Dear Straight Dope:
The other day, I was watching a movie involving a black hole. Then I caught an episode of The Simpsons involving flushing toilets and the Coriolis effect. Of course, I also read something about the two kinds of black holes (stationary and rotating). I was wondering if there was some galactic force that causes most celestial bodies to rotate in an east to west direction. Since you are all knowing, could you please answer my question. Which way does a black hole rotate?
The first problem here is those words "east" and "west." There’s no east pole on the earth, nor any particular landmark in the universe that we can point to and say, "That way is west." The way they’re defined, in fact, is that east is the direction that the earth is rotating towards, and west is the direction it’s rotating from. If you apply that definition to the cosmos, all celestial objects indeed rotate in the same direction (that is, toward east, away from west). But I get the feeling that’s not the answer you were looking for.
It’s difficult to describe a celestial body’s rotation in words. Even terms like "clockwise" and "counterclockwise" or "right-handed" and "left-handed" depend on your point of view. Suppose you have three gyroscope wheels, one with its axis pointing north-south and spinning counterclockwise as viewed from the north, one with axis pointing east-west and spinning CCW as seen from the east, and one pointing up-down and spinning CCW as seen from above. Which of the three is spinning right-handed, and which is spinning left-handed?
Instead, let’s assume that everything in the universe is screwed–that is, rotating like a screw–and draw an arrow in the direction of rotation. If you take all the bodies in the solar system, and draw arrows for both their rotation and their orbital motion, you’ll find that most of the arrows point in more or less the same direction. Coincidence? Not at all. Everything in the solar system formed from the same cloud of material, and that cloud was spinning in some particular direction, so it’s natural that all of the planets that derived from it would also spin in that direction. However, as we start looking at ever-larger scales, we increasingly see that space is isotropic, which is to say, there’s no particular special direction for anything, including rotation. Things (including black holes) are rotating in every which way, unless you’re on a small enough scale, in which case it depends on where they came from.
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