The Earth, our blue planet, has been the object of study and curiosity since time immemorial. One of the fundamental challenges for humanity has been to locate, divide, and understand its vast surface. To this end, civilizations created reference systems that allowed any point on the globe to be precisely located. These systems include meridians and parallels, imaginary lines that have gone from being a mathematical abstraction to a basic tool for navigation, cartography and modern daily life.
In this context, meridians They have a special relevance, since their influence goes far beyond the simple location of sites on a map. They have played an essential role in the geographical division of the Earth into North, South, East and West, as well as in the organization of time, time zones, and the development of international trade. Understanding how meridians work and their relationship to the division of the planet is fundamental for students, teachers, and anyone interested in understanding how our world works.
What are meridians and how do they differ from parallels?
The globe is segmented by a network of imaginary lines which facilitate the location of specific points on its surface. These lines, called meridians y parallels, constitute the basis of the geographic coordinate system. Although both types of lines are essential, they perform different functions and present specific characteristics.
- Meridians: Its vertical lines extending from the North Pole to the South Pole. Each meridian is a semicircle and they all converge at the poles. The prime meridian It is Greenwich (0°), which divides the Earth into two large halves: the eastern and western hemispheres.
- Parallels: Its horizontal lines that surround the Earth in an east-west direction. Their reference line is the Ecuador (0°), which separates the planet into the Northern and Southern Hemispheres. Other important parallels are the Tropics of Cancer and Capricorn, and the Arctic and Antarctic Circles.
While the parallels allow to calculate the latitude —the distance of any point from the Equator—, the meridians allow to determine the length —the distance from the Greenwich Meridian—. The combination of both geographic data allows us to locate any location on the planet.
The origin and historical importance of the meridians
The concept of meridian It comes from the Latin meridies, meaning midday: the instant when the sun reaches its highest point in the sky and crosses the imaginary line of the local meridian. This information not only served as a guide before the existence of precise clocks, but was also fundamental for measuring and establishing time in different parts of the world.
Throughout history, different peoples chose different locations for the prime meridian, also known as the zero meridian, generating some confusion and lack of uniformity in navigation and trade. It was in the 19th century, with the International Meridian Conference of 1884 in Washington, D.C., when representatives from 26 countries officially agreed that the Greenwich Meridian (0° longitude) would be the universal reference point. This agreement was driven by the need to unify growing international trade and facilitate intercontinental travel.
Division of the Earth: North, South, East and West
The influence of meridians y parallels It is evident in the way we have divided the planet:
- Northern Hemisphere and Southern Hemisphere: El Ecuador It is the reference line that delimits both hemispheres. The territories to the north belong to the Northern Hemisphere, and those to the south belong to the Southern Hemisphere.
- Eastern (East) and Western (West) Hemisphere: El Greenwich Meridian It separates the Earth into the eastern and western hemispheres: to the east, we find Asia, Oceania and much of Europe and Africa; to the west, America and the Atlantic.
Each meridian represents a different angle in degrees, from 0° (Greenwich) to 180°, which is the antimeridian located on the opposite side of the Earth and approximately coinciding with the international date lineThus, the meridian system is the fundamental tool for differentiating between East and West, while the parallels do the same for North and South.
What are meridians and parallels used for today?
The use of meridians and parallels is not exclusive to classical cartography. Currently, They constitute the framework on which geospatial technology and location services are based.. Thanks to these systems, we can obtain precise coordinates in real time for different applications.
- Geographic coordinates: The intersection between a meridian and a parallel provides a exact location on the Earth's surface, which is essential for modern navigation and positioning systems.
- Time zones: The meridians They serve to divide the Earth into 24 time zones of approximately 15° each. This allows the time to be adjusted according to the geographical position, facilitating international trade and communication.
- GPS Navigation and Geographic Information Systems (GIS): These systems use coordinates derived from meridians and parallels to provide precise locations, map phenomena, and plan projects in various fields.
