TED Talks
Ted: Ted Ed: How Simple Ideas Lead to Scientific Discoveries
Educator, Adam Savage, shares two astounding examples of profound scientific discoveries that came from simple, creative procedures: Eratosthenes' calculation of the Earth's circumference and Hippolyte Fizeau's measurement of the speed...
NASA
Nasa: Imagine the Universe: Speed of Earth's Rotation
Presents an informative answer to the question "What is the speed of the turning of the Earth?"
Cornell University
Cornell University: Astronomy: Eratosthenes
Learn how Greek mathematician Eratosthenes used geometry to estimate the circumference of the Earth.