The primary methodology used to test scientific theories is the scientific method. This structured approach involves several steps: making observations, forming a hypothesis, conducting experiments to collect data, analyzing results, and drawing conclusions. A fundamental aspect of the scientific method is the principle of falsifiability, where hypotheses must be testable and capable of being disproven through evidence. Peer review often follows, ensuring rigorous scrutiny by the scientific community before theories are widely accepted, contributing to the advancement of scientific knowledge.