1. Investigation 2 Part 1
Sailing ships

2. Shape of earth
Okay, you all know that Earth is round – a sphere. But the more important question is, how do you know it is round?
Update Moon Log
Take a few moments to have a student update the class Moon Log, and remind students to keep up with their daily observations.
2. Discuss the shape of Earth
Students will know that our planet is round, or, more accurately, nearly spherical. Read slide.
Possible responses:
I just always knew Earth is round (story)
Globes representing Earth are round (model)
Pictures from space show Earth is round (since 1960s)
Christopher Columbus discovered it in 1492 (popular misconception)
Tell students that people didn’t always think Earth was round. They had to figure it out from evidence. Ask,
“How did people more than 2000 years ago (14 centuries before Columbus) figure out that Earth was round?”

3. Earth models Map Globe Features of both are drawn to the same scale
3. Introduce Earth models
Hold up the two models of Earth, the flat Earth (map) and the round Earth (globe). Point out that the features on the two models are drawn to the same scale; the continents and the ocean are the same size on both models. The polar areas appear larger on the flat Earth because the globe has to be stretched at the poles to fit on the rectangular map.
Each group (of four) will have a round Earth and a flat Earth to share. Caution students to handle the globes with care – no tossing them around in the air like balls.
4. Distribute Earth models
Have Getters get a map and a globe. Let groups look over the models and start thinking about ways to gather evidence to support a round or flat Earth.

4. Review latitude and longitude
Locate 0°, 0° (latitude and longitude) on the globe. What is there?
Find the site of Eratosthenes’s historical observation in Egypt, near where the Nile River crosses the tropic of Cancer. What is the latitude and longitude?
What is the global location of Reno, Nevada?
5. Review latitude and longitude
Establish some descriptive terminology to help students find their way around Earth. Ask students to focus their attention on the globe. Open the “Latitude and Longitude” multimedia, and have it ready to use as you guide the observations.
Read,
Find the lines that run around the globe. These are lines of latitude (like ladder rungs.) The longest line of latitude is the one that runs around the middle (the fattest part) of the planet, halfway between the North and South Poles. This is the equator.
All other lines of latitude are described in terms of their distances north or south of the equator. The unit of measure is the degree: the farther from the equator, the greater the number od degrees. It is 90° from the equator to either of the poles. The line of latitude circling the globe halfway up to the North Pole would, therefore, be 45° north. Halfway to the South Pole would be 45° south.
Find the lines that run from the North Pole to the South Pole (top to bottom) on the globe. These are lines of longitude.
Line of longitude extend from pole to pole. Each line is measured in degrees as well, with the starting line being the one that runs through an English town called Greenwich, the site of the Royal Observatory. That’s 0° longitude, and it is also known as the prime meridian. You can go east or west around the planet from there. If you land in New York, you are about 75° west (this is west of the prime meridian), and if you end up in Kobe, Japan, you are 135° east.
You could, of course, get to Kobe from the prime meridian by going far enough west. So you could think of Kobe as being 225° west, but the convention is that you count degrees only up to 180° (halfway around the world) east or west.
The line that is half a world away from Greenwich (which passes through the cluster of South Pacific islands called Fiji) is 180° longitude, frequently referred to as the 180th meridian, or the international date line.
Answers:
It is in the Atlantic Ocean, south of Ghana.
About 24° north latitude, 33° east longitude.
About 39.5° N, 119.8° W
Students should define longitude, latitude, and equator in their own words in their notebooks and add the words to their vocabulary indexes.

5. Focus question
How do observations of ships at sea provide evidence of Earth’s shape?
DO NOT answer at this time.
6. Focus question: How do observations of ships at sea provide evidence of Earth’s shape?
Pose the focus question, write or project it on the board, and have students write it in their notebooks.
- How do observations of ships at sea provide evidence of Earth’s shape?
Students do not need to answer the question at this time. They will return to the focus question later.

