The correct answer to this open question is the following.
The appearance of Sirius in the east after a long absence told the ancient Egyptians that the Nile River would soon rise.
Ancient Egyptians were religious people that considered that its ancestors came from the starts and they like to observe the sky to try to interpret some events, That was the case of the star Sirius that when it appeared in the east after a long absence told the ancient Egyptians that the Nile River would soon rise. This prepared farmers to be ready because, after the flooding of the Nile, the banks had fertile soil to grow crops.
