To advance a model describing attributes of nature, we are free to claim properties of the model that we believe support those attributes. Absent real experiments we can perform thought experiments to evaluate whether the assumed properties of the model support the attributes we’re attempting to model. At the same time, we must consider alternative models that may also support those attributes. Our model is not validated unless we can invalidate the alternatives. Two models are examined: the familiar Newtonian model of gravity and inertia and the TI field model of gravity and inertia, which is a concept of this author. These two models differ in how matter objects interact with gravity and how each model supports the propagation of nature’s force particles. We look at these two models to determine which supports correctly the time dilation that occurs during four phenomena: the twin paradox, the Global Positioning System (GPS), a clock in free fall in a gravitational field and a clock at rest on the surface of a gravitational body.