Black Holes

I was recently going through my book collection, and have realized all the things that I haven’t read in years, and how my memory of things has grown fuzzy. So, in the spirit of learning (or re-learning, which can be just as gratifying), my next few blogs will be over things from my non-fiction books.

This one will be elaborating on things from Stephen Hawkings’ ‘A Brief History of Time.” (Yes, I know, I am a nerd)

Black Holes
Chapter 6 goes through what is currently known, and what isn’t, about the concept and existence of black holes. The term ‘black hole’ was originally coined in 1969 by John Wheeler, but the concept of a star could have enough mass that its gravitational pull that even light could not escape was first offered by John Mitchell, all the way back in 1783. This is the actual definition of a black hole, it is neither black nor a whole, but simply a body of mass so great, that individual particles of light (theoretically the fastest that anything can physically move) would be sucked into the mass. This means that, if looked at, a black hole would simply look like a black spot in space, because it would emit literally no light, nor allow any light to pass by it for that matter (ignoring some really screwy equations in which the cone of light created by, uh, light, bends around the gravitational pull of the singularity if passing just beyond the event horizon).

For a black hole to form, a star with a mass 30x or greater than the Sun must be formed from a protostellar cloud of gas and dust (a in human biological terms, a protostellar cloud would be a fetus) . When the star starts to run out of full, it begins to cool off, and contract in on itself. From here, there are four forms that the dying star can go into: a brown-dwarf, a white dwarf, a neutron star, or a black hole. (A supernova will generally leave behind a white dwarf or a neutron star, contrary to popular notion that a supernova fully obliterates the star)

The hardest thing that I find to grasp about black holes is how they affect time. According to Einstein’s Theory of Relativity, time is completely relative to everyone’s individual perception. So if a person were falling towards a black hole, he would go on seeing time as we see it normally. But to someone watching the man fall towards the black hole, the closer he got, the slower he would fall, until he reached a point were he would stop falling altogether, at a point known as the event horizon. The hard thing for me to grasp, is that the person falling would have fallen through the event horizon at a certain point, but after he’s past that point, anyone watching him would see him as he was before reaching the event horizon. He would be in two places at once, all depending on who you asked!

A non-rotating black hole is, again theoretically, the only true sphere in the universe. It would have absolutely no marks on it, and would be perfectly spherical. However, since the odds of a star collapsing without moving is vitually zero, black holes should tend to bulge out at the center, like the Earth or the Sun.

There are also primordial black holes, which have existed since right after the Big Bang. After the explosion that created the universe, there were parts of space that held more matter than others, and in places where the matter was highly concentrated, a black hole could form.