WHAT IS THE SHAPE OF THE EARTH? - SCIENCE - 2025

Generally speaking, the Earth is shaped like a sphere. That said, the actual shape of the Earth can be described much more specifically.

Mainly the Earth is a sphere; it is the simplest way to explain the geometric shape of our planet. Its approximate radius is 6371 km, usually it varies between 6353 and 6384 km depending on where it is measured from.

Now its specific real shape can be thought of as a rotational ellipsoid or an oblate ellipsoid. This would be the best definition to describe its correct shape if you wanted to be more precise.

This is because due to the constant rotation on its own axis, our planet is flattened at the two poles and is prominent at the Equator.

However, there are other theories about the shape of the Earth. Some people believe that it is a triaxial ellipsoid or that the Earth is actually a geoid.

That said, the term sphere is used as a broader definition of its shape. But if the waters that fill the oceanic plates are removed, saying it's a geoid might be more appropriate.

What determines the shape of the Earth?

Although the oblate spheroid is the closest shape to the actual shape of the Earth, our planet is not a perfect oblate spheroid.

This is because the mass is not evenly distributed within the planet. The more there is a concentration of mass, the greater its gravitational force, creating bumps around the globe.

The shape of the planet also changes over time due to a combination of other dynamic factors. The mass moves around the interior of the Earth, altering these gravitational anomalies.

For example, mountains and valleys are created and disappear due to plate tectonics. Other times meteorites create craters on the surface.

Additionally, the gravitational pull of the Moon and Sun not only cause oceanic and atmospheric tides, they also cause land tides. The changing weight of the oceans and the atmosphere can also cause deformations in the crust.

To balance the unbalanced distribution of mass on Earth and stabilize its rotation, the entire surface of the planet rotates and tries to redistribute its mass evenly along the equator.

To monitor the actual shape of the planet, scientists have several methods at their disposal.

For example, GPS systems can detect changes in surface elevation. They also have laser satellites, specialized telescopes, and other technologies.

History

Long before Christopher Columbus sailed the oceans, Aristotle and other ancient Greek scholars proposed that the Earth was round.

This was based on a number of observations, such as the fact that the boats not only appeared smaller as they moved away, but also appeared to sink to the horizon. This was to be expected if one was navigating through a ball.

But Isaac Newton was the first person to propose that the Earth was not perfectly round. Instead, Newton suggested that it was an oblate steroid. An oblate sphere is a sphere that is flattened at its poles and is swollen at the equator.

Newton was correct, and because of this bulge, the distance from the center of the Earth to sea level is about 21 km wider at the Equator than at the poles.

Our planet is not like a metal top; rather it has a plasticity that allows its shape to deform a bit.

Oblate Spheroid

An oblate spheroid is the shape that is obtained after rotating an ellipsis around its minor axis. Because of this, if a cross section of the Earth was taken that contains a polar axis, the shape obtained would also be an ellipsis. The polar would be its minor axis, and the equatorial axis would be its major axis.

However, if you were to take a cross section through the Equator, or any plane parallel to the Equator, you would get a circle.

Implications for its shape

Since the Earth is a sphere, the surface receives more intense sunlight (and more heat) at the Equator than at the poles. At the equinox, due to the position of the sun, the poles receive about half as much solar intensity as that region.

At the poles, the sun appears to be located on the horizon for periods of up to 24 hours, and its rays spread horizontally over the surface.

During the year, a location in a temperate zone can enjoy tropical heat in the summer and arctic cold in the winter.

The distribution of heat around the planet, and throughout the year, together with the physical properties of the air produce a distinctive pattern of climate zones.

The sun heats the surface of the soil or the sea more intensely in the tropical zone. The heated air rises and as it cools it releases its moisture as rain, creating the regions of the planet where it rains the most.

This air from the tropics reacts with the air coming down from the poles and settles down. Here the air is compressed, heated and absorbs moisture. It is at this latitude where Earth's desert belts meet.

Other theories about the shape of the Earth

Some people believe that according to the real shape of the Equator, depending on whether it is a circle or an ellipsis, the shape of the Earth would change. If it is an ellipsis, then the ellipsoid would be triaxial instead of rotational.

Another theory says that the South Pole is a vacuum, accompanied by a higher level around the same level at the North Pole. This would imply that the northernmost latitudes would be flatter, while the southern latitudes would be more pronounced.

A third theory states that the actual shape of the Earth is more like a geoid; it is usually used for scientific measurements.

This mode of representation uses mean water levels as the primary way to mark a precise vertical point in a location.

References

1. The spherical shape of the earth. Recovered from sealevel.jpl.nasa.gov
2. What is the real shape of the earth? Recovered from techinabottle.wordpres.com
3. What is the shape of the earth? (2009). Recovered from johndcook.com
4. Strange but true: earth is not around (2007). Recovered from scientificamerican.com
5. What is earth? (2017). Recovered from nasa.gov