Our planet is conditionally divided into four hemispheres. How are the boundaries between them? What features do the hemispheres of the earth have?
Equator and Meridian
Planet Earth has the shape of a sphere slightly flattened at the poles - a spheroid. In scientific circles, its shape is usually called a geoid, that is, "similar to the Earth." The surface of the geoid is perpendicular in the direction of gravity at any point.
For convenience, the characteristics of the planet use conventional, or imaginary, lines. One of them is the axis. It passes through the center of the Earth, connecting the upper and lower parts, called the North and South Poles.
Between the poles, at an equal distance from them, is the next imaginary line, which is called the equator. It is horizontal and is a separator on the Southern (all that is below the line) and the Northern (everything that is above the line) hemisphere of the Earth. The length of the equator is just over 40 thousand kilometers.
Another conditional line is Greenwich or zero meridian. This is a vertical line passing through the Greenwich Observatory. Meridian divides the planet into Western and Eastern hemispheres, and is also the starting point for measuring geographical longitude.
The difference between the southern and northern hemispheres
The equator line horizontally divides the planet in half, while crossing several continents. Africa, Eurasia and South America are partially located in two hemispheres at once. The remaining continents are located within one. Thus, Australia and Antarctica are completely located in the southern part, and North America in the north.
The hemispheres of the Earth have other differences. Thanks to the Arctic Ocean at the pole, the climate of the Northern Hemisphere is generally milder than the South, where the land is Antarctica. The seasons in the hemispheres are opposite: winter in the northern part of the planet comes simultaneously with summer in the south.
The difference is observed in the movement of air and water. To the north of the equator, river flows and sea currents deviate to the right (river banks are usually steeper on the right), anticyclones rotate clockwise, and cyclones rotate counterclockwise. To the south of the equator, everything happens exactly the opposite.
Even the starry sky above your head is different. The pattern in each hemisphere is different. The main reference point for the northern part of the Earth is the polar star; in the Southern Hemisphere, the reference point is the Southern Cross. Higher from the equator, land dominates, which is why the majority of people live here. Below the equator, the total number of inhabitants is 10%, since the oceanic part prevails.
Western and Eastern Hemisphere
To the east of the prime meridian is the Eastern Hemisphere of the Earth. Within it is Australia, most of Africa, Eurasia, part of Antarctica. About 82% of the world's population lives here. In the geopolitical and cultural sense, it is called the Old World, as opposed to the New World of the American continents. In the eastern part there is the largest peninsula, a deep gutter and the highest mountain on our planet.
The western hemisphere of the Earth is located west of the Greenwich meridian. It covers North and South America, part of Africa and Eurasia. It completely includes the Atlantic Ocean and most of the Pacific. Here is the longest mountain range in the world, the largest volcano, the driest desert, the highest mountain lake and a full-flowing river. Only 18% of the population lives in the western part of the world.
Date line
As already mentioned, the Greenwich meridian separates the Western and Eastern hemispheres of the Earth. Its continuation is the 180th meridian, which delineates the border on the other side. It is a line of change of dates, it is here that today turns into tomorrow.
On both sides of the meridian, different calendar days are recorded. This is due to the peculiarities of the rotation of the planet. The date line mostly runs across the ocean, but also crosses some islands (Vanua Levu, Taviuni, etc.). In these places, for convenience, the line is shifted along the land border, otherwise the inhabitants of one island would exist at different dates.