1. Earth/sun relationship
Investigation 2 part 2
Earth/sun relationship

2. Hello darkness, my old friend
Have you ever thought, “What is night?”
Write at least 2 sentences answering:
What causes night?
Update Moon Log
Take a few moments to have a student update the class Moon Log, and remind students to continue their daily observations.
2. Assess prior knowledge: quick write
Most students have ideas about how day and night occur. Find out what those ideas sure, using a quick write. Distribute a quarter sheet of paper or an index card to each student.
WHAT TO LOOK FOR:
Students write that the side of Earth facing the Sun is always illuminated, and the side facing away from the Sun is always dark (in shadow).
Students write that the side of Earth facing the Sun is always changing because Earth spins on its axis.
Students write that Earth rotates counterclockwise (looking down from above the North Pole), and it takes 24 hours to make one complete rotation.

3. What is night, and what causes it?
What are some ideas?
3. Discuss night
Call on a few students to share their ideas about night.
Possible explanations:
When it’s dark.
When the Sun goes down
When the Sun is on the other side of Earth.
When the Sun goes behind clouds.
When the Sun is behind the Moon.
When Earth spins so we can’t see the Sun.
When we are in the shadow of our own planet. (A rare response).

4. What is day, and what causes it?
What are some ideas?
4. Discuss day
The list will probably read like a reciprocal of the first list.

5. Focus question What causes day and night? DO NOT answer at this time.

6. Lamp as a model
Is there any way we could use this lamp to test some of your ideas about day and night?
6. Introduce a lamp as the model Sun
Bring out the lamp, and propose using it as a model Sun.
Ask question on board.
Say, “I’m going to put it here in the middle of the room, and you can move around and try some things to demonstrate how day and night work.”
Let students work out ways to tackle this challenge.

7. 7. Review and refine the simulation
After a few minutes, interrupt the action, and help students understand how to establish a working model of Earth and the Sun.
The lamp in the center of the room is the Sun.
Your head is Earth.
One of your eyes is an observer on Earth.
Move yourself to demonstrate how your observer (eye) can experience day and night on your Earth (head).
So that everyone has enough room, stay about 3 m from the Sun and out of one another’s shadows.

8. Day/night movements
Which statements explain day and night most effectively? Can we add or refine?
8. Introduce an additional challenge
Once students can model day and night, challenge them to position themselves so that their “observer” is seeing noon and then midnight.
9. Discuss day/night movements
Refer to the lists of day and night definitions. Ask the class which of the statements seems to explain day and night most effectively. Students may have some new ideas to add to the original list. Let one or two students demonstrate how Earth’s motion can produce day and night.

9. Challenges
Rotate so that your observer is experiencing day, then night.
Rotate so that your observer is experiencing noon.
Rotate so that your observer is experiencing midnight.
Rotate so that your observer is experiencing sunrise.
Rotate so that your observer is experiencing sunset.
10. Introduce rotation and axis
Tell students,
“When an object turns in a circle or spins like a top, we refer to that motion as rotation. The imaginary shaft on which the object turns is called an axis. Earth rotates on an axis that runs through its center from the North Pole to the South Pole.
11. Consider the orientation of Earth to Sun
Give students the challenges on slide.
TEACHING NOTE:
These last two challenges will cause the most problems for students. There may be some finger-pointing and questioning of students facing different directions. Give them time to decide which way they should be facing.

10. Earth’s rotation Which way does Earth rotate?
Clockwise or counterclockwise?
12. Figure out Earth rotation
After students have struggled with sunrise and sunset for a few minutes, call for attention. Tell students,
“I noticed some of you were facing left to demonstrate sunrise, and some of you were facing right. Both can’t be accurate. Let’s see if we can figure out which way Earth rotates so we can demonstrate sunrise accurately. Let’s operate on one agreed assumption. The top of your head is your Earth’s North Pole.”
13. Discuss rotation
Ask students to report the direction of Earth’s rotation in terms of clockwise or counterclockwise as viewed down on Earth from above the North Pole. Have one student demonstrate and explain his or her conclusion. Ask other students if they concur. There may or may not be agreement that Earth rotates COUNTERCLOCKWISE.
If students are still struggling with direction, offer a series of hints and questions to guide their thinking. Tell them to go back to the visualization of a map of the US on their faces. Ask,
-”Stand so it is just sunrise in New York. When it is sunrise in New York, is it day or night in California? (Night)
“Turn so it is just sunrise in California. When it is sunrise in California, is it day or night in New York? (Day)
Keep turning so that it is day in both places. What direction did you turn to do that? (To the left, or counterclockwise.)

