Lesson 3: Earth's Shape

Lesson 3: Earth's Shape

1. Oblate Spheroid

   • oblate spheroid - a sphere that is slightly flattened
   • Earth is slightly flattened at the poles
   • Earth bulges as bit at the equator
   • Because of Earth's rotation, Earth is an oblate spheroid

2. Looks Flat

   • Because it is very large

3. Round

   • Photographs of Earth all show Earth's spherical shape
   • We notice the changing position of the sun and stars as we move great distances over Earth
   • An object's weight depends on distance to Earth's core, since weight doesn't change in different places, each point on earth is equidistant to to core

4. Diameter and Circumference

   • Circumference - the distance around a circle
     • Equatorial Circumference of Earth = 40,076 kilometers
     • Polar Circumference of Earth = 40,008 kilometers
   • Diameter - the distance through the center of an object
     • Polar Diameter of Earth = 12,714 kilometers
     • Equatorial Diameter of Earth = 12,756 kilometers
   • If Earth were a perfect sphere the Equatorial and Polar values would be equal