Using my first IBM clone I attempted to prove Newton was wrong in his stating there are no net gravitational forces inside a large hollow core spherical body. After realizing my algorithms had described a disk-shaped object, I concluded my hopes of having made a great scientific discovery were without basis. Newton was right.
There are no net gravitational forces at any point inside large hollow core spherical bodies yet unlike spherical bodies there are no net gravitational forces only at the exact gravitational center of any disk-shaped object such as a spiral galaxy. This precludes the existence of a black hole, or any mass, residing at the center of any spiral galaxy.
A spiral galaxy rotates as a pinwheel, not as body consisting of millions of stars orbiting a central mass. Actually, a central mass could not exist at the gravitational center of any disk-shaped object. Should a mass appear at the center it would be pulled outward into the surrounding stars. A spiral galaxy does not require a large amount of dark matter in order to maintain its structure, it is held together by its own gravity. However, a dense field of photons will provide a large amount of mass even though it would be a stretch to call it dark matter.
An object located at right angles to the plane of a galaxy and trapped by the gravitational force of the galaxy would be accelerated to a high speed. It would likely be pulled apart to the molecular level and have a clear passage through the galaxy center only to be jetted out the other side. It would eventually be slowed by the galaxy's gravity, passed back through the center and jetted out the other side. The galaxy center would become an incredibly powerful particle accelerator and collider.
After being told over a lifetime there is a large mass black hole at the center of spiral galaxies, I found it very hard to change my thinking. After I finally realized my algorithm was correct it now seems real to me, there is no central mass in any spiral galaxy.