What do we mean when we use the term equal (as in equal but opposite forces)? We are comparing the difference between less vs. more. For example: Although a vacuum is the opposite of density, both a vacuum or density can motivate work and work simply means movement. When we use the term equal in conjuction with the circumstance of balance (movement) theoretically both opposites could balance into one. If we took all things in the cosmos and balanced them to one entity... that would constitute original space. Movement in a specific direction must cause displacement, and displacement in turn causes resistance. Resistance in turn creates compression (density). What is created (left behind) by this action is a degree of vacuum equal to the cause. The practical application of this is: Repulsion gravity converts original space (the one, common, original source) to attraction gravity* and cosmic evolution begins. So, although it is the same space and the principle is simple, circumstances change. Two that are the same repulse one another and two that are different attract. In the reality of today's attraction gravity cosmos, repulsion gravity and attraction gravity acting on quanta and fields, imparts these qualities to the participants. But, because the quanta and fields are made of the same one, common, original source and the only thing different is their temporary density, they can switch themselves back and forth between the forces depending on circumstance (change in density). What motivates them and indeed all of the cosmos, is an attempt to achieve balance (equal out).

*detailed in the explanation of first movement.