Scientific knowledge is based upon observation, and it is supplemented by experimentation. Scientific research follows the scientific method, a four-step process that guides scientists in the accumulation of knowledge.
The four steps of the scientific method are observation of a phenomenon, formulation of a hypothesis, prediction of future outcomes or other phenomena, and experimentation to test the validity of the predictions. A hypothesis becomes a theory or law of nature if the experiments confirm its validity. Otherwise, it must be modified or rejected and the data further examined. Scientists postulate that the basic laws of the universe are unchangeable, and through observation and experimentation, humans determine the validity of their beliefs to better understand the nature of reality.