Scientific theory

A scientific theory is more substantial than a conjecture or hypothesis, but may not be verified as consistent with empirical data.

It is a plausible and consistent explanation for observable phenomena.

To be considered scientific, a theory must be falsifiable. This means that there must be some way to do experiments that could counter the theory's predictions, thus disproving the current theory.

Generally accepted scientific theories have been tested and survived over time, have evolved when appropriate, and modified toward consistency with newly discovered data, have not been shown to be false and can make predictions about natural phenomena. Scientific theories can sometimes be used as the basis for industrial and technical developments.

A scientific theory does not necessarily have to have strong experimental support or accepted by the scientific community. Scientists often refer to untested theories and competing theories. Theories can be extremely well-confirmed, such as conservation of energy, or speculative, such as String Theory.

No scientific theory can be said to be absolutely true, but a successful theory is most consistent with the actual behavior of the universe. When a phenomenon is discovered that is inconsistent with the prevailing theory, the theory is either revised or thrown out entirely. An example of this is Newtonian mechanics--while Newton's 3 laws of motion provide extremely accurate descriptions/predictions of the behavior of medium-sized objects at low speeds, they are inconsistent with the behavior of very large, very fast, or very small objects. Newtonian mechanics has been shown to be a limiting case of general relativity (in the limit where velocity goes to 0) and quantum mechanics (in the limit where Planck's constant goes to 0, essentially the limit of large objects). Usually a theory which is inconsistent with some experimental evidence is not completely falsified; it is instead shown to be a simplified version of a more complete theory.

Common usage

Evolutionists frequently argue that the word "theory" means very different things to scientists and non-scientists. For example, a PBS TV show says:

When we use the word "theory" in everyday life, we usually mean an idea or a guess, but the word has a much different meaning in science. This video examines the vocabulary essential for understanding the nature of science and evolution and illustrates how evolution is a powerful, well-supported scientific explanation for the relatedness of all life.

The American Museum of Natural History exhibit on Darwin says:

In everyday use, the word "theory" often means an untested hunch, or a guess without supporting evidence. But for scientists, a theory has nearly the opposite meaning. A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts.

In science a theory is something that ties together facts. For example, an apple falling to the ground when you let go of it is a fact. From this we can hypothesize that there is some force pulling it down. The set of observations and mathematical formulae that explain how this force works, and the experiments which demonstrate that those observations and formulae are correct is called the Theory of Gravity.