Diameter of the Earth

Earth is the only known planet in the universe on which life exists. Its age ranges from about 3.5-4.5 billion years.

For many millennia, man represented the Earth as a plane set on a support. And this idea existed for many centuries and for different peoples of the world. But sailing, military long trips, trade expeditions gave food for thought to an inquisitive mind.

For the first time, Greek scientists have suggested that the Earth was a sphere. In the 3rd century BC. (235 BC) Erastofen (geographer and astronomer) determined the diameter of the planet Earth by the Sun at a certain point, located near the city of Alexandria. This city is the center of science and culture of Ancient Egypt. Archaeological materials, studies of modern Egyptologists indicate that already in the 3rd millennium BC. The Egyptians had a very good idea of the universe and the Earth.

On the day of the summer solstice (according to the modern calendar on June 22), Erastofen calculated the angle of incidence of the sun's rays and the shadow from the obelisk. The data obtained allowed him to determine the radius of the Earth. In the 2nd century BC. Ptolemy tried to calculate the circumference of the planet in a similar way.

Astronomers of antiquity proceeded from the postulates of the geocentric theory - all visible celestial bodies move around the Earth. In the Middle Ages (9-11 centuries), Central Asian scientists also conducted measurement studies. They analyzed the works of ancient scientists. The Earth's diameter was calculated by Indian scientists. The studies were carried out in different ways, at different points of the globe and in different units of measurement. Nevertheless, the results of calculations of the parameters of our planet, the Sun, the Moon were close in meaning.

In the 16th century, the positions of supporters of the heliocentric structure of the universe were strengthened . The sun is the center around which the planets revolve, among which our Earth is by no means the largest.

The interaction of our planet with the Sun, the Moon and other planets of the universe is undeniable. It is assumed that the Earth and the Moon once formed a single whole. But, faced with a huge asteroid billions of years ago, the Moon became a separate cosmic body. Turning it around our planet is 27 days and almost 7 hours is our earthly month. And the time for which the Earth turns around the Sun - 365 days - the Earth year.

Naturally, there have been errors in the centuries-old dimensions of the parameters of our planet, today the following dimensions are officially recognized: the Earth's radius is 6378.1336 km; The Earth's diameter along the equator is 12756, 274 km; Diameter from the South to the North Pole - 12,514 km.

Actually, speaking about the parameters of the planet, it is more logical to speak about its diameters, since the Earth is not an ideal ball, the force of rotation makes it an ellipse or a geoid. It is easy to calculate that the difference between the values is 43 km, and the average diameter of the Earth is 12743.2 km.

How accurate are these numbers? Measurements and refinements of the Earth's parameters continue. Modern scientists work in international teams, which allows you to get information from different points of the globe. In 2007, the results of measurements were published, which showed that in comparison with 2000, the diameter of the Earth decreased by 5 millimeters. Does this mean that our planet is decreasing? Rather, it is evidence that the methods of measurement are being improved, more complete and accurate information is used, and modern geophysical models are used.

Thus, the average diameter of the Earth according to the latest refined data is 12 756, 274 km.

In modern studies, three main methods are used:

1. Measurement of radio waves (quasars), which receive 70 radio telescopes located at different points of our planet.
2. Satellite laser ranging, when the distance from the spacecraft to the surface of the earth is measured by a laser.
3. Research programs of satellite GPS systems and DORIS.