What is the speed of rotation of stars close to the center of a galaxy? Is the acceleration close to the center inversely proportional to the square of the distance from the center? Approximately how is the mass distributed across the radius?

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Let's put together the pieces of The Grand Puzzle . (website)

"Let's define another operator, Sz, which we won't pay any attention to."
"This transformation will automatically make zero equal zero."
"It may be true that zero equals zero -- and that is certainly an equality -- but I don't want to go into the details at this time."