Shape of the Earth
Understanding the Shape of Earth
- The Earth is not a perfect sphere but an oblate spheroid, meaning it is slightly flattened at the poles and slightly wider at the equator.
- This flattening is due to Earth's rotation. The centrifugal force at the equator is greater than at the poles which causes the equatorial bulge.
- The Earth's equatorial diameter is about 12,756 km and the polar diameter is about 12,714 km. This difference is negligible considering the overall size of Earth, which is why we often refer to Earth as a sphere for simplicity.
- Despite the slight variation from a perfect sphere, the Earth's shape is very close to spherical. Any variations in topography (mountains, valleys, etc.) are relatively minuscule.
Earth's Surface
- The surface of Earth is divided into two main types: land and water. While water covers about 70% of Earth's surface, land makes up the remaining 30%.
- The largest bodies of water are the oceans, and the largest land masses are the continents.
- The Earth's surface is constantly changing due to processes such as erosion, weathering, tectonics, and volcanic activity. These processes contribute to the geographical features we see.
The Geoid
- A more precise definition of Earth's shape is the geoid.
- The geoid represents the shape that the ocean surface would take under the influence of Earth's gravity and rotation alone, in the absence of tides and currents.
- The geoid is used as a reference surface from which topographic heights and ocean depths are measured.
Determining Earth's Shape
- Over time, various strategies have been used to determine Earth's shape, including viewing lunar eclipses, measuring shadows in different locations, and the use of modern technology such as satellite data.
- Measurements from the technology like GPS, ultra-precise leveling and satellite laser ranging have confirmed Earth's oblate spheroidal shape.