The Scientific Method
Learning Goal: To understand how the scientific method can be used to search for explanations of nature. The scientific method is a procedure used to search for explanations of nature. The scientific method consists of making observations, formulating hypotheses, designing and carrying out experiments, and repeating this cycle. Observations can be either quantitative or qualitative. Quantitative observations are measurements consisting of both numbers and units, such as the observation that ice melts at . In contrast, qualitative observations are observations that do not rely on numbers or units, such as the observation that water is clear. A hypothesis is a tentative explanation of the observations. The hypothesis is not necessarily correct, but it puts the scientist's understanding of the observations into a form that can be tested through experimentation. Experiments are then performed to test the validity of the hypothesis. Experiments are observations preferably made under conditions in which the variable of interest is clearly distinguishable from any others. If the experiment shows that the hypothesis is incorrect, the hypothesis can be modified, and further experiments can be carried out to test the modified hypothesis. This cycle is repeated, continually refining the hypothesis. If a large set of observations follow a reproducible pattern, this pattern can be summarized in a law—a verbal or mathematical generalization of a phenomenon. For example, over the years people observed that every morning the sun rises in the east, and every night the sun sets in the west. These observations can be described in a law stating, "The sun always rises in the east and sets in the west." After a great deal of refinement, a hypothesis can lead to a theory. A theory is an explanation of why something happens. For example, Newton's theory of gravitation explains why objects tend to fall toward the Earth (as well as explaining the interactions between the Earth and the other