Looking for a good Halloween scare? Try this on for size. One day, our galaxy — the Milky Way -- will slam right into the galaxy closest to us, Andromeda. The two galaxies will meld into one, leading to several possible consequences for our Earth. With one of these there will be no significant change for us. Another is that our solar system will be flung out of the combined galaxy and travel off into space on its own. Of course, it’s possible neither of these will happen, and, instead, we’ll be sucked into the huge, mammoth, black hole at the center of the new galaxy.
You see, a bunch of physicists and astronomers have decided the center of virtually every galaxy, including 
ours, contains a black hole. I won’t try and define what a black hole is, Nova tells me even people who study them full time have trouble defining them. However, if you want to learn about them, and why there is a “supermassive” one in the center of the Milky Way, and if, one day, we will be sucked into it (which one scientist believes would be the absolute best way to die), by all means check out Nova’s “Monster of The Milky Way,” airing on Halloween at 8pm ET/PT. It should make for some awfully scary viewing.
Albert Einstein proposed that 
space and time are actually one, that the two form a single “flexible fabric” on which we all sit. The more massive the object, the more the fabric needs to bend in order to accommodate it. A black hole is an object of enough mass that it bends the fabric infinitely.
At least, I think that’s how they explained it. But, if professionals can’t quite define the whole thing, why should I have to? Nova does a spectacular job in this episode of explaining the inexplicable. The computer generated images, while they may not be quite top of the line, look good and do a wonderful job helping make sense of the whole universe (literally).
Article comments
1 - Joan Hunt
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2 - duane
Black holes don't suck much more than normal stars of the same mass. It's only when matter is very close to the event horizon that a black hole really starts to suck.
Nothing much will happen to Earth when our galaxy "slams" into Andromeda. The thing that needs to be appreciated is the vast distances between the stars. The nearest star to Sol is about 24 trillion miles away. It's not like stars from Andromeda are going to be smacking stars from the Milky Way galaxy, like a football scrimmage. Gravity will be king, as usual.
In some ways, all hell will break loose, but on a galactic scale over a very, very long period of time (billions of years). The Sun will find a new orbit and the Earth will follow along, if the Earth is still around, that is. The Sun might melt it by then.
Any way, it sounds like condescending sensationalism for the sake of grabbing viewers who the sponsors don't think are interested in science unless there's some threat on the horizon. It's interesting enough without imposing all the doom and gloom scenarios. Black holes? P'shaw. Nothing to worry about. For a really, really long time.
3 - Tushar Tyagi
The documentary makes me think that probably spiral galaxies are made from spherical galaxies because of the super massive black hole in their center.
As explained in the program, the galaxies would start as normal spherical ones and the black holes jets would create these huge voids in two opposite directions due to there sterilization effect on normal gas and matter. These voids would create a gravitational imbalance in the structure of the spherical galaxy forcing it to collapse into a spiral disc shaped one, with the jets in perfect 90 degree axis of the disc.