Science is a systematic and logical approach to discovering how the universe works. It is not merely a collection of facts, but a process of inquiry that relies on evidence, reason, and testing. Unlike other ways of knowing—such as intuition, tradition, or authority—science demands that ideas be testable and falsifiable. This commitment to evidence and openness to correction is what distinguishes science from dogma.

Science is a way of thinking much more than it is a body of knowledge.
— Carl Sagan

A hypothesis is a specific, testable prediction about the relationship between variables. For a hypothesis to be scientific, it must be falsifiable—meaning it can be proven wrong by evidence. This is a key aspect of Karl Popper's philosophy of science. Scientists formulate hypotheses based on observations or existing theories, then design experiments to test them. If the evidence contradicts the hypothesis, it is revised or discarded.

Controlled experiments are the gold standard for testing hypotheses. In a controlled experiment, researchers manipulate one variable (the independent variable) while keeping all other conditions constant (controlled variables). This allows them to observe the effect on another variable (the dependent variable). Reproducibility is critical: other scientists must be able to repeat the experiment and obtain similar results. Without reproducibility, findings may be unreliable.

Data collected from experiments often contain variability. Statistical analysis helps scientists determine whether observed differences are significant or due to chance. Confidence in findings grows when results are replicated across multiple studies. Peer review, where independent experts evaluate the methodology and conclusions, is another important check. Even then, science acknowledges uncertainty and continues to refine its understanding as new data emerge.

In science, a theory is not a mere guess. It is a well-substantiated explanation of some aspect of the natural world, supported by a large body of evidence. Examples include the theory of evolution and germ theory of disease. Scientific theories can be refined or replaced as new evidence accumulates. This self-correcting nature is a strength, allowing science to move closer to a true understanding of reality.