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My wife found this, and I thought it was pretty easy to understand... Further explanation of a scientific theory In common usage a theory is often viewed as little more than a guess or a hypothesis. But in science and generally in academic usage, a theory is much more than that. A theory is an established paradigm that explains all or much of the data we have and offers valid predictions that can be tested. In science, a theory is never considered fact or infallible, because we can never assume we know all there is to know. Instead, theories remain standing until they are disproven, at which point they are thrown out altogether or modified to fit the additional data. Theories start out with empirical observations such as "sometimes water turns into ice." At some point, there is a need or curiosity to find out why this is, which leads to a theoretical/scientific phase. In scientific theories, this then leads to research, in combination with auxiliary and other hypotheses (see scientific method), which may then eventually lead to a theory. Some scientific theories (such as the theory of gravity) are so widely accepted that they are often seen as laws. This, however, rests on a mistaken assumption of what theories and laws are. Theories and laws are not rungs in a ladder of truth, but different sets of data. A law is a general statement based on observations. Some examples of theories that have been disproved are Lamarckism and the geocentric theory or model of Ptolemy. Sufficient evidence has been described to declare these theories false, as they have no evidence supporting them and better explanations have taken their place. [edit] Characteristics There is sometimes confusion between the scientific use of the word theory and its more informal use as a synonym for "speculation" or "conjecture." In science, a body of descriptions of knowledge is usually only called a theory once it has a firm empirical basis, i.e., it 1. is consistent with pre-existing theory to the extent that the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense, 2. is supported by many strands of evidence rather than a single foundation, ensuring that it probably is a good approximation if not totally correct, 3. has survived many critical real world tests that could have proven it false, 4. makes predictions that might someday be used to disprove the theory, 5. is tentative, correctable and dynamic, in allowing for changes to be made as new data is discovered, rather than asserting certainty, and 6. is the most parsimonious explanation, sparing in proposed entities or explanations, commonly referred to as passing Occam's Razor. This is true of such established theories as special and general relativity, quantum mechanics, plate tectonics, evolution, etc. Theories considered scientific meet at least most, but ideally all, of the above criteria. The fewer which are matched, the less scientific it is; those that meet only several or none at all, cannot be said to be scientific in any meaningful sense of the word. (from wikipedia.com) (free encyclopedia, online) __________________________________ Start your day with Yahoo! - Make it your home page! http://www.yahoo.com/r/hs Enjoy Fall! Rick McGirr Email: [log in to unmask] ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn