1. Aim: How can we use models to show Earth’s shape? (Topic III Notes #1)

2. What are some examples of models?
What are models?
What are some examples of models?
A model is anything that represents the “properties” of an object or a system.
Can be a miniaturized copy
May show things that cannot be seen
There are Five types of models

3. 1) Physical and Mechanical Models
Provide us with visual information.
Rely on our sense of sight.

4. 2. Mental Models
Models that exist in our mind
Usually cannot be made into a physical model
3. Mathematical Models
Show relationships that are expressed using mathematical symbols that express the properties of an object or a system.
Examples: D = m / v V = l x w x h

5. 4. Graphic Models
· Models that use graphs to show the nature of a relationship between one factor to another

6. 5. Computer Models:

7. Earth's Shape

8. Is the Earth flat?

9. Square?

11. A-Is the Earth a perfect sphere?
The Earth’s true shape is an oblate spheroid
It is slightly flattened at the poles and slightly bulging at the equator.

12. However, if drawn to scale, it looks like a perfect sphere!

13. Oblate Spheroid

14. There is only a 42 km difference between the polar diameter and equatorial diameter !

15. Which diagram represents the best shape of the Earth to scale?

16. B.
Evidence of
Earth's Shape

17. 1) a. As ships sail away from an observer, they drop below line of sight b. The rising and setting of the sun The sun can still be seen on tall objects after it sinks below the horizon.

20. 2. The shape of Earth’s shadow during an eclipse

23. 3. Photographs of Earth taken from Space

25. 4. Polaris (North Star)
The North Star is located directly above Earth’s axis

26. Therefore, the altitude of Polaris = the latitude of the observer!
This method of navigation can only be used in the Northern Hemisphere.

28. Astrolabe

31. Star Trails around Polaris