The symbolism of the cross is so profound that we can never hope to understand it fully. One of many interpretations is that it represents a human being, the synthesis of the masculine principle (the spirit and the intellect) and the feminine principle (the soul and the heart).
The union of these two principles produces movement. Yes, the union of feeling and thought gives birth to movement, that is to say to action.
When the cross is set in motion it produces a circle, the sun. And as the movement becomes more intense, the sun becomes more luminous.
The sun unites in itself the two principles; it is the cross in motion.