1. Earth’s Dimensions
Its true size and shape

2. What is the true shape of Earth?
It’s an OBLATE SPHEROID
Flat at the poles
Bulged at the equator
But it’s still pretty round!
Shaped a lot like a basketball!

3. Causes of Earth’s True Shape
Earth SPINS…
Faster at the EQUATOR and slower at the POLES
CENTRIFUGAL FORCE is what causes Earth to bulge at the EQUATOR! 2.
a. Faster rotation means GREATER C.F.

4. Evidence of Earth’s Shape
Space photos show Earth is pretty darn ROUND
Ships seem to disappear…Shows Earth is ROUND!
Eclipse of the moon…
Earth’s ROUND shadow is cast on the moon…

11. Still Daylight in the West!
AMERICAN CITIES at night
Curved Terminator Shows Earth is Round

12. It’s still daylight in California
Those light are Boston, New York, Philadelphia and Washington.
Dallas
Mexico City

13. Iceland
England
Atlantic
Ocean
France
Spain
Italy
AFRICA

14. Evidence of Earth’s Shape
You weigh MORE at the north and south POLES
You are closer to the
center of Earth at the poles
So there is more gravity!!
You are farther away at
the Equator… and weigh
LESS!

15. Evidence of Earth’s Shape
660
900
230 00
Polaris (the North Star) changes altitude because Earth is ROUND and the surface is CURVED

16. Latitude and Altitude of Polaris
If your latitude = 900N,
Polaris is ____above the
horizon
660
900
230
If your latitude = 00N,
Polaris is ____above the
horizon 00
The altitude of Polaris (the North Star) above the horizon= the latitude of the observer (you)

17. Latitude and Altitude of Polaris
Altitude of Polaris is about 410 above the horizon

18. Where’s Polaris?
Draw the 7 stars of the BIG DIPPER…
Sketch an arrow through the end of the cup to the BRIGHT STAR
The little dipper!
What’s this constellation?
That BRIGHT STAR is POLARIS!
It points NORTH!
Its altitude is your LATITUDE!
Get out there tonight and find it!