M1_Lesson 1_How greeks know that earth is spherical.pptx

SCIENCE

1. How the Greeks Knew that the Earth is .. S P H E R I C A L

2. LEARNING COMPETENCY In this lesson, you will be able to explain how the Greeks knew that the Earth is spherical.

3. Have you ever wonder what’s out there?

4. THE MESOPOTAMIANS The Mesopotamians as accounted in their mythology around 6 th century BC described Earth as a flat disk floating in the ocean and bounded by a spherical sky. This idea has prevailed for hundreds of years until a new view was presented. THE MESOPOTAMIANS

5. As the quest for knowledge continues and civilization prospers, several models of the universe were presented. And it is categorized as a geocentric model or Earth-centered and heliocentric model or Sun-centered.

6. THE GEOCENTRIC MODEL In the geocentric model, the Earth was at the center and the rest of the planets and heavenly bodies revolved around it. In all of the geocentric models of the universe, the Earth and other heavenly bodies were assumed to be spheres. They were convinced that the shape of the Earth was not flat instead it was spherical . This idea was already entertained by Pythagoras and Plato however they do not have concrete evidence to support their claim.

7. Until Aristotle (around 320 BC), a student of Plato presented his arguments that established the claim during their time. Aristotle argued that: the sphere is perfectly solid and the heavens are a region of perfection the Earth's component pieces, falling naturally towards the center, would press into a round form in an eclipse of the Moon, the Earth's shadow is always circular thus, if Earth is a flat disc, it would cast an oval shadow even in short travels northwards the Pole Star is higher in the sky.

8. The heliocentric model, the Sun was at the center and the rest of the heavenly bodies including the Earth moved around it. THE HELIOCENTRIC MODEL

9. Another phenomenon considered by Greeks in their claim of Earth's spherical shape was navigation. They observed that when ships sails away, it seems that it gradually disappears behind the horizon.

10. One of the astronomical events that fascinated the early civilization was the eclipse. And the recorded information about eclipses was used by Eratosthenes (about 235 BC) to approximate the circumference of the Earth. This was another proof presented about the spherical shape of the Earth. As you know an eclipse is a shadow formation. This happens when the path of light rays is blocked by an object.

11. What do you think is the Earth’s shape? And why?