What is the size and the shape of the world?

Answer 1

The size is 12,713.54 km (poles) while the other side is 12,756.32.

If this was a circle, this had no "back"!!! Circles have no back.

If this was a sphere, this have back. BUT the size will change.

Example

The diameter of the both poles was 56 miles (for example) and the other side was 56 miles. (for example).

The world is slightly sphere. But this has flatness on both poles. You can compare it into an orange. Because of the mountains, hills and more, the world is like a zig- zag-forming-a-oblate-spheroid, curvy-line-forming-a-oblate-spheroid.

The world is a geoid (meaning earth-shaped) in shape - it is roughly a squashed sphere, an oblate spheroid; this is due to the rotation of the earth causing it to bulge around the equator.

How do you define size? The [average] radius, the surface area, the volume or the mass of the earth?

Radius ≈ 6,371 km ≈ 3,957 miles

Surface area ≈ 5.1 x 1010 hectares ≈ 1.97 x 108 square miles

Volume ≈ 1.08 x 1021 m3 ≈ 2.6 x 1011 cubic miles

Mass ≈ 5.98×1024 kg ≈ 5.89 x 1021 tons ≈ 6.59 x 1021 short tons