Physics has been in a 'Dark Age' since the 1960s, as many concepts cannot be directly tested.Quantized inertia (QI) re-grounds physics on testable principles and provides a new approach.QI proposes that inertia and gravity are due to the push from gradients in Unruh radiation.QI's grounding makes the theory directly testable and predicts specific phenomena, such as the galaxy rotation cut-off.