The Shape of the Earth

The Shape of the Earth

The shape of planet Earth has fascinated scientists, philosophers and cultures throughout history. For thousands of years man has observed and studied the Earth. Through observations, spiritual beliefs and empirical findings, many theories developed regarding the shape of the Earth.

How has our understanding of the shape of the Earth changed over time?

- Most ancient cultures, such as the Sumerians, Babylonians, even Greece , until the 5th or 6th century B.C., believed that the Earth was flat. (Garwood, 2007, p. 16)

- The Egyptians believed the universe was rectangular-shaped with four pillars that supported a flat ceiling. Egypt was in the center of a flat Earth which was surrounded by water. (Moore, 1968, p. 16)

- Greek philosopher Pythagoras, populated the idea that the Earth must be a sphere back in the 6th century B.C.

- Around 330 B.C. Aristotle accepted the spherical shape of the Earth, observing that the Earth casts a round shadow on the moon.

- Sir Isaac Newton observed the shape of the Earth to be oblate spheroidal or oval shaped, not prolate spheroidal or spherical. (According to Choi, 2007)

- Giovanni Cassini, who discovered four moons of Saturn and estimated the distance between the Earth and Sun to be 87 million miles, maintained that the Earth was flat at the equator. His theory stirred controversy, contradicting Newton's and others who maintained that the Earth was flattened at the poles. (Burns, 2001, p. 55)

What are some discoveries and examples that brought us new knowledge to our understanding of the shape of the Earth?

- In around 200 B.C. Eratosthenes determined the size of the Earth through mathematical calculations and empirical reasoning. "He knew that at summer solstice the sun was directly overhead in Syene (now Aswan, Egypt). On that day, vertical sticks or poles cast no shadows, and sunlight fills the bottom of wells. The town of Alexandria is directly north of Syene (on the same meridian), and on that same day vertical poles do cast shadows, because the sun is then 7.2o from the zenith. Eratosthenes assumed this to be due to the earth's curvature." (According to Simanek, 2006) Eratosthenes reasoned that the Sun's rays are parallel, at the two points he ways examining, because the Sun is very far away. If the Earth was flat, the Sun's rays would be in the same spot at both locations. Eratosthenes calculated the circumference of the Earth to be a little over 24,662 miles. This is remarkably close to our current value of 24,900 miles.

- Ferdinand Magellan was the first noted person to circumnavigate and demonstrate the spheroidal shape of the Earth. The voyage lasted from August 10, 1519-September 6, 1522. "A circumnavigation