# Question from a non-astronomer /non-mathematician regarding rotation speeds

I have been watching too much TV related to black holes. Most black holes are depicted with a disk of matter that spirals into the black hole. Does the mass and diameter of the disk have a bearing on the rotational speed, maximum rotational speed of a black hole? Also, do black holes have gravity? It looks like they must in order to collect matter. Does the gravity of a black hole create gravitational waves much as the electromagnetic waves created around the earth? Do these waves have any influence on the speed of the black hole's rotation. What about if the rotation if the black hole is not symmetric?

• Can you pick a single question for the answers to focus on, which is not covered by other questions here? May 21, 2019 at 3:17

Most black holes are depicted with a disk of matter that spirals into the black hole. Does the mass and diameter of the disk have a bearing on the rotational speed, maximum rotational speed of a black hole?

It's much more the other way round. The size of the accretion disk is determined mainly by the mass of the black hole, and by the supply of new material passing close enough to the black hole to possibly get trapped in the disk. The rotation of the black hole only plays a role in the innermost part of the disk, where the strange effects of General Relativity cause the material of the disk to be dragged around.

Also, do black holes have gravity?

Yes. Indeed they don't really have much else.

Does the gravity of a black hole create gravitational waves much as the electromagnetic waves created around the earth? Do these waves have any influence on the speed of the black hole's rotation. What about if the rotation if the black hole is not symmetric?

A black hole is only asymmetric for very brief periods after large objects fall into it (for example when two black holes merge). In this case it produces very large amounts of gravitational wave energy, rapidly shedding the asymmetry. This process is called "ringdown". A symmetrical spinning object does not radiate gravitational waves.

A very good source for seeing these kinds of things are the videos produced by the SXS consortium with the caveat that they are visualisations of aspects of what is happening, not images. There are far too many dimensions of data to show the whole story.