1. What evidence told scientists earth has a curved surface?

2. EVIDENCE Ships appearing and disappearing on the horizon
During an eclipse they saw the shadow of the earth and saw it was curved

3. Polaris
Polaris North Star
This is the star that lies in space practically over the geographic North Pole of the earth.
Position of Polaris
rotation of the dippers
If you stood at the North Pole,
Polaris would be Directly overhead
In the zenith position (90° angle)

4. Polaris and Latitude
As you go from the equator to the north pole Polaris gets higher and higher in the sky
As latitude increases so does the altitude of Polaris

5. Day and Night
Earths shape and rotation are responsible for the change of day to night.
If the Earth were flat the whole Earth would experience daylight at the same time.

6. Climate change with latitude
Each latitude is receiving different angles of sunlight.
The varying angles are responsible for our different climate zones.
If the earth were flat the whole earth would receive the same angle of sunlight and would experience the same climate.

7. What is the True shape of the Earth?
Oblate Sphere – slightly flattened sphere
Earth is bulging at the equator b/c of Centrifugal force
The polar diameter is shorter than the equatorial diameter.
Centrifugal force is the outward force on a rotating body.

8. How does measurements of gravity and weight prove the earth is an oblate sphere
Gravity is greater at the poles than it is at the equator
So the poles must be closer to the core than the equator.
The

9. You would weigh
slightly more at the poles
than at the equator b/c the pull
of gravity is stronger there

10. OBLATE SPHEROID The true shape of the earth is an oblate spheroid-
The next question is , what does an oblate spheroid, the true shape of earth look like?
Wow – good question- AND it will be answered in your next lab

11. Earth looks like a perfect sphere
(round and smooth)
Earth appears perfect to the naked eye, because the difference btn the polar and equatorial diameter is soooooo slight it’s insignificant