atomic structure. What this object is called depends on its (former) size: if it was created from an average-sized star, it would be called a neutron star (a non-glowing body that has gravitational pull enough to bend light travelling through its gravitational pull), yet if it had even more mass, it would have a gravitational pull so great that even light could not escape it: this would be a black hole. There is even a hypothesis that, if the star was even larger, it would collapse into a mass so compact that even its core neutrons disintegrate into core of quark-gluon plasma. In any case, the result is a body with gravitational and kinetic constants, a body that can only affect/be affected by the gravity/mass of its neighbours. Black holes do not have a 'sucking power' that stretches to infinite distances; black holes can only affect objects within the limits of their gravitational pull, just like any other celestial body.

If it were up to me, I would tend to group all the above celestial phenomenæ into the same category.

What did I retain from all this? I find it very interesting that our universe's first atoms were hydrogen atoms - all heavier elements are a result of mass accumulation then nuclear fusion. I did learn that a gravity generated by a mass large enough can overcome even the atomic structures of the mass itself. I also think that a bit much is being made about a black hole's 'event horizon': gravity sucks, even light, alright - who cares what 'we see' as 'observers'?
Concerning my quest for a 'constant theory', I can retain that the universe at its most energetic was hydrogen atoms, and that the universe at its energy-eating deadest is black holes, and that gravity, a constant throughout, exists in/affects every known element in our universe. Yes, gravity can bend, or even trap, light... or does gravity bend/trap the beam along which light is travelling? But I digress into my theorising.