Everything looks great, up to his conclusion that a "continuous uniform change of direction is, of course, a simple harmonic motion." The conclusion is counter-intuitive, as every child knows that there are two kinds of "continuous" motion--running away from your parents in a straight line, or spinning around in the same spot, until you puke. Were you to put on a space suit and head out into the void of deep space, you would be able to throw a baseball in a straight line, or give it a spin an watch it rotate in place. Both motions go on forever... those are the continuous, uniform motions that intuition, and common sense, gives us. There is no way to throw or spin that baseball to make it zigzag back and forth on its own, by itself, forever.9. DBL: Aristotle and his contemporaries insisted that continuity of position is the only condition that can be maintained without the application of some external influence. One of the essential steps toward a theory of motion was a recognition of the tact that a continuous uniform change of position is just as fundamental, and just as permanent, as a continuity of position. The essential feature is the continuity. What is needed now is recognition of the fact that the same considerations apply to direction. A continuous uniform change of direction is just as fundamental, and just as probable a condition, as a continuous direction. A motion with a continuous uniform change of direction is, of course, a simple harmonic motion. There is no more need for anything to sustain a simple harmonic motion than a unidirectional motion.
In the philosophy of yin-yang, the yin is the rotational (feminine) and the yang is the translational (masculine). This is the way RS2 treats motion, as either an angular velocity (yin) or a translational velocity (yang).
Larson, because he concluded that the SHM was a continuous motion, had to use the line formed by a SHM, the photon, to have something to spin, to get rotation (his "rotational base"). Granted, his conclusions are a bit like the old, religious texts where man was created first--linear motion without anything moving--and woman needed a rib--SHM--from man to create the feminine "rotation." So Larson's yin/feminine rotational aspect is the "rotational base," created from the line of translational motion. The RS2 approach is to treat translation and rotation equally as aspects of motion, analogous to treating men and women equally, as two different aspects of humanity.