"Just a theory"

If you want to rile up a scientist, tell them that their understanding of how the world works is “just a theory.”

Remember, in scientific usage a theory is the strongest statement of confidence in explaining the natural world. The most powerful theories tie together apparently unrelated observations.

Evolutionary theory, including the hypothesis of common descent of all living things, is supported by observations as different as paleontological data—the sequence of fossils preserved in the sedimentary rock record; data from biogeography—the modern and fossil distribution of organisms world-wide; data from molecular biology--the close match between human and other primate DNA, data from comparative anatomy—the structural similarities between the skeletal systems of vertebrates from fish to mammals, data from developmental embryology—the discovery of genes common to all vertebrate groups and the role they play in development; among others.

In the sense of having broad support across many different scientific disciplines, evolutionary theory is much more strongly supported than gravitational theory.

Cartoon credit: http://wever.wordpress.com/2008/05/21/

Science & "not-science": telling the difference

The test of whether a proposed explanation is scientific or not is….a test. In the jargon of the scientific method, a proposed explanation must be falsifiable, that is, amenable to being supported or rejected through repeated experiments and retain its explanatory power in the face of new observations or interpretations.

Falsifiability is another way of asking whether an explanation is subject to change. Has the explanation changed with advances in understanding? Science is self-correcting through ongoing testing and re-evaluation.

Secondly, consider the source. Is the explanation from a reliable source? Science is what reputable scientists do. Just as we would not consult an electrician for a toothache, we would not consult religious texts for scientific explanations.

And third, consider, Does the explanation tie together previously seemingly unrelated observations? The best theories do this--Big Bang theory in astronomy, Plate tectonic theory in geology, and Evolutionary theory in biology.

Cartoon is from http://stepsandleaps.files.wordpress.com/2009/08/the-scientific-method.jpg

When a "theory" isn't a theory

Many non-scientists use the words“hypothesis” and “theory” interchangeably (if they use ‘hypothesis” at all) and as synonyms for “idea.”

To a scientist, hypotheses are much more than an idea, much more than an “educated guess”; they are possible explanations based on numerous and repeatable observations (data). In the hierarchy of the scientific method, a theory is an even stronger statement than hypothesis.

The American Association for the Advancement of Science (AAAS), the top scientific society in the United States, defines “theory” as “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. Hypotheses and theories may begin as a bright idea, but they are so much more.

*(http://www.aaas.org/news/press_room/evolution/qanda.shtml accessed 3-25-10)

photo credit: http://www.dreamstime.com/stock-images-dreamstime-download-free-stock-images-and-photos-image1940874

The fact about facts

Scientists do not often speak in terms of “facts” because they live the adage, “the more you know, the more you know you don’t know.” Instead of speaking in simple, declarative sentences scientists are more likely to tag caveats onto their statements along the lines of, “this is the best explanation we have with the data available to us at this time”; a style of communication that both the layperson and the news reporter find highly unsatisfying.

Caveats appended to scientific research tend to get dropped in the translation into seconds-long sound bytes and the popular print and digital media. Even textbooks sacrifice technical detail for grade-level-appropriate content and breadth of coverage.

Compounding the confusion between “facts” and “non-facts” is the discrepancy between the scientists’ use of the words “hypothesis” and “theory”— More next time.

Cartoon credit: thadguy.com

Science & Change

In its day, the pre-Copernican interpretation that the sun and other planets revolved around the Earth was the prevailing theory of planetary motion. The fact that the pre-Copernican explanation is not accepted today points to another fundamental characteristic of scientific theories—they are subject to change. We now know that the Sun, not the Earth, is the center of our solar system, and our modern theories of planetary motion reflect this newer understanding.


The fact that theories change as the result of new information coming to light is evidence of the scientific nature of these earlier explanations. So-called “theories” that do not change in light of new data or understanding are not scientific, are not part of a scientific way of understanding the universe, and are not a part of scientific inquiry.

Photo credit: http://helensguidetothegalaxy.files.wordpress.com/2009/04/001-solar_system-my-fantasy.jpg

When a "theory" isn't a theory

Many non-scientists use the words“hypothesis” and “theory” interchangeably (if they use ‘hypothesis” at all) and as synonyms for “idea.”

To a scientist, hypotheses are much more than an idea, much more than an “educated guess”; they are possible explanations based on numerous and repeatable observations (data). In the hierarchy of the scientific method, a theory is an even stronger statement than hypothesis.

The American Association for the Advancement of Science (AAAS), the top scientific society in the United States, defines “theory” as “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. Hypotheses and theories may begin as a bright idea, but they are so much more.

*(http://www.aaas.org/news/press_room/evolution/qanda.shtml accessed 3-25-10)

photo credit: http://www.dreamstime.com/stock-images-dreamstime-download-free-stock-images-and-photos-image1940874