# Do all black holes spin in the same direction?

My question is as stated above, do all black holes spin the same direction? To my knowledge, the spin in the direction of the spin of the matter that created them. Another similar question was asked here, regarding whether they spin clock-wise or counter clock-wise, and the answer was that it was irrelevant, and dependent upon the position of the looker. My question is more specifically, are all black holes existent, spinning in the same direction? Basis an intuition around, all matter/space/time is expanding outward in a similar fashion from the start point (not a fixed point in space I realize) of the universe. So does that mean that all matter inherently spins around a central axis from which the universe expanded from? In this case, all black holes would seem to be rotating along similar parameters, as all the matter that could create them are spinning as such. However I do not know enough on the details of the universal expansion nor black holes to confirm this.

To end, consider that two black holes are spinning in opposite directions, observed from the position of an observer looking at an xy-plane, one would be spinning from higher to lower numbers on the x axis and the other from lower to high numbers on the x axis, and assume both were at a fixed line on the y axis.

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It's in space. What do you see when you look at it from "underneath"? Now, how do you which side is the "top"? – dmckee Mar 4 '13 at 0:58
I don't think this is a duplicate and it should be reopened. @will: the direction of the spin axis of a black hole will depend on the environment in which it formed, and will be essentially random. This means that for any direction you choose you will get equal numbers of clockwise and counterclockwise spins, but also that you get equal numbers of spins pointing in all directions. For example, a brief glance at any photo showing lots of galaxies will convince you their spin orientation is all over the place. – John Rennie Mar 4 '13 at 6:57
Do all gyroscopes spin in the same direction? – Mike Jun 1 '13 at 22:31
Picture of random galaxy orientations as promised: en.wikipedia.org/wiki/File:Hubble_Ultra_Deep_Field_part_d.jpg – Chris White Jul 1 '13 at 6:18
Question can be stated as follows: Assign a unit vector to each black hole along the axis of rotation, oriented so that the BH spins clockwise when viewed in the direction of this vector. Take any two BHs. The question is then: "is the dot product of their vectors close to 1 (near-equal vectors)? Or (more weakly) generally more likely to be positive than negative? I'd add: Does the likelihood increase if the BH are closer together? If spin directions are random, all answers are "no". – greggo Nov 13 '14 at 5:45

You wrote:

Basis an intuition around, all matter/space/time is expanding outward in a similar fashion from the start point (not a fixed point in space I realize) of the universe.

And then:

So does that mean that all matter inherently spins around a central axis from which the universe expanded from?

But these are contradictory statements. There is no central point or central axis and all matter isn't in orbit / rotating around some fixed center. See this for details.

The spin of one black hole relative to another is completely random (assuming they didn't both form from related source material like the same galactic disk). As @dmckee pointed out, the spin of an isolated black hole is dependent on an arbitrary choice of reference frame so all that matters is the spin of one relative to another. Their spin direction is not correlated in any way.

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+1, but the link you gave is to a WP article about inflation, whereas inflation isn't needed in order to explain this – Ben Crowell Jun 1 '13 at 22:55
@BenCrowell you're right of course. What matters more is that the Universe is homogeneous and isotropic. I (possibly incorrectly) attribute that to rapid inflation but I suppose that isn't strictly required. – Brandon Enright Jun 1 '13 at 23:26

Use conservation of angular momentum here. Angular momentum is a vector quantity, it points along the axis of rotation, so that when you look "along" the momentum vector, the rotation is clockwise from your point of view. Formation of a black hole preserves angular momentum. It doesn't necessarily make sense to talk about the speed of a black hole's rotation, but the momentum, and thus the speed and axis of the rotation, are the same as the star it was formed from (plus the angular momentum of the material that has fallen into the black hole). Since stars generally rotate in different directions, so do black holes.

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The top of the first black holes will be located on the side furthest away from the point of the singularity. Each of which rotate in the same direction. As it feeds a thread of matter, no bigger than a fine thread, emits from its underside. Undectable from our view. The thread then then reaches a point of limitation while the black hole continues to deposit more and more matter to the base of the thread. When the end of the thread reaches maximimun expansion, it bursts emitting gas and matter forming a new galaxy. The new galaxy will rotate in the opposite direction from its parent. This is the connection we observe when we think of the cosmic highway.

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Care to provide any citations promoting this idea? – Kyle Kanos Nov 13 '14 at 3:37