11. modeling Daytime Midnight Nighttime Sunrise Noon Sunset
14. Reinforce day and night with globes
Ask students to form collaborative groups. Let a Getter from each group get a globe. Position the lightbulb “Sun” in the center of the room, and turn out the lights.
Start the action by having students verify the direction of Earth’s rotation. Ask them to imagine that there is an observer on the globe in the location of your school. Challenge students to orient their globes so the observer is experiencing the situations on the slide.
Ask students to pay attention to where the Sun is with respect to the observer in each case above. If students are struggling, ask them to think about their dual points of view. They have to change their frames of reference from on Earth, looking “up” to above Earth, looking down.
15. Record vocabulary.
16. Extend the investigation with homework
Students will be working with notebook sheet 7, Day/Night Think Questions, later in the investigation, and might benefit from thinking about the questions at home first. Students can write answers on separate sheets to be collected or on a facing page in their notebooks.
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12. Notebook entry Make a diagram showing Earth’s rotation.
Label the rotation and axis and a short explanation.
17. Confirm Earth’s rotation
Confirm with students that Earth appears to rotate counterclockwise if seen from above and that in their model, they were turning to the left to represent this. Ask students to make a notebook entry with a diagram showing Earth’s rotation, labeling the rotation and axis, and to write a short explanation.

13. Demonstration with globe
How should I set up the model? Where should the Sun be, and where should Earth be?
18. Demonstrate day and night with a large globe
Show students a large globe and the light source. Ask question on slide.
Use guidance from students to set up the model with the Sun in the center of the room and Earth positioned some distance form the Sun. Ask a student to rotate the globe to demonstrate a day/night cycle: midnight, sunrise, noon, sunset. You might want to let students move around the system to observe it from different angles.

14. What makes the Sun “come up” and “go down”?
Why is it dark at night?
At any given time, how much of Earth is in daylight and how much is in darkness?
What makes the Sun “come up” and “go down”?
Does the Sun come up in the morning all over the world? Explain.
19. Discuss day and night
Use notebook sheet 7, Day/Night Think Questions, to help students clarify their thinking about day and night. Project the sheet to model thinking about the first four questions.
TEACHING NOTE:
If you gave the notebook sheet as a homework assignment, students should use this time to revise their responses. They should use colored pencils or a line of learning to indicate new thinking, instead of erasing their original ideas.
Focus on the first question: Why is it dark at night?
Let students discuss the question in their groups for 1 minute.
Give students 1 minute to write or revise their answers in their notebooks.
Continue with questions 2-4.
At any given time, how much of Earth is in daylight and how much is in darkness?
What makes the sun “come up” and “go down”?
Does the Sun come up in the morning all over the world? Explain.
Give students minutes to complete or revfise answers to the rest of the questions.

15. Key points
The Sun is aluminous object that gives off light. The Sun is a source of light that illuminates Earth during the day.
When light falls on an object, the portion in the path of the light is illuminated. The area behind the object is in the shadow, in the dark.
When light falls on a spherical object, like a planet, exactly half is in the light and half is in the dark.
20. Summarize day and night
When students have answered all the questions, summarize day and night with a few comments, including these key points (on slides).

16. Key points continued
The dark side of the sphere is in its own shadow, not the shadow of another object.
Day and night are the names given to the light and dark halves of a planet.
The Sun is stationary (essentially) and Earth rotates on its axis once every day, giving the illusion of a Sun that rises and sets.

