According to the United States National Academy of Sciences http://en.wikipedia.org/wiki/United_States_National_Academy_of_Sciences
"In everyday language a theory means a hunch or speculation.
Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time.
Some scientific explanations are so well established that no new evidence is likely to alter them
The explanation becomes a scientific theory
Theories also allow scientists to make predictions about as yet unobserved phenomena."
According to the "American Association for the Advancement of Science
A scientific theory is a well-substantiated explanation of some aspect of the natural world,
based on a body of facts that have been
repeatedly confirmed through observation and experiment.
Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory."
It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.
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