Saturday, January 22, 2011

On Black Holes

A while back I was racking my brain trying to understand the physical volume of a black hole, both alone and in relation to it's event horizon, technically known as a Schwarzschild radius. It dawned on me–or rather the idea finally clicked after hearing it professed many times–that the best way to imagine the thing in one's head is actually not as an object but as an affected region of space-time.

Typically, when a star burns off all its hydrogen it switches to burning heavier elements that have formed as the result of the star's own natural fusion reaction. Fusing helium next results in heavier elements, which sink to the star's denser core, eventually forming up the heaviest, non-fusible material there, carbon. Burning through these lighter elements decreases the star's mass while maintaining more energetic fusion reactions, swelling the thinned outer layers of gas against the weakening pull of gravity.

This is what ultimately kills any star which has yet to go nova or smolder to a charred lump of diamond. Gravity overwhelms  the fusion reaction and collapses the star into itself, throwing off its outer layers as the bounce into each other. Depending on how massive it was to start, the star might collapse enough to ignite the heavier elements mentioned above and gain a few more years, but eventually those run down and there is a full collapse. The atoms smush together so hard and so closely that protons and electrons merge back into neutrons, forming a "neutron star," a diamond-carbon shell over a sea of "liquid" spinning neutrons about 12 miles across.

If the collapse is still ongoing under an even greater mass, it's suspected the star can be further squished into a "quark star," where the neutrons merge back into loose quarks, about 1/3 up- and 2/3 down-quarks but potentially also some "strange" and worse varieties. Beyond that maybe a "prion star" can form if there's something smaller than a quark, but we're getting farther and farther afield of our topic.

At a certain point of mass, the force of collapse within the star overcomes the ability of matter to fit into a finite volume, or rather space breaks because it can no longer fit more mass into less volume. All of the star's mass condenses to a 1-dimensional point.

The trick is, all that mass still affects a region of space exactly the size as the original star, less of course the measure of mass thrown off by the tremendously energetic implosion event. The event horizon, then, can be pictured as the ghost remnant of the original star's surface area. At the surface of the Earth, escape velocity for a rocket to exit gravity's pull would be 11.2 km/s. For the event horizon, it's now greater that the speed of light C. So really, the event horizon is just an arbitrary boundary sphere (or sometimes a donut) in space, while the mass of the black hole itself lies in the center. Outside it's the point at which no light escapes from within and around which some external light bends, but inside you'd get to see all the pretty lights from around you as you were pulled in towards the central singularity point, watching the universe speed up behind you due to relativistic effects as you go through a process scientifically dubbed "spaghettification."

Some times, it's really best to just not ask me what it is I'm thinking about for so long in the shower. Next time just pretend I'm masturbating or something.

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