1. 1-1 The Shape of the Earth Unit 1: Planet Earth September 24, 2011
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2. Shape of the Earth Earth is nearly a perfect sphere.
Earth is an oblate spheroid, slightly flattened at the poles and bulging a little at the equator.
May 24, 2019
1-1 Shape of the Earth

3. Not a Perfect Sphere? Earth looks flat on its surface.
Due to its daily rotation, Earth bulges about 40 kilometers at the equator.
Earth looks flat on its surface, the Earth is nearly 13,000 kilometers (8000 miles) in diameter. Due to its daily rotation (spin), Earth bulges about 40 kilometers at the equator. Still, Earth is so close to the shape of a sphere that from any point in space it looks like a perfect sphere. Even the tallest mountains are insignificant when we compare them with the size of our planet. From outer space Earth looks perfectly round and smooth.
South Dakota
May 24, 2019
1-1 Shape of the Earth

4. Oblate Spheroid
Still, Earth is so close to the shape of a sphere that from any point in space it looks like a perfect sphere.
An Oblate Spheroid is a nearly perfect sphere.
May 24, 2019
1-1 Shape of the Earth

5. How do we know that we live on a gigantic sphere?
We have photographs of Earth taken from space.
There other pieces of evidence of the shape of the earth.
All of them show Earth’s round shape. In addition, we notice the changing positions of the sun and stars, especially Polaris, as we move over great distances on Earth. These changes are consistent with the expected changes as we move over a round planet.
May 24, 2019
1-1 Shape of the Earth

6. Earth’s Shape
At right are sailboats. As they move toward the round horizon, they appear to sink.
At right is a picture of a lunar eclipse. The shadow is cast by the round earth on the moon.
How do we know that we live on a gigantic sphere? We have photographs of Earth taken from outer space. These changes are consistent with the expected changes as we move over a round planet.
May 24, 2019
1-1 Shape of the Earth

7. The North Star May 24, 2019 1-1 Shape of the Earth
All of them show Earth’s round shape. In addition, we notice the changing positions of the sun and stars, especially Polaris, as we move over great distances on Earth.
May 24, 2019
1-1 Shape of the Earth

8. The North Star
We notice the changing positions of the sun and stars, especially Polaris, as we move over great distances on Earth.
All of them show Earth’s round shape. In addition, we notice the changing positions of the sun and stars, especially Polaris, as we move over great distances on Earth.
May 24, 2019
1-1 Shape of the Earth

9. May 24, 2019
1-1 Shape of the Earth