The idea of the terrestrial sphere refers to the planet Earth.
In order to know the meaning of the term sphere, it is necessary, first of all, to discover its etymological origin. In this case, we can emphasize that it is a word that derives from Greek, specifically from sphaira , which means "sphere."
The concept is used in geometry to name a body that is limited by a curved surface whose points are equidistant from the center .
What is a sphere
It is a surface of revolution composed of points that are equidistant from the aforementioned center . The union of the spherical surface and the interior constitutes the sphere in question. As a solid of revolution, the sphere is formed by rotating a semicircle around its diameter.
The properties of spheres indicate that all their plane sections are circles . Sections that pass through the center are larger circles , while those that do not pass through the center are smaller circles .
The armillary sphere appears on the flag of Portugal.
The term in astronomy
In the same way, we cannot ignore the existence of what is known as the armillary sphere . Specifically, under that term there is an instrument that has been used since ancient times within the scope of astronomy. Specifically, it was used to determine the position of the different celestial bodies. However, with the passage of time it also began to be used in the field of navigation.
From this device we can highlight another important series of characteristics, among which we can especially highlight the following:
– An armillary sphere is represented on the flag of Portugal . Specifically, it is the yellow part that is responsible for protecting the shield and is included in the flag because it acts as a “wink” to the period of the 15th century in which important discoveries were made by Portuguese navigators.
– If it is called armillary it is because it is made up of several rings or armillaries. Specifically, among these we can highlight the one that is responsible for representing both the meridian and the horizon.
– It is not known who or who were the creators of this article for astronomy, although it is known that its origins are in Ancient Greece.
Other uses of the sphere concept
In the field of watchmaking , the circle in which the clock hands move is called a sphere. The terrestrial or terrestrial sphere , on the other hand, is the planet Earth . The ideal sphere in which the stars apparently move on the Earth is called the celestial sphere .
There are other uses of the notion that are symbolic. The area or context where an individual or an entity exerts influence or acts is known as a sphere. For example: “I never liked the sphere of politics,” “Don't worry, Jorge is a trustworthy man who has been in my sphere for many years,” “The tertiary academies that operate in the province belong to the sphere of politics.” Ministry of Education of the Nation” .