In ancient times, the movement of the sun, moon and stars and the changes in the universe were crucial to people. The laws of these celestial bodies directly affect people's production activities and daily life, such as the planting and harvesting of crops, the determination of festivals, and even the arrangement of some religious ceremonies. Therefore, ancient people had a high enthusiasm and importance for the observation and exploration of the universe.
Although astronomy in ancient Mesopotamia was extremely developed, its limitations were obvious. Due to the limitations of technology and cognitive ability, the ancient Mesopotamians' understanding of the universe was still stuck on the earth, and they regarded the mountains and the sea as the boundaries of the universe, and believed that the sky was suspended above the mountains. Every day, the sun crosses the sky, then dives into underground tunnels and rises again in the east the next day.
Although the ancient Mesopotamians' cosmology was limited, this does not mean that their understanding of the universe was backward. On the contrary, their study of astronomy has reached a fairly high level. They were able to distinguish between planets and stars, and made precise observations and records of the planets' trajectories. These data show that they have a mastery of less than 1% error in the planetary conjunction period, which shows that they have reached a fairly high level of accuracy in astronomy.
In addition, the people of the ancient two river basins also discovered the zodiac and divided the zodiac into twelve constellations. Each constellation is named after a mythical god or animal, a symbolic system that is still used today, known as the zodiac. The naming and division of these constellations not only reflects the ancient Mesopotamians' in-depth study of astronomy, but also demonstrates their deep understanding of mythology and culture.
In ancient Egypt, people had a deep understanding of the changing of the seasons. In order to better cope with the changes in nature, ancient Egypt had special priests who were responsible for observing celestial phenomena. Not only did they accurately eclipse the sun and moon, but they also developed a unique calendar based on the movement of the constellations.
Among them, the orbit of Sirius attracted great attention from the ancient Egyptians. When this bright star rises just before sunrise and appears on the eastern horizon with the sun, this peculiar sight is called "kaisunrise". After a long period of observation, the ancient Egyptians discovered that the Nile would flood two months after the occurrence of the "Kai Sun Rising". This periodic flooding of the Nile provided the ancient Egyptians with a sign of the changing of the seasons.
Based on observations of Sirius, the ancient Egyptians identified the moment when Sirius rose just before sunrise as the beginning of the year. They named the first four months the flooding season because it was the time when the Nile flooded. The next four months are the recovery period, and the last four months are the dry period, which is also the harvest season.
After thousands of years of continuous observation and summarization, more than 4,000 BC, the ancient Egyptians accurately set the year as 365 days. This setting provides the basis for the modern Gregorian calendar. Their wisdom and observation not only revealed the mysteries of the seasons, but also provided valuable information for future generations to understand astronomy and time.