17. Key points continued
If a planet didn’t rotate, it would have a day side and a night side just the same as a planet that does rotate. The difference is that, when a planet rotates, the part of the planet experiencing day and the part experiencing night changes continually; if a planet didn’t rotate, one half would experience day all the time, and one half would experience night all the time.
One complete rotation of our planet accounts for one complete day. For Earth, one rotation requires 24 hours (1 day).

18. question How does Earth move relative to the Sun?
21. Introduce revolution
Ask question on slide.
Answer: Earth revolves (travels around) around the Sun.
Demonstrate how Earth revolves around the Sun by carrying the globe in a counterclockwise circle around the lamp. Point out to students that the revolution is counterclockwise, just like the rotation.

19. Next question
How long does it take Earth to make one revolution around the Sun?
21. Continued
TEACHING NOTE:
If students ask about leap years, you can point out tat the revolution is actually days, which is why every 4 years we add 1 day to the calendar.
Ask on slide.
Answer: 1 year or days
Tell students,
“People often think that Earth moves in an oval, or elliptical, shape as it orbits. In face, the orbit of Earth is nearly circular.
Earth’s orbit is slightly elliptical. We introduce it here as “nearly circular” to address the misconception that many students have that the orbit is more like an oval than a circle. This misconception will be addressed further in Investigation 3.

20. Earth’s axis
How long does it take for Earth to rotate (turn around once) on its axis?
22. Discuss Earth’s axis
Ask students to explain how the revolution of Earth is different from the rotation of Earth, which they learned about earlier in this part. (Revolution is the orbit of Earth around the Sun ; rotation is Earth’s spinning on its axis.)
Tell students,
“Earth has a North Pole and a South Pole. These are the north and south ends of an imaginary axle, called an axis, on which Earth rotates.”
Use your globe to demonstrate how Earth turns around like a top. Identify this kind of motion as rotation. Ask question on slide. Answer (1 day or 24 hours.)
Point out that Earth does not spin straight up and down on its axis, but is tipped over at a significant angle of 23.5° relative to the plane of its orbit.

21. North star Named Polaris
North Pole points toward Polaris due to the 23.5° tilt of Earth.
23. Introduce North Star
Tell students,
“There is a star in the night sky called Polaris, or the North Star. It is positioned almost directly over Earth’s North Pole. Earth’s North Pole points toward the North Star – summer, fall, winter, spring, day, and night. That’s why the North Star has been a navigation aid to seafarers and explorers in the Northern Hemisphere for centuries. In our Earth/Sun system, we need a North Star. You will have to visualize the North Star through this wall and way, way off in the distance. The North Pole of our model Earth will always point its axis at the North Star as it revolved around our model Sun.”
Point out the North Star you have placed on the wall.
“We can use this star to remind us of approximately where the North Star is in the sky.”
TEACHING NOTE:
Make sure students understand that the North Pole is tilted 23.5° relative to its orbital plane, pointed in the same direction – aimed toward the North Pole.
Demonstrate Earth’s orbit by carrying your globe in a counterclockwise circle around your Sun, making sure to honor the 23.5° tilt of the axis and ensuring that the North Pole tilts toward the North Star at all times.

22. 24. Record vocabulary
25. Assess progress: self-assessment
Return quick writes from step 2. Have students revise answers.
WHAT TO LOOK FOR:
Students write that the side of Earth facing the Sun is always illuminated, and the side facing away from the Sun is always dark (in shadow).
Students write that the side of Earth facing the Sun is always changing because Earth spins on its axis.
Students write that Earth rotates counterclockwise (looking down from above the North Pole), and it takes 24 hours to make one complete rotation
26. Extend the investigation with homework
Students can use the “Day/Night” simulation to explore the relationship between the Sun and Earth. Suggest that students first observe “Earth/Moon/Sun” at 90° and the Daily setting. Then they can switch to “Earth/Moon” at the Hourly setting, also at 90°.

23. Key points
Earth is tilted 23.5° on its axis, and the axis always points in the same direction, toward the North Star.
One rotation of Earth takes 24 hours, producing the day/night cycle on Earth.
Earth revolves around the Sun in a circular orbit once every days.
Wrap-up
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I-Check 1-2