It's widely held that light's velocity is fixed. It remains the same for everyone regardless of relative motion. Many believe Einstein proved this through special relativity's time dilation and length contraction for moving objects. But its relativistic effects only work one-dimensionally in the forward direction of linear motion. In our real nontheoretical world of three actual dimensions, light's perpendicular velocity diverges from its forward velocity while exceeding 186,000mi/s. This glaring, unresolvable contradiction plainly demonstrates the conceptual impossibility of light's constancy. It simply has to compound with the motion of its source and that of other reference frames. This is easy to demonstrate. It's also clearly indicated by all of the Michelson-Morley type experiments and confirmed conclusively by Sagnac's. Moreover, light's velocity is also variable. Its speed changes as it traverses the varying density of a gravity field. Einstein asserts this as well despite the nullifying conflict. But the problems with light's constancy don't stop here. Both its factual compounding and its variability have devastating consequences for relativity. They completely undermine its founding premise, which in turn invalidates all of it, including its general theory as Einstein himself even concedes.