Chapter X: Expanding Horizons Summary and Analysis

The Earth and Its Neighborhood

In ancient times, the earth was believed to be a flat disc and the universe relatively small - just big enough to surround earth. Aristotle was the first to assert that the earth was a sphere made up of land and water and surrounded by air. There was harsh rejection of his theory. In books published late into the fifteenth century, some 2,000 years after Aristotle, still scoffed at the idea of a round earth. When Magellan sailed around the world, the round-earth theory began to see growing support. Greek scientist Eratosthenes estimated the size of the earth by using the position of the sun and the shadows it cast. His estimates proved to be surprisingly accurate. Parallactic displacement was used to measure the distance of the earth to the moon...