JUDGING SIDES IN A CONTROVERSY: THEORY CHOICE AS APPLIED TO EARTH EXPANSION AND SEA FLOOR SPREADING

Thomas Kuhn argued that past controversies are best understood when we can see the facts through the eyes of contemporaries in the debate rather than judging the "wrong" views of the past from the perspective of the "correct" modern view. Hence, it is best if students can read and judge the views of protagonists for themselves. Although "Expanding Earth versus Sea Floor Spreading" was a relatively brief and limited controversy within the mainstream geoscience community, it has the advantage of having primary sources that are accessible to students.

The primary sources that can be used to explore this controversy are: a 1960 paper in which Tuzo Wilson explored the theory of "Earth Expansion" and concluded that "the foregoing hypothesis has the merit of appearing to explain many features of the Earth's surface;" and a 1961 paper by Robert Dietz that takes much the same set of facts and proposes to explain them by spreading of the sea floor. (Note: Hess's version of sea-floor spreading that was published in 1962 first circulated in 1960. However, Dietz's publication is shorter and more accessible.)

What makes Wilson's paper intriguing is his later conversion to tectonics: indeed, Wilson was one of the architects of tectonics.

Students' evaluations of each theory can be framed in terms of the criteria of theory choice: accuracy, internal and external consistency, fertility, unifying power, and simplicity. Framing the controversy in this way can teach students a great deal about the nature of scientific facts and theories, and the criteria used to judge novel ideas in a mature fashion.

While researchers have questioned the value of general "History of Science" courses in communicating the nature of science to students, the approach here incorporates the material on historical controversies into a content-rich physical geology course. When students are then asked to judge other ideas by the same set of criteria, the results are encouraging.