Does the Singularity in a Rotating Black Hole Also Rotate?

A spinning point makes no sense. You have to have some extent in order to physically rotate. Now, quantum gravity probably imposes a lower limit on size that isn’t quite a singularity. But even then, physical rotation makes no sense. If the object is at minimum size, there’s no way to track it as it rotates. You’d have to imagine following a point as it moves from place to place. However, it already occupies the smallest possible space, leaving no way to track it.

What spin does do classically is change the topology of the singularity. It becomes like a doughnut. If you approach in the equatorial plane, you fall in. If you approach from any other angle, you can pass through the hole in the middle and back out. These implications pose a fascinating challenge to our understanding of physical rotation and singularity properties.

Can a Singularity Spin?

A question that has puzzled physicists for decades: can a singularity spin? To understand this, we must first clarify that the singularity is not an object made of matter. In reality, a black hole represents a vacuum solution to the relativity equations. No matter is contained within a black hole, but it still carries mass, observable through the curvature of spacetime around it. Angular momentum from the mass that formed the black hole is conserved and invested in the black hole’s spin.

Perhaps this means a superdense ring where the singularity might be, or perhaps there are hidden structures within that singularity. However, the question of knowing for certain remains elusive. The nature of a singularity is inherently mysterious and difficult to investigate.

The Spin of the Black Hole's Singularity

Black holes in reality are not made of physical objects; they are vacuum solutions to general relativity equations. Despite the lack of matter, a black hole’s mass can be observed through the warping of spacetime around it. This mass has angular momentum, which contributes to the black hole’s rotational properties. This angular momentum causes spacetime around a spinning black hole to be dragged, a phenomenon that Einstein's general relativity predicts and that is supported by numerous observations.

Revisiting the singularity itself, in a black hole, there is no dense object in the middle; it is the spacetime itself that is rotating. The singularity, in its essence, is a point where the laws of physics as we know them break down. The concept of spin, in this context, means that the spacetime fabric rotates around this singularity, preserving the conservation of angular momentum.