Scientific Theory and Scientific Laws

Scientific method Process used by scientists to solve problems

Theory In everyday usage, “theory” often refers to a hunch or a speculation. When people say, “I have a theory about why that happened,” they are often drawing a conclusion based on partial or inconclusive evidence. Scientists have hunches, too, but they call them hypotheses, which are the starting point of all good science.

Scientific theory A scientific definition of theory is quite different from the everyday meaning of the word. A scientific theory refers to a comprehensive explanation of some aspect of nature that unifies a vast body of reliable knowledge. In other words, a theory is born when a substantial number of hypotheses point to the same conclusion

A simple example of a scientific theory is the Heliocentric Theory which states that the sun is the center of our solar system. Another example would be Cell Theory which states that all living things are composed of cells. Few people would refer to either of these theories as “hunches.” More likely, in everyday language, these theories would be called scientific facts. In science, a Theory: Explains a natural phenomenon. Predicts future occurrences or observations of the same kind. Can be tested through experiment or otherwise verified through empirical observation. Is Supported by a vast body of reliable knowledge.

Reliance on theory is critical to every branch of science Reliance on theory is critical to every branch of science. Many scientific theories are so well established that no new evidence is likely to alter them substantially. We all accept that… the Earth orbits the Sun (heliocentric theory), living things are made of cells (cell theory), matter is composed of atoms (atomic theory), and the Earth's surface is divided into solid plates that move over geological time (theory of plate tectonics). Each theory has been barraged with scientific tests and still stands intact.

Scientific Law Contrary to common understanding, scientific theories do not “graduate” to laws… Scientific laws are typically short, mathematical expressions representing how nature will behave under certain conditions. Most theories contain laws, and more importantly, they explain why laws work and what they mean.

Scientific method Process that people use to solve problems Controlled experiment only involves one variable Control group- is used sometimes and it is used for comparison. Experimental group Red and blue groups Ex. Three corn plants used. One is placed in red light, one in blue light, and one is placed in white light. They are observed for two weeks and their growth is recorded.

Scientific method Independent variables The variable in the experiment that you control Dependent variable- the result of the independent variable.

1. Scientists are testing a new drug on 6 patients to see how it effects the growth of breast cancer. Identify how you would do control group, experimental group. Also, identify the independent and dependent variables.