how to describe why the length of day and night changes;
You will learn
to explain reasons why places where the Sun rises and sets change;
to indicate the height of the Sun at noon.
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Modern aircraft can travel with the same speed with which the Earth rotates around its own axis. As a result, you can fly for many hours and see the sunset the entire time!
You already know that the Earth’s rotation is the reason for the apparent movement of the Sun on the celestial sphere. In its apparent daytime journey, the sun first rises above the horizon, then rises higher on the celestial sphere, reaches its zenith, falls lower and finally sets.
The most commonly known consequence of the Earth’s rotation is the day and night cycle. Each time the Earth rotates around its own axis, a part of our planet’s surface faces the Sun – experiencing day, while at the same time another part of its surface faces away from the sun – experiencing night. The constant rotation of the Earth causes both zones (facing the sun and hidden in shadow) to move. At the same moment in time, it’s noon on one side of the Earth, while on the other side of the globe it’s midnight.
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Task 1
Explain why in all over Poland the Sun reaches its zenith at the same exact time. Justify your answer.
How does the Sun’s movement changes throughout the year?
The inclination of the Earth’s rotational axis in relation to its orbit is the reason why places where the Sun rises and sets change and why its height over the horizon at noon changes. As a result, the Sun rises exactly in the east and sets exactly in the west all over the world only twice a year (on equinox days). On the remaining days, sunrises and sunsets each day occur in different places.
Task 2
Before you watch the film titled “The Earth’s rotation”, write down a research question and a hypothesis. While watching the film, write down your observations and, at the end, your conclusions.
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Exercise 1
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Exercise 2
Summary
All periods of day and night occur at the exact same time in different places on Earth.
The inclination of the Earth’s axis and its rotation are reasons for change in observed places where the Sun rises and sets as well as its height above the horizon during its zenith.
Homework
Task 3.1
Use a compass to precisely designate east and west directions at the place where you live. Then observe where the Sun actually rises and sets.
Keywords
celestial sphere, Earth’s rotation
Glossary
polar day
polar day
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dzień polarny – zjawisko utrzymywania się Słońca przez przynajmniej całą dobę powyżej linii horyzontu
polar night
polar night
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noc polarna – zjawisko utrzymywania się Słońca przez przynajmniej całą dobę poniżej linii horyzontu