Case Study:  HOW COSMOLOGY BECAME A SCIENCE

 The Book of the Cosmos. Imagining the Universe from Heraclitus to Hawking. 

Ch. 8. A Geometrical Argument, Eratosthenes. “’To measure the earth’ defines geometry, and indeed Eratosthenes shows how to calculate the size of the whole earth.”

• What is the difference between a gnomon and a sundial? How is a sundial able to measure time of day, whereas a gnomon cannot?
• How would the ancients measure the distance between Aswan and Alexandria? How would they know that Aswan was almost exactly due south of Alexandria?
• Describe a procedure for obtaining a “ballpark estimate” of some physical quantity that you could not in practice measure directly.
• Suppose you were a common person in ancient times, and you were told that Eratosthenes had measured the size of the earth. Would you believe it? If the procedure were explained in detail to you, would you change your mind?
• If Eratosthenes’ procedure was not an actual measurement of the size of the earth, what use was it? Can you describe a procedure for making a true measurement of the size of the earth?