بحث عن الذهب بالانجليزي

تعبير انجليزي عن الذهب بحث عن الذهب بالانجليزي معلومات عن الذهب بالانجليزي تعبير عن الذهب موضوع بالانجليزي عن معدن الذهب مقالة عن الذهب البرزنتيش تعبير انجليزي عن gold بحث عن الذهب بالانجليزي تعبير عن الذهب بالانجليزي معلومات عن الذهب بالانجليزي كلمة ذهب بالانجليزي معنى كلمة ذهبت بالانجليزي ترجمة  golden ترجمة كلمة ذهب بالانجليزي معنى كلمة الذهب بالانجليزي ماذا تعرف عن الذهب..ومصطلحاته تقرير عن الذهب بالانجليزي

gold

gold

Element 79, gold is an unalterable precious metal much sought after since the dawn of time.

Pure gold is a noble metal, the most malleable and ductile of known metals, it is both dense and tender.

The quantity of gold extracted by man is estimated, at the end of 2008, at 163 kilotonnes, a small cube of about twenty meters. In 2010, gold reserves were estimated at 51 kilotonnes. China is in the forefront with 13.8% of world production in 2010, ahead of Australia with 10.2%, the United States, 9.2%, Russia, 7.6%, Africa South, 7.6% and Peru, 6.8%.

Where does the gold from the Earth come from?

Gold is made in the stars like all the elements of matter found on Earth.

Stars are nuclear reactors whose fuel will evolve during its life cycle. When the nuclear reaction races, the heart of the star contracts, the temperature rises and the nuclear reactions restart, with a new fuel. Thus the life of a star is a succession of gravitational contractions and cycles of nuclear combustion.

Hydrogen is the most abundant element in the known Universe, in fact, it represents 75% of the total mass and 92% of the total atoms of matter. It is the main constituent of stars, gas planets, nebulae and interstellar gas. Every second, the stars convert millions of tons of hydrogen (H) into energy, via nuclear fusion that combines nuclei of hydrogen to form helium nuclei (He).

The star then burns slowly, economically and lasts billions of years. Helium is the second constituent of the universe. When they have burned all their reserves of hydrogen, the stars collapse, which increases their internal temperature, and continue their combustion by transforming helium into carbon (C), at this stage it is called 'flash of light'. 'helium'. Then the carbon is transformed into nitrogen (N), nitrogen into oxygen (O). Silicon oxygen (Si).

The elements produced in a combustion cycle serve as fuel for the next cycle. As time goes by, the combustion cycles are shorter and shorter because the fuel becomes less and less energetic. These are the most massive stars that will make all the chemical elements up to number 26, ie iron (Fe), the most stable element of the list of known elements. Then they will get fat, exhaust all the gases contained in their core and the upper layers will cool down.

This sequence will cause an explosion of the upper layers, and their projection in the interstellar space. This is how we find in the nebulae, the first elements, up to iron. And gold?

To see the gold appear, it will be necessary to wait for a cataclysmic cosmic event, a gigantic explosion, that of a supernova.

A supernova thus appears as a new star, seen from the Earth, hence its name, nova. But in reality this explosion of the massive star, results in its total destruction. It is during its explosion in supernova, that the star releases the chemical elements, which it synthesized during its existence and during the explosion itself. This cosmic event occurs only with stars much larger than our Sun, between 1.5 and 5 times its mass.

The violent agony of the star causes a terrible explosive collapse. Its radius narrows to 10 km, its final density is enormous, the nuclei of the elements can not resist and the heart explodes, projecting the upper layers of the star into space.

This is how other heavier elements will appear, beyond element 26 (iron), such as cobalt, nickel, copper, zinc, gallium, etc.

And gold?

Above 5 times the mass of the Sun, the collapse of the star is even more violent. The nuclear reaction can no longer be stopped. The heart of the star becomes a black hole.

As in the previous case a gigantic explosion, will project the upper layers of the star in space, over hundreds of billions of km, sowing the interstellar medium of even heavier elements, such as platinum, gold, mercury, lead, uranium, plutonium ...

These heavy elements are distributed in very small quantities, in gas and dust nebulae.

Other cosmic events cause the creation of heavy elements such as gold, especially the collision or fusion of two neutron stars.

All these elements will be found in the solar systems and therefore in the planets. It is in the nucleus of the Earth that there is the most gold, billions of tons, but the gold is rare in the earth's crust, in spite of everything one finds "many" and it is well distributed on the surface of the Earth.

The distribution of gold on Earth would be 0.004 mg of gold per cubic meter of material.

Studies show that the concentration of the earth's crust is between a hundred and a thousand times too high, compared to the original nebula.

A numerical simulation carried out in 2011 made it possible to explain the abundance of gold on the Earth's surface.

The gold found on the surface of the Earth comes from the great late bombardment that took place 3.8 billion years ago, at a time when billions of meteorites were bombarding the Earth.