1. Measuring Earth Midterm Review Topics: Earth’s true shape & evidence Positions on Earth (Latitude, Longitude, Angle of Polaris) Time Zones

2. Earth’s true shape & evidence 1. Earth’s True Shape: Oblate Spheroid -bulging at Equator, flattened at poles -due to Earth’s rotation

3. 2.Evidence: a. Weight of an object is greater on the North Pole than the equator WHY?- Closer to Earth’s center on Poles so force of gravity is greater

4. 2.Evidence: b. Ships seem to sink below the horizon due to Earth’s curved surface (sphere)

5. 2.Evidence: c. Earth’s shadow during an eclipse is curved

6. 2.Evidence: d. Photographs from space

7. Remember: Equatorial Diameter= 12,756 km Polar Diameter= 12,715 km -Earth is almost perfectly round, so it appear to be a perfect sphere!

8. Positions on Earth (Latitude, Longitude, Angle of Polaris) 1. Latitude lines - run West to East around globe -Measure degrees north and south of Equator -LAT is fLAT Up to 90 o N Up to 90 o S

9. Angle of Polaris and Latitude ► Polaris can only be seen in Northern Hemisphere ► Angle of Polaris from horizon= Latitude

11. Polaris at center of Star Trails ► Polaris is stationary- does not move in sky

12. Star Trail Times ► Earth rotates once in 24 hrs ► To rotate, it must travel 360 o ► 360 o = 15 o /hour 24 hrs 24 hrs

13. Practice 1: During the time exposure of a photograph, the stars appear to have moved through an arc of 60° around Polaris. How many hours did this time exposure take? 4 hrs Practice 2: A time exposure photograph was taken for 8 hours. During that time, how many degrees of an arc did the stars appear to have moved? 120 o

14. 2. Longitude lines - run North to South around globe -Measure degrees West and East of Prime Meridian (Greenwhich, England) -Prime Meridian is 0 o -LONGitude- LONG lines 180 o W of Prime Meridian 180 o E of Prime Meridian

15. Degrees to Minutes to Seconds ► Minutes and Seconds are a break down of degree Latitude and Longitude ► Each degree is broken down into 60 minutes or 60 ' ► Each minute is broken down into 60 seconds or 60" ► (It's just like cm and mm on a ruler)

16. Time Zones ► We know from Star Trails that Earth rotates 15 o /hr ► We know that the sun rises in the East and sets in the West SO… ► West of the Prime Meridian is earlier ► East of the Prime Meridian is later

17. In the U.S.

18. Remember: The Earth is rotating The sun does not actually move around the Earth