What is the difference between a theory and a idea?

Answer 1

An idea is simply a notion, a thought, an explanation that pops into the head. Ideas can be good or bad. In the realm of science, an idea (hopefully good and hopefully logical) is called an hypothesis. Hypotheses are possible explanations for phenomena that need to be tested with experiments (or the gathering of more evidence and data) and need to be 'fitted' with the rest of science fact and theory to see if such a new entry into science makes science a more coherent whole. A hypothesis that is not contradicted by evidence, meets the predictions of an experiment and is useful as a predictor and explainer is promoted to a theory. Darwin's idea of evolution has become a theory by the gathering of fossils and the comparing of anatomy and genomes of many species. Darwin was probably one of the few capable of single-handedly promoting an idea to a theory, given the mountains of evidence he collected. Copernicus' idea of heliocentrism has been confirmed and is now the theory of the structure of the solar system. Rutherford's idea of the structure of atoms has been confirmed and is certainly a theory now - certainly modern atomic sciences would not have advanced this far without it. The Watson-Crick idea of the structure of DNA is a theory these days and was made so by the very experiments of Watson and Crick and Franklin.

Answer 2

A theory is a well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and has been tested and confirmed through observation and experimentation. An idea is a concept or notion formed in the mind that can range from a simple thought to a more complex proposal, but may not have the same level of evidence or testing to support it as a theory. In summary, a theory is a rigorously tested explanation, while an idea is a suggestion or concept that may not yet have the same level of empirical support.