6. 7. Introduce models of sailing ships
After a few minutes, suggest making some model sailing ships and observing them sail on the two Earth models. Tell students,
“It is not possible to observe real ships sailing to and from port, so you might want to set up a simulation in which a tiny model ship sails across the flat and round Earth models.”
8. Demonstrate ship building
Project notebook sheet 5, Shape of Earth. Show students the sailing-ship model, and demonstrate the procedure for making the little silhouette boat on the end of a straw.
9. Distribute materials and make models.
Have Getters get a straw for each member of their group and two pairs of scissors for group members to share. Circulate among the groups; leave a strip of masking tape about 30 cm long at each table for students to share.

7. Sea voyages and observations
Get as close as possible to the starting point with your eyes.
Use notebook sheet 5 to record your observations.
10. Describe sea voyages
When students have completed their boats, call for attention. Show them how to select a starting port (e.g., Anchorage, AK) and a destination port (perhaps Auckland, New Zealand), and sail their boat from one port to the other.
Show them how to get their eyes down as close as possible to the starting point. They want to have the view as though they are on the ground at that position on Earth, not viewing Earth from space. It is easier if a partner holds the map or globe for the observer, then trade, so everyone observes their sailing ships on the flat maps and globes.
11. Record observations.
Distribute a cope of notebook sheet 5, Shape of Earth, to each students and have them review the sheets. Use the projected image of this sheet to point out the places for three sequential drawings of the ship sailing on the flat Earth and three drawings on the round Earth. The first drawing in each sequence should show what the boat looks like ready to sail, the second should show what it looks like some distance from port, and the thir should show what it looks like far from port.

8. confirmation
wdf-ucm- webContent/Contribution%20Folders/FOS S/multimedia/middle_school_html5_asset s/Tutorials/earth_models/index.html
12. Observe students with the models
Circulate among students as they work, reminding them to get their eyes right down at globe or map level (on the beach) in order to make their observations. As you visit each group, ask them to explain why their ship looks as though it sinks as it sails over the horizon, and check their progress on their notebook sheets as they draw images to represent what they are observing.
13. Confirm “sinking” appearance of ship
Some students will have a hard time shifting their perspectives and realizing that the ship looks different in each model, “sinking” with the round Earth model and “shrinking” with the flat Earth model.
Show students the “Earth Models” video from FOSSweb, and have volunteers point out the differences in the ship’s appearance as it sails away, comparing the Flat Earth Views and the Round Earth Views. Make sure all students have observed the phenomenon of the “sinking” ship.

9. Historical information
Observers from land saw a ship sink below the surface.
Sailors in the crow’s nest would see land minutes before the crew on deck would.
14. Present historical information
Tell students,
“For centuries, shops sailed the open seas, carrying materials and goods, such as metals, food, and household products, from port to port. Merchants on shore waiting for the next delivery from sea would often observe the arriving ship rise out of the sea, first the topsail, then the mainsail, and finally the deck and hull. The same observers would report that the ship sailing from port seemed to sink into the sea, disappearing below the surface until just the topsail was visible. They might well have wondered why this happened.
The sailors on board the ship also logged interesting reports. Sailors always kept constant lookout in all directions and from all locations on a ship at sea, watching for dangers and for land. Interestingly enough, it was always the sailor in the crow's nest near the top of the mast who first sighted land. Sailors on deck would stare in vain for their first glimpse of land. It would be several minutes before land would come into view for the crew on deck. Why did the lookout in the crow’s nest always see land first?”

