Radius Of Earth

And so, how could calculate the radius of such a huge object, like Earth, if at the time and distance to a nearby town found it difficult to calculate. Lived in those days in Alexandria, Greek mathematician, astronomer, geographer and poet Erastofen. At the head of which came a brilliant idea.

He noted that in the city of Siena, which is located on the same meridian of Alexandria in the afternoon sun solstice sunbeam finishes to the bottom of the deepest wells. Hence, while the sun is directly overhead. And then he was at the same time in Alexandria, with a big bowl with an arrow in the middle of and magnitude of the shadow of this arrow and calculated how many high sun) measured arc length along the meridian between Siena and Alexandria, it was 7 degrees 12 minutes. At the same time he knew the distance between these cities, it was 5000 steps.

After these calculations are not difficult to know how many stages counts 1 degree and, respectively, as on 360. Erastofen calculated that the length of the meridian 250 000 stages, is already going for more modern units - is 39,500 km and the radius of earth - 6,290 km. According to the calculations of modern astronomers, the length of the meridian 40000 km, and the range - 6,378 km.

So that we can only imagine what the minds of living in those times, and how exactly to calculate such values, while not having any modern technology.

Kerensky Eratosthenes (276 BC. E. - 194 BC. Er.) - The Greek mathematician, astronomer, geographer and poet. From an early age, he lived in Alexandria, and here he was educated under the guidance of his fellow citizen scholar Callimachus, who was standing at the head of the Alexandrian library.

 
Dissatisfied with the knowledge acquired in Alexandria, Eratosthenes went to Athens, where so closely approached the school of Plato, which is commonly called he a Platonist. The result of the science in these two centers of Greek education was very versatile, almost encyclopedic erudition Eratosthenes, he wrote, except for works on mathematics, astronomy, geodesy, geography and history, yet the treatise "On Good and Evil", the comedy, etc.

 
King Ptolemy III Ever get immediately after the death of Callimachus called Eratosthenes in Athens and charged him superintendence of the great Alexandrian library. Erastofen - author of many works on mathematics, astronomy, geodesy, and geography.

 
One of the interesting facts of life of Eratosthenes - calculation of the radius of the Earth.

 
The ancient Egyptians noticed that during the summer solstice sun illuminates the bottom of deep wells in Siena (now Aswan) and Alexandria - no. Eratosthenes used this fact to measure the circumference and radius of the Earth.

After measuring the angle was 7 degrees 12 minutes, ie 1 / 50 of a circle. So Siena separated from Alexandria on 1 / 50 the circumference of the Earth. Distance between cities was considered equal to 5.000 stages; hence, the Earth's circumference was equal to 250.000 stages, and then the radius of 39.790 stadia.

It is unknown what stage of Eratosthenes used. If Greek (178 meters), its radius was equal to 7.082 km of land, if the Egyptian, the 6.287 km. Current measurements yield for the average Earth's radius value 6.371 km.

Today we know that the Earth's crust is surrounded, which consists of a rock. The Earth's mantle is the change in the outer part of the mantle, a liquid rock, when the poet down on the Earth's core. The core consists of two parts, the outer and inner core, and is often the material of iron. The inner core is probably similar to the temperature at the surface of the Sun. Let's look on the radius of earth.

Our continents and oceans in the outermost layer of the Earth's crust. Compared to the radius of the Earth (median where the radius of earth is 6370 km), is the Earth's crust is very thin. Under the sea to measure the thickness of the Earth's crust between 8 and 15 km. due to the continents reached Interior 30-100 miles.

The name of its discoverer or Mohorovi short interruption between the crust and upper mantle, a prominent border mould. Analyzing seismological data to Mohorovi in this special place seismic velocity of travel of any significant changes, which also means that waves, as a material in the Earth's core.

In comparison with the bark of the sea is the structure of the continental crust, very varied soils and stronger. It contains rocks up to 3.8 million years ago. Increases the effects of wind erosion, deformation, and the reduction of many different layers. The surface is often formed by sediments and volcanic rocks, which have a very low population density.

On the other hand, the structure of the Earth's crust in the ocean, relatively simple. It consists of a smaller number of layers. First and foremost is a measurement of the sound of a few hundred meters of sediment, up to three kilometers. Among them is a layer of sediment, which consists of hard rock, particularly basalt and a small mix of sedimentary rocks. This layer is a measure of the average one and a half kilometers.

The mantle beneath the Earth's crust of the Earth is approximately 82% of the volume and 67 per cent of the total mass of the Earth. Seismic waves and volcanic deposits contain information on the composition. Based on physical characteristics, is that we are relatively fresh from the mantle is divided into upper and lower layers. In the same way, what happens in the Earth's crust, sign up here, too, has changed between the seismic waves. These changes in a particular area, in the 100-200 kilometers deep. This region is the area of Gutenberg. It is possible that the cause of the deviation of the flow of stars within the world of waves.

The Earth's crust and the upper part of the Earth's surface to the mantle Gutenberg area, form the Lithosphere. Asthenosphere, which is solid, less is below. Lithosphere and Asthenosphere is interactive. When putting the material in the Asthenosphere at the ridge in the ocean, the Lithosphere.

There is relatively little is known about the Earth's core. Seismic waves in kernel penetrate or distracted is just one part of it. During its internal part, with a diameter of 2,400 kilometers of solid iron and nickel, the outer core, which is 2,300 miles of thick, cast iron and nickel. Calculations of the Earth's core, its density is four times greater than the density of the Earth's crust.