Earth - the only known planet in the universe where life exists.Its age is estimated about 3.5-4.5 billion years.
For millennia, people imagined the Earth as the plane, mounted on a support.And such an idea existed for many centuries and in different nations of the world.However, navigation, military long trips, shopping expeditions gave food for thought for the inquisitive mind.
the first time on earth as a sphere of ancient Greek scientists have suggested.In the 3rd century BC(235 BC) Erastofen (geographer and astronomer) Determine the diameter of planet Earth by the Sun at a certain point, located near the city of Alexandria.This city - center of science and culture of ancient Egypt.Archaeological materials, studies of modern Egyptologists suggest that in the 3rd millennium BCEgyptians had a very good idea of the universe and the earth.
the summer solstice (in the modern calendar June 22) Erastofen calculated the angle of incidence of sunlight and shadow of the obelisk.The data allowed him to determine the radius of the Earth.In the 2nd century BCPtolemy tried to calculate the circumference of the planet in a similar way.
astronomers of antiquity came from the geocentric theory postulates - all the visible celestial bodies moving around the earth.In the Middle Ages (9-11 cc.) Central Asian scientists also conducted measurement studies.They analyzed the works of ancient scholars.The diameter of the Earth calculated and Indian scientists.The studies were conducted in different ways, in different parts of the globe and in different units.Nevertheless, the results of calculations of the parameters of our planet, the sun, the moon was close in value.
In the 16th century, the positions of supporters of the heliocentric structure of the universe.The sun - the center around which the planets, including our Earth is not the largest.
interaction of the planet to the Sun, the Moon and the other planets of the universe is undeniable.It is assumed that the Earth and the Moon once constituted a single entity.But, faced with a huge asteroid billions of years ago, the Moon became a separate cosmic body.Turnover of it around our planet is 27 days and almost 7 hours - this is our Earth Month.And the time in which the earth turns around the sun - 365 days - Earth year.
course, that there were errors in the centuries-old measuring parameters of our planet, today officially recognized the following dimensions: the radius of the Earth - 6378.1363 km;the diameter of the Earth at the equator - 12756, 274 km;the diameter of the South to the North Pole - 12514 km.
Actually, speaking about the parameters of the planet, it is more logical to talk about its diameter, since the Earth is not a perfect sphere, the force of rotation makes it an ellipse or geoid.It is easy to calculate the difference between the values of 43 km, and the average diameter of the Earth - 12,743.2 km.
How accurate are these numbers?Measuring and verifying the parameters of the Earth continues.Modern scientists work in international teams, that allows to get information from different points of the globe.In 2007, we published the results of measurements, which showed that in comparison with the year 2000, the Earth's diameter has decreased by 5 millimeters.Does this mean that our planet is decreasing?Rather, it is evidence that improved methods of measurement used by more complete and accurate information, modern geophysical models.
Thus, the average diameter of the Earth according to the latest updated figures - 12 756 274 km.
In modern studies use three basic methods:
- measurement of radio waves (quasars), which take 70 radio telescopes located in different parts of our planet.
- satellite laser ranging, when the distance from the spacecraft to the ground is measured with a laser.
- Research program of satellite systems GPS and DORIS.
