By converging space and time and presuming both relative to the energy density in the vicinity, and by setting the only "constant" or absolute as not even mass but as light speed in a vacuum, general relativity revealed the natural world's previously unimagined balance and symmetry. Every object is always moving at light speed along a straight line—its equivalent, on a curved surface, called "geodesic" or "worldline"—the one pathway of least resistance like a free fall through 4D spacetime whose geometry "curves" in the vicinity of mass/energy.