- Mapping and daily mobility: Digital maps and navigation apps use these lines to help users plan routes, locate locations, and understand climate zones.
Main characteristics of the meridians
The meridians They present several properties and characteristics that make them essential for the division of the planet:
- They are semicircles that connect the North Pole and the South Pole.
- The Greenwich Meridian It is the universal reference for longitude 0°.
- El antimeridian (180°) coincides with the International Date Line.
- Each meridian is separated from the next by one degree (or fractions), facilitating a regular segmentation of the planet.
- La posición of a point on Earth is determined by the intersection of a meridian and a parallel.
In addition, meridians have been key in the design of the time zones, which allow for global time synchronization, especially following the expansion of railways and international courier services.
Main parallels and their influence on the division of the Earth
Amongst the parallels The most notable ones are the Ecuador (0°), the Tropics of Cancer and Capricorn (23,5° north and south respectively) and the Arctic and Antarctic circles (66,5° north and south). These lines not only delimit hemispheres, but also mark climatic zones, limits of solar incidence, and phenomena such as the midnight sun and polar night.
- Ecuador: It is the line that divides the Earth into the northern and southern hemispheres, located at 0°.
- Tropics of Cancer and Capricorn: They are located approximately at 23,5° north and south, marking the limits of the tropical zones.
- Polar circles: The Arctic and Antarctic, located at 66,5°, delimit the areas where the sun can remain visible or absent for long periods.
Latitude and longitude: the geographic coordinate system
La latitude indicates the angular distance of a point from the Equator and It is measured in degrees from 0° to 90°, north or south. The length It is measured from the Greenwich meridian (0°) to 180° east or west. Both are expressed in degrees, minutes and seconds.
For example, Oslo is approximately 60° north latitude and 10° east longitude, while Panama is located at 8° north latitude and 80° west longitude. Thanks to these measurements, any location can be precisely located, facilitating navigation and exploration.
The impact of meridians on everyday life
The influence of meridians and parallels transcend the geographical scope. Thanks to them, our clocks are synchronized worldwide, international trade is organized, and maritime and air navigation can be carried out with greater safety and efficiency.
- Organization of time: Local time depends on the meridian of each location. The adoption of time zones allowed for the unification and simplification of international timetables, improving coordination in transportation and communication.
- International transactions: The use of the Greenwich Meridian as a global reference point helped standardize time and facilitate global trade and diplomacy.
- Navigation and exploration: The precise measurement of longitude, based on meridians, enabled great advances in exploration and the expansion of maritime and land trade.
The Greenwich Meridian: Origin and Relevance
El Greenwich Meridian It was adopted as a universal reference in the International Meridian Conference of 1884At that time, the more than 70% Most of the world's trade used maps based on Greenwich Mean Time, and the United States had already implemented it as the basis for its time zone system. Designating Greenwich as longitude 0° facilitated the standardization of measurements and boosted international trade.
Since then, the Greenwich Meridian It is the reference for measuring longitude and establishing time zones around the world. Its antimeridian, at 180°, marks the international date line, which determines when each day begins and ends.
Curiosities and modern applications of the meridians
- Geodetic meridian and astronomical meridian: The location of the prime meridian has evolved with technical improvements and systems such as the World Geodetic System 84 (WGS84)Currently, it is determined by GPS, but the historic line remains a tourist attraction.
- Magnetic meridian: In addition to the geographic meridian, there is the magnetic meridian, which connects the Earth's magnetic poles and is used in compass navigation, although it has differences due to the magnetic declination.
- Technology and digital maps: Platforms like Google Maps use meridian and parallel coordinates to provide precise guidance and geospatial analysis of diverse phenomena in our environment.
To better understand how these systems work, there are interactive resources, activities, and videos that make it easier to visualize how they divide the Earth and allow you to precisely locate locations. Practice with maps, simulations, and reflective questions helps consolidate this knowledge and appreciate its relevance in everyday life.
