$$\require{cancel}$$

# 2: Ancient Astronomy

## Learning Objectives

• Understanding early cosmologies
• How Stone Age structures like Stonehenge were used as ancient astrological calendars.
• Able to describe the astronomical practices of ancient Babylon and Egypt
• Understanding how Greek philosophers and astronomy influenced Western ideas about the universe for centuries.
• Describing the astrological practices in other cultures, including China, Arabia, Africa, and the Americas.

As we noted in Chapter 1, the ancient people took a keen interest in the night sky. They used it as their calendar to tell them when to plant their crops and when to harvest them, when the rainy season was about to begin, when rivers like the Nile would overflow, and when to hold specific religious festivals. They also used it navigation when they took long journeys for trade. People who could predict such important events naturally took on the air of mystery and power. Many closely guarded their secrets, sharing them only with trusted apprentices. These ancient astronomers very often were members of the priest class and wielded considerable influence. After, if you can predict the Nile would overflow, it made sense that you could predict other people. In ancient cultures, astronomy became intertwined with astrology. Even through the middle ages, many astronomers had to draw up astrological charts for their royal patrons in order to have the financing they needed to conduct their astronomical observations. Today, astronomers know that astrology has no legitimate scientific basis. However, that is a relatively recent separation. Astrology and astronomy really only began to part ways during the Copernican Revolution (Chapter 3). Eventually, astronomers like Copernicus and Galileo began to push against this marriage of astronomy and astrology, separating the science from the superstition.

In Chapter 3, we will discuss the birth of modern astronomy through the Copernican Revolution. In this chapter, we will talk about how various ancient cultures made observations about the night sky and how they put that information to use. We know from the structures they built and, in some cases, the records that they left behind, that ancient people took an interest in the movements of those “wandering stars” we call planets today. Often, they built observatories and other stone structures to mark the locations where the planets would appear at certain times of the year. They saw the stars and the planets as things moved by the gods. Until the Greeks, we have little evidence that ancient people had any models explaining the movements of the planets and stars. Their interest lay in knowing when the planets would come out and less in what forces were governing their motions.