1) There are criteria that determine whether a black hole would actually form. Generally if you stuff a lot of hydrogen together at some location, the gravitational force is counteracted by the fusion of the hydrogen nuclei. When this process stops eventually (it depends on what's the final products - it need not all be iron), you don't really have anything to counteract the gravitational force, and you end up getting a star collapse. They do not always end up turning into black holes though - it depends on the mass of the initial star, and its angular momentum. You may end up with dwarfs, neutron stars, or black holes

2) Gravity is an attractive force, and will attract mass. Light, although it has no mass, will also be 'pulled' by gravity [kinda lazy to explain technically why]

3) They tend to be the best candidate objects, but there probably exist galaxies where mega black holes are not the centre of, so no, that's not strictly true

4) You cannot destroy black holes, well at least from what we know now. They do evaporate over time though (I stress that this has not been observed, afaik, but there is strong evidence as to why this evaporation should occur), in a process called Hawking Radiation (which is one of the things that made Stephen Hawking so famous)

5) The black hole, as far as we know, is just a collection of mass, very dense mass. There's something called a no-hair theorem that states black holes have no hair (i.e. no personalities), and all black holes can be described using 3 observables, angular momentum, charge, and mass.

6) Depends. The black hole might have an extremely high momentum relative to Earth, and just gets shot out of the planet relatively quickly, and perhaps the Solar System in due time. If Hawking's prediction is right, then the black hole will evaporate in the LHC, and he'll probably end up with a Physics Nobel Prize. If however, Hawking is wrong, and the black hole stays in the LHC and continues accumulating mass [the black hole in the LHC, if created, will be extremely small, and have quite low gravitational attraction], we're all screwed!

It is quite probable though that it would be possible to eject the black hole out of the Solar System relatively quickly, but frankly the likelihood of a black hole being created and then swallowing us all is bloody bloody small.

This post has been edited by bgeh: Sep 7 2009, 10:15 AM