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To obtain information about the Earth, studies are carried out from the perspectives of different disciplines. For example, geodesy is one of the branches of science that is responsible for measuring the size of the Earth and calculating other related data.
Geodesy and the measurement of the Earth
Geodesy, using different scientific methods, ensures that the size and shape of the Earth are accurately analyzed. Throughout history, and especially when the first scientists tried to determine the size and shape of the Earth, geodesy played an important role in scientific knowledge.
It is believed that one of the pioneers in determining the size of the Earth was the great philosopher and scientist Aristotle. Later, the Greek philosopher Eratosthenes was also able to estimate the circumference of the Earth. His calculation was 40,233.6 kilometers, just slightly more than the currently accepted measurement.
Methods for measuring the size and shape of the Earth
To study the Earth, geodesy includes concepts such as ellipsoids, geoids, and datums. An ellipsoid is a theoretical mathematical model that shows a simple representation of the Earth’s surface. It is used to measure distances on the surface without having to include elevation changes and other landforms.
To get a more realistic version of the Earth’s surface, geodesists use the geoid , which is constructed using mean sea level and does take elevation changes into account.
Another of the most important methods used by geodesy to measure the Earth is the datum . These are data sets that function as reference points for studying global topography. For example, there are two main datums used for transportation and navigation in many countries. These datums are also part of the National Spatial Reference System.
Today, technological advances such as geodetic satellites and global positioning systems (GPS) allow geodesists to make extremely precise measurements of the Earth’s surface. In fact, the data obtained is so precise that it allows navigation around the world. They even make it possible to measure small changes of up to a few centimeters in the Earth’s surface.
the shape of the earth
The Earth has a spheroid or ellipsoid shape , slightly flattened at the poles. It is not in the shape of a perfect sphere. Therefore, its circumference and diameter are different depending on the measurement points. That is, instead of having the same circumference at all its points, the poles are flattened and there is a more bulging area at the equator. In that equatorial zone the circumference and diameter are greater.
The bulge on Earth’s equator measures 42.72 kilometers and is due to gravity and the planet’s rotation. Gravity causes planets and other celestial bodies to contract and form a sphere. In this way, all the mass of an object is attracted towards the center of gravity. In the case of the Earth, the center of gravity is its core, that is, the inner central area of the Earth.
As the Earth carries out rotational movements, the centrifugal force that is produced from these movements modifies the shape of the sphere. This force causes objects to move away from the center of gravity. Therefore, as the Earth rotates, the centrifugal force is greatest at the equator, causing a slight bulge.
The topography of the planet also plays a role in shaping the shape of the Earth, although on a global scale it is almost insignificant. The biggest differences in topography around the world are Mount Everest, which is the highest point above sea level, at 8,850 meters. The lowest point is the Mariana Trench, at 10,924 meters below sea level.
What is the size of the Earth
The Earth is made up of a crust, a mantle, and a core. The Earth’s crust is the thinnest of these layers, while the mantle comprises 84% of the Earth’s volume and extends to about 2,900 kilometers below the surface. However, the Earth’s core gives it the greatest density. It is the only terrestrial planet with a liquid outer core surrounding an extremely dense solid inner core.
To know what the size of the Earth is, it is important to take into account the following measurements:
- The average density of the Earth is 5.515 × 10 kilograms per cubic meter.
- The circumference of the Earth at the equator is 40,075.16 kilometers, and at the poles it is approximately 40,008 kilometers.
- The diameter of the Earth at the poles is 12,713.5 kilometers.
- The diameter at the equator is 12,756.1 kilometers.
- The Earth has an estimated mass of 5.9736 × 10 24 kilograms.
- Its volume is 108,321 × 10 10 cubic kilometers.
- The density of the Earth is 5.515 grams per cubic centimeter.
- The total surface area of the earth is 510,072,000 square kilometers. Of these, 148,940,000 square kilometers are land (about 29.2%) and 361,132,000 square kilometers are water (about 70.8%).
Bibliography
- Sánchez Menéndez, F. Geodesy and Cartography: Concepts and their practical application. (2014). Spain. EOSGIS.
- Zakatov, PS Higher Geodesy Course. (1997). Spain. Rubins 1860.