Bad Astronomy and Universe Today Forum - View Single Post

tdvance · #20 (**permalink**) 13-May-2008, 05:43 PM

It's actually funny to read some of the work done on black holes (e.g. the accounts in Kip Thorne's "Black Holes and Time Warps: Einstein's Outrageous Legacy)--doing exact computations for the general case or even one specific realistic case is just too hard. So, physicists compute a lot of non-realistic cases--e.g. nonrotating, rotating with neutral charge, etc. to get a picture of what is going on--kind of like studying a forest by plucking a random leaf here and there.

I recall some of the more funny images presented by some studies--e.g. of course one computed what happens when a perfectly spherical star collapses into a black hole. But what about real stars with flattening due to rotation, prominences, stars distorted by nearby stars, etc. They are hard cases--so, instead I believe it was Kip himself who computed computed--this is the funny one--the result of a cubical star collapsing into a black hole. (the end result was the black hole would still be spherical, or an oblate spheroid due to rotation). Other computations included, star with a "mountain" on it, etc. Since they all gave the same end result, a plain-old spherical/oblate spheroidal black hole, the conclusion is that probably any real star with less-funny shapes does the same.

Now, I wondered--Robert Foreward, in an appendix to "Dragon's Egg", claimed a torroidal black hole would, among other things, rotate the 4-dimensional spacetime so that time is one of the spatial dimensions, and some other spatial dimension is now time, so you could travel through time by accelerating your spacecraft through it. Now--in light of the above, I figure a torroidal black hole is unstable and collapses very quickly to a sphere--but how would one arise? A super race maybe taking a very long string of black holes, moving them into a huge Kemplerer rosette (would this be "torroidal enough"?) and reducing the radius till they merge.