Build a Nile flood Sirius Calendar

Children learn how in ancient times observations of the sky helped people to measure the time of the year in which natural phenomena such as the Nile flood took place. These observations allowed them to prepare themselves for the harvest and the next flood. In this way, the children will realise that the calendar is based on long-term natural cycles.

After this activity, the children will be able to:

• describe that natural phenomena are often periodic.
• understand that the Nile flood happens every year around the same time.
• describe that the Nile flooding season was used to set up a calendar.
• describe that certain astronomical periods are aligned with seasons and help to determine their arrival.

In order to spark the conversation of periodic natural phenomena, the teacher can ask the children how they know that a year has passed. What are the changes around them that happen throughout a year? The children can also discuss the purpose of a calendar (e.g. agriculture). The teacher should also ask the children, why they think that for the ancient Egyptians it was so important to predict the season of the Nile flood. He/She should try to let the children discuss how a calendar would have helped to predict it. With the help of the Nile flooding calendar the children built, they will explain the importance of stars like Sirius becoming visible again.

• A set of Sirius-calendar consisting in two discs
• Scissors
• A round split pin

For more than 4000 years the lives of people in Egypt depended strongly on their crops. Predicting the flood of the Nile became very important because two month after the flood people could plant seeds in the fruitful soil. In that period Egyptian astronomers observed that each time the star Sirius appeared for the first time at the Eastern part of the sky just before sunrise, the Nile flood took place. This repeated again and again. For this reason the first appearance of Sirius at that position just before sunrise played such an important role.

Cut out the two discs and also the white window on disc 2.

On disc 1, write the names of the 12 months of the year in the corresponding empty spaces separated by the yellow lines, starting with August. For this, keep in mind that in August Sirius becomes visible at the East. Now make a small hole in the center of the two discs and fix them together with a split pin. You can now rotate disc 2 over disc 1 counterclockwise.
When looking at the Sirius-calendar, describe what happens with the Nile soil each four months. What happens when Sirius appears at the sky? What is the Egyptian farmer doing in each period? Observe the pictures and describe.

Fig. 8 The Sirius-Nile calendar (Credits: Scorza)

Fig. 9 Form to build the Sirius-Nile calendar (Credits: Scorza)

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