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Earth's Shape

People have known that Earth is round for millennia; Earth is divided into hemispheres.

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How Did They Do Science?

How Did They Do Science?

Credit: Robert Lopez
Source: CK-12 Foundation
License: CC BY-NC 3.0

Today’s scientists have big toys: space rovers, deep-sea submersibles, electron microscopes, and lots and lots of others. But scientific studies began millennia ago. Many scientific questions can be answered with curiosity and a bit of smarts.

Amazing But True!

In "Earth Was Never Flat!", another Earth Science Real World Application, you learned that figuring out that we live on a sphere was not that hard. Much harder is figuring out the circumference of that sphere. Yet, Eratosthenes, who lived a couple of centuries BC calculated Earth’s circumference. Amazingly, he did it to within 1% of the actual number. In 1849, Hippolyte Fizeau calculated the speed of light. His calculation was within 2%. Neither of these men had advanced tools. Each of them asked a question and designed an experiment to answer it.

Credit: U.S. NOAA. Original uploader was The Anome at en.wikipedia derivative work: Gregors
Source: http://en.wikipedia.org/wiki/File:Eratosthenes%27_method_for_determining_the_size_of_the_Earth.svg
License: CC BY-NC 3.0

Eratosthenes' calculations of the size of the Earth [Figure2]

Can You Apply It?

With the links below, learn more about how these two scientists made their discoveries with such simple tools. Then answer the following questions.

  1. What was the question that Eratosthenes was trying to answer?
  2. What did the letter Eratosthenes received say? Why didn’t Eratosthenes just throw the letter away?
  3. What data did Eratosthenes need to determine the answer to his question?
  4. What was the question that Fizeau was trying to answer?
  5. What data did Fizeau need to answer this question?
  6. According to the speaker, how were these scientists different from other people?

Image Attributions

  1. [1]^ Credit: Robert Lopez; Source: CK-12 Foundation; License: CC BY-NC 3.0
  2. [2]^ Credit: U.S. NOAA. Original uploader was The Anome at en.wikipedia derivative work: Gregors; Source: http://en.wikipedia.org/wiki/File:Eratosthenes%27_method_for_determining_the_size_of_the_Earth.svg; License: CC BY-NC 3.0

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