This was exactly what gave Golden Core cultivators of old such arrogance and confidence to spout lines like, "When my core turns, Heaven's will detours," or, "A mortal stores breath in the lungs; a cultivator stores worlds in his Golden Core."
Unlike us earthlings who had to rely on esteemed Daoist Galileo, cultivators of Firmament Heaven discovered the truth behind celestial bodies long ago on account of being able to fly up to the firmament and see for themselves.
So they recognized that after compressing into a spherical shape, they should make their cores rotate like the sun and the moon to generate their own unique force, ambiently attracting spiritual energy in the air to refine into Dharma Power.
However, getting the core to start spinning was not easy, requiring a lot of focus and effort, as at this stage it was newly born and a little fragile, not to mention it was full of Magic Power that hadn't been converted yet.
