Patterns

In this lesson, students apply their knowledge of matter to figure out phenomena in the solar system evaluating how patterns result from the specific movements and positions of the Sun, Moon, and Earth. They discuss how Earth’s rotation on its axis causes day and night and Earth’s orbit causes seasons. They then analyze how the position of the sun in the sky affects the length of shadows and the length of daylight hours in the winter and summer seasons.

• The movement of objects in the solar system create patterns that people can use to mark the passage of time. 
• Movement in the solar system is predictable, and results in patterns that we see here on Earth. 
• As Earth rotates on its axis, part of Earth faces the sun and part of Earth faces away from the sun. The sun appears to move across the sky throughout a day, and then appears to disappear at night. 
• Shadows are dark shapes created when an object blocks light. Shadows change throughout the year because of the position in the sky depending on the season. The height of the sun in the sky is related to the length and direction of shadows cast by different objects. The sun rises in the east and sets in the west.
  
  

• Why does the sun appear to travel across the sky throughout one day?
• How does Earth’s movement cause day and night?
• How does Earth’s movement help people measure time?
• What happens to the Sun when it is night?
• How are shadows formed?
• Why is your shadow longest when the sun is lowest in the sky, near the horizon in the early morning and evening?
• Why are shadows longer in the winter than they are in the summer?
• How does Earth’s tilt on its axis cause winter in the northern hemisphere?
• Why is it always summer in the southern hemisphere at the same time as it is winter in the northern hemisphere?
  
  

Misconception: Earth does not move.

Fact: Earth is in constant motion. It is continually orbiting the Sun, making one complete orbit around the Sun in one Earth year. At the same time, Earth rotates around its axis, causing day and night.

Misconception: he moon changes its size throughout the month.

Fact: The moon stays the same size. What changes is how much of the moon we can see from Earth because of the moon’s position relative to the Sun as the moon orbits Earth.

Gravity : a force of attraction between all matter

Pattern : something that happens in a regular and repeated way

Season : a period of time characterized by specific weather patterns and by the length of day and night

Shadows :  dark shapes created when an object blocks light

Solar System :  a collection of planets and other objects that orbit a star

Weight :  the gravitational force exerted on an object by a planet or moon; measured in newtons (N)

Day and Night

Earth rotates on an imaginary line that goes through Earth from the North Pole to the South Pole. This imaginary line is called an axis. Earth rotates very quickly. Earth completely rotates around its axis about once every 23 hours and 56 minutes (one Earth day).

The reason we don’t feel like we’re speeding through air is similar to how it can feel in an airplane like the plane isn’t moving. Gravity holds us all onto the planet, and so we rotate with it.

As Earth rotates, part of the planet gets light, and then dark. The sun always shines, but its light only hits one half of Earth at a time. This is why we have day and night.

The patterns in how the sun, stars, planets and moon move across the sky are caused by Earth’s movement. All of these objects appear to rise in the east and set in the west over one day because of Earth’s rotation.

Telling Time with Shadows

During the day, the sun appears to move across the sky. At dawn, the sun appears close to the ground in the east. As hours pass, it moves upward. By noon, the sun appears directly overhead. In the evening, the sun appears close to the ground again, this time in the west. At night, the sun appears to disappear.

Long ago, people noticed that as the sun rises in the east, it casts shadows that change throughout a day. Shadows are dark shapes created when an object blocks light.

The length and direction of the shadow depend on how low or high the sun is in the sky. When the sun shines down from directly above you, your head is the only part of your body blocking the sunlight. As a result, there is very little shadow. In the middle of the day, around lunchtime, your shadow will become very small. It might even disappear. In contrast, your shadow will be the largest when the sun is near the horizon. This is because your body blocks more light.

Changing Seasons

Shadows also change throughout the year. Shadows are much longer during the winter months than during the summer months.

Shadows change throughout the year because the sun appears in the sky at different heights depending on the season. A season is a period of time characterized by specific weather patterns and by the length of day and night. In the summer, the sun appears high in the sky. In the winter, the sun appears much lower in the sky.

We now know that the sun appears to be in different locations throughout the year because of Earth’s position in the solar system relative to the sun. As Earth moves around the sun, it is tilted 23.5 degrees on its axis.

Because of Earth’s tilt, the northern and southern hemispheres each receive different amounts of sunlight throughout the year. For half of the year, the northern hemisphere is tilted toward the sun. The sun appears to be high in the sky, so the sun’s rays shine more directly onto Earth, at a higher angle. When this happens, shadows are smaller and temperatures are warmer.

At the same time that it is summer in the northern hemisphere, it is winter in the southern hemisphere. This is because the southern hemisphere is tilted away from the sun. The sun is lower in the sky, causing the sun’s rays to hit Earth at a lower angle. This causes the sun’s rays to spread out over more space, causing longer shadows. It also makes temperatures cooler. For the other half of the year, the northern hemisphere is tilted away from the sun and the southern hemisphere is tilted toward the sun. Now it is winter in the north and summer in the south.

For the hands-on activity of this lesson, students investigate the phenomena of patterns in the sky and figure out how the position of the sun in the sky affects the length of shadows and the length of daylight hours in the winter and summer seasons. Students collect and analyze data on how the movement of the sun across the sky causes the length and direction of shadows to change over the course of a day. They also analyze sunrise and sunset times to determine the length of daylight hours in the summer and winter seasons. Students use their investigative data, along with their knowledge of atoms, properties, and positions/movement in the solar system, to determine how the movements of Earth, the Moon, and the Sun cause patterns of movement.