This web page presents the story of how the "spherical Earth theory" was challenged, tested, defended, and ultimately rejected through rigorous experimentation in the late 17th century. As a result, the theory of the oblate Earth was adopted. The story brings the controversy to life, as it describes the efforts by Christian Huygens to defend the concept of spherical Earth through his pendulum experiments. The established scientific community at the time was reluctant to deviate from the spherical Earth theory, in part because of prevailing belief that a creator would not build an imperfectly shaped Earth. The story goes on to explore pendulum experiments conducted at equatorial French Guiana, where evidence repeatedly showed that the gravitational constant was slightly different at the equator than at Paris -- a contradiction of Huygens' theory.

This resource was developed to help students gain insight into the complexity of testing an established scientific theory, and the need for alternative theories as part of the challenge process. See Related Materials for links to the full collection of "stories" that span five science disciplines.