# Babylonian Astronomy

Astronomy in Babylon . The Babylonians studied the movements of the Sun and the Moon to perfect their calendar . They used to designate as the beginning of each month the day after the new moon, when the first lunar quarter appears. At the beginning this day is determined by observation, but later the Babylonians tried to calculate it in advance.

## Origin

The earliest known astronomical activities of the Babylonians date back to the 8th century BC. It is known that they accurately measured the month and the revolution of the planets .

The oldest observation of a solar eclipse also comes from the Babylonians and dates back to June 15, 763 BC. The Babylonians calculated the periodicity of eclipses , describing the Saros cycle , which is still used today. They built a lunar calendar and divided the day into 24 hours. Finally they bequeathed us many of the descriptions and names of the constellations .

## Discoveries

Around 400 BC they found that the apparent movements of the Sun and Moon from west to east around the zodiac do not have a constant speed . It seems that these bodies move with increasing speed during the first half of each revolution to an absolute maximum and then their speed decreases to the original minimum. The Babylonians tried to represent this cycle arithmetically by giving, for example, the Moon a fixed speed for its movement during half of its cycle and a different fixed speed for the other half.

They further refined the mathematical method by representing the speed of the Moon as a factor that increases linearly from minimum to maximum during half its revolution and then falls to minimum at the end of the cycle. With these calculations the Babylonian astronomers could predict the new moon and the day on which the new month would begin. As a consequence, they knew the positions of the Moon and the Sun every day of the month.

In a similar way they calculated planetary positions, both in their eastward movement and in their retrograde movement. Archaeologists have unearthed cuneiform tablets showing these calculations. Some of these tablets, which have their origin in the cities of Babylon and Uruk , on the banks of the Euphrates River , bear the name of Naburiannu (around 491 BC) or Kidinnu (around 379 BC), astrologers who must have been the inventors of the calculation systems

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