Scientists formulate and test their explanations of nature using
observation, experiments, and theoretical and mathematical
models. Although all scientific ideas are tentative and subject
to change and improvement in principle, for most major ideas
in science, there is much experimental and observational confirmation. Those ideas are not likely to change greatly in the
future. Scientists do and have changed their ideas about nature
when they encounter new experimental evidence that does not
match their existing explanations. (NSES, 1996, p. 171)