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Second Black Hole at the Center of the Milky Way
Tsalg pastes "A second black hole lurks at the centre of our Galaxy, according to astronomers who have watched a cluster of stars spinning around it. Just three years ago, astronomers confirmed that the Milky Way revolves around a supermassive black hole, called Sagittarius A*, which is about 2.6 million times more massive than the Sun. But now a much smaller black hole, just 1,300 times our Sun's mass, has been found orbiting about three light years away from its supermassive cousin. placing it intermediate between the relatively small (stellar mass) black holes in the Milky way Galaxy and the supermassive black holes found in the nuclei of galaxies."
just think, we wont get sucked in unless we are actually aiming to do so, otherwise we will just revolve around the black hole. so its nothing to get worried about, and by the time the black holes do collide(if they actually do), it will be many years until the effects are felt here on earth, and by that time we will blow ourselves up.
I thought what I'd do was, I'd pretend I was one of those deaf-mutes. - Catcher in the Rye
And the black hole that they might have in their center?
Density waves don't need to be limited to just inelastic collisions. Look at traffic on a highway, in a traffic jam. You've got density waves there too, and no collisions, hopefully.
In a galaxy, gravity is the binding force. Imagine every star in the galaxy as a physical ball. And for simplicity's sake, imagine that it's connected to all it's neighbors by a spring. That spring is gravity. Now, move the sheet of interconnected stars that you've just made. Bingo, you have density waves.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
Do we have any way of knowing if the universe as a whole is rotating? Or if it is, in what plane and how fast?
One of the key axioms of Cosmology is that of isotropy. No matter which way you look the universe looks roughly the same. This has been a very successful conjecture and many a cosmologist wouldn't like to throw that principle away without a fight.
I'm no expert at cosmology but my immediate thought is that material would spread out along the plane of rotation like dust does with newly forming stars. Therefore we'd expect to see more stars in single plane than elsewhere in the sky.. which isn't true.
Of course, the rotation could just be very slow but I think it's unlikely.
Simon.