10. Answer the focus question
Which theory of the shape of Earth is best confirmed by the observations of the two models of Earth?
Answer the focus question with that in mind.
15. Answer the focus question
Ask students to talk in their groups to decide which theory of the shape of Earth is best confirmed by the observations of the two models of Earth. This is a good time for students to answer the focus question in their science notebooks.
How do observations of ships at sea provide evidence of Earth’s shape?
16. Clean up
Have students return the globes to the bags. Have Getters return the globes and maps to the materials station.
---POSSIBLE BREAKPOINT---

11. simulations
Is it possible to conduct every experiment or make every observation? Why or why not?
17. Introduce the simulation
Tell students that it is not always possible for people to conduct every experiment or make every observation that will help them understand a new concept. However, modern multimedia technologies can provide a simulated (representative or model) experience that permits the multimedia user to observe and interact in ways that are similar to reality.
Reorganize the class for multimedia viewing.
18. Describe the “Round Earth/Flat Earth” simulation
Tell students that the “Round Earth/Flat Earth” simulation will allow them to sail a ship across the seas and observe a lighthouse as they sail away from or toward land. Or they can observe the ship sailing to or from land from the point of view of someone on land.
TEACHING NOTE: There are many variables that can be controlled as the ship sails, allowing students to make more kinds of observations than anyone could in the real world.

12. Simulation Round Earth Sailing from the dock
View from land at sea level
19. Demonstrate simulation
Go to “Round Earth/Flat Earth” on FOSSweb. Select a set of sailing parameters, describe each setting as you select it, and then run the simulation as a demonstration. To start, use these settings:
Round Earth
Sailing from the dock
View from land at sea level
Ask students what they noticed as the ship sailed away. Repeat the process, but this time view the ship through the telescope, and ask students if they noted anything else. (They can see the tip of the mast as it disappears over the horizon.)

13. Review What happens when you change your point of view?
20. Review point of view
Tell students,
“Each time the ship sails away or returns to the port, you are in a position to make observations, either on the ship, on the land, or out in space looking at the whole scene. Your position of observation is your point of view.”
Answer: You see different things, you get different information, you get more data about the same event.

14. Horizon and line of sight
What is the horizon?
21. Discuss horizon and line of sight
Ask question on board. (The imaginary line where the sky meets Earth or the ocean.)
The multimedia user can change the point of view to be an observer in the action or an external observer not involved in the action. Lines superimposed on the external-viewer scene represent the line of sight afforded by the various points of view. Point these out – they may help students understand how a ship can appear to sink below a curved surface. The place where the line of sight meets the water is the horizon. We can see only down to the horizon, no lower. We can’t see over the horizon.
Students should define line of sight and horizon in their own words in their notebooks and add the words to their vocabulary indexes.

15. Compare horizon
How is the horizon different for the flat Earth and the round Earth?
22. Compare horizon
Ask question on board. (With the flat Earth, the horizon is far away, at infinity. Things moving away get smaller and smaller but never seem to reach the horizon. With the round Earth, the horizon is much closer. Ships going beyond the horizon appear to sink into the ocean.
23. Continue exploration
To understand the thinking that led ancient mariners to conclude that Earth was round, students should have as much opportunity to work with the simulation as possible. Students can access the multimedia at home on FOSSweb, using the class login that you have set up.
TEACHING NOTE: In Extending the Investigaiton, an activity uses additional data to confirm that Earth is round. It is a wonderful opportunity to delve deeper into the historical development of scientific understanding.
24. Extend the investigation with homework
“The First Voyage of Columbus” is an optional reading that can be assigned as homework. Have students respond to the questions at the end of the article on a separate sheet of paper, collect the papers, and grade and return them to students so students can affiz them into their science notebooks.

16. Response sheet Remember our simulations of Round Earth and Flat Earth.
25. Review vocabulary
26. Assess progress: response sheet
Distribute a copy of notebook sheet 6, Response sheet – Investigation 2, to each student. Have students rea the text and work independently to respond to the ideas presented.
WHAT TO LOOK FOR:
Students recognize that the horizon formed by the sea establishes a visual barrier where it meets the sky.
Students indicate that ships sailing beyond the horizon sail down the curvature of Earth, resulting in the illusion of ships sinking.
Students indicate that ships on a flat Earth diminish in size, but do not appear to sink into the ocean.