The principle of vibration. This principle explains that the difference between manifestations of matter, energy, mind and spirit result from varying rates of vibration. This is a compensatory action you might say, to insure a constant momentum in spite of the curvature s influence. Nature also demonstrates that having curvature is the most natural condition. It is enough to establish that the emergence of the photon is the first step in the evolution of the universe, as we know it.
Imaginary energy IS the substance that our mental world is comprised of.
In fact our entire experience is purely mental or imaginary. We know that light waves reflect off our surroundings and then enter through the eye and are passed on as electro-magnetic signals through the optic nerves to the brain. Philosophically speaking we might call these phenomena the Primary Field .