Introduction to Earth Sciences I
1.1 The Earth's Size and Shape, continued
Forward and Inverse Thinking
Relating what Erastosthenes did to the ideas in our opening comments, we would say that the data available to Erathosthenes was the curious observations of shadows in wells and sticks. He then used a theory of angles, to infer one of the Earth's critical parameters - its radius - which he could not measure directly.
Viewed as an inverse problem, the data and theory of angles were used to deduce an important size parameter.
Viewed as a forward problem, the radius parameter and theory can be used to explain the shadow problems.