Objectives

- identify how astronomy started and describe the development of astronomy in different civilizations

- analyze how astronomical observations helped ancient people

- explain the geocentric model of the solar system

- list the discoveries made by some ancient astronomers

The Birth of Astronomy

Ancient people had a clearer view of the sky than we have today.... why???

Observations

Prehistoric people saw what we see in the sky: the sun, the moon, stars, planets. Over time, they charted the movements of these objects.

People used the movement of the Sun and the changing positions of shadows to tell time.

Observations

Eventually, these people began to understand cycles - day and night, the moon, seasons. They built structures (like Stonehenge) to tell when the seasons changed, which helped them plant crops.

Observations

​Early Calendars - Ancient people started designing calendars to track the passing of time. The ancient Egyptians developed their own calendar based on a 365-day year with twelve months and three seasons

Navigation - The stars helped sailors track where they were going. They developed star charts to navigate to other places.

Mythology and Storytelling - People may have gathered at night to watch a learned elder point to stars and patterns in the sky and then tell stories about their gods and heroes. This was natural since the gods were always associated with the heavens, located in the sky.

Astronomy and Astrology

The 12 zodiac constellations lie along the ecliptic and line up month by month with calendars. These 12 were said to have special powers to affect people's lives. This belief is called astrology.

Early astronomers practiced astrology. They were hired by nobles to create maps and charts. The study of the pseudoscience astrology created the foundation for astronomy, transitioning it from a belief to a science.

Mesopotamian Astronomy

These people kept the first astronomical records. They developed the earliest known writing system. Archaeologists have found thousands of clay tablets inscribed with the positions of the planets.

Greek Astronomy

The Greeks made the first globe of the Earth and developed the first model of the universe.

The Geocentric model - a model in which Earth is the center of the universe and is being orbited by the Sun, moon, and planets. The stars are in fixed positions.

Greek Astronomers

Eudoxus - created the first geocentric model of the universe.

Aristotle - made observations that the Earth is a sphere, not flat.

Aristarchus - attempted to measure the distance between the Sun and the Earth (he was way off!) but also proposed the Earth goes around the Sun and calculated the size of the moon

Eratosthenes - measured the circumference of the Earth with impressive accuracy

Ptolemaic Model

Ptolemy "improved" the geocentric model. He studied the motion of the planets. He introduced epicycles,  saying the planets move in small circles while also moving in one big circle.

Great Job!

Today, you learned:

- how astronomy was born

- how astronomical observations helped ancient people

- various astronomical contributions in different civilizations

- some important ancient astronomers and their contributions