the Age of the Earth so is great that he is difficult for imagining to itself. But if to assume that to our planet only one year the mankind has existed less than five hours.
The Mankind tried to define centuries age of the Earth. In the beginning of a XVII-th century archbishop Army James Asher has calculated date of creation of the world under the Bible. It has defined it as 4004 year BC, this chronology can be found in old editions of the Bible.
Now we know that Asher was mistaken - more than a million times! For today the age of the Earth accepted by scientists makes 4600 million years. It approximately same, as well as age of the Sun and other planets.
In the end of a XVII-th century the Danish doctor and scientist Nikolaus Steno (which in due course too became the bishop) has concluded "Age of the Earth" that the top layers of sedimentary breeds collecting under water, more youngly, than bottom. In a XIX-th century this opening has helped scientists to develop relative chronology of breeds and, thus, partially to define age structure of the Earth. The science about dating of breeds is known under the name geochronology. However only in the XX-th century beginning the British and American scientists have found out that some radioactive elements can be used as "ёрё№" for fixing of the huge periods of time. Atoms of these elements decay in due course, forming other elements. So, for example, after enough long period uranium turns to lead, radiating thus radiation.
Nine heavy elements, meeting in a natural kind, including rady and uranium, are radioactive. The same concerns some isotopes (versions of the same elements, atoms different by weight) easy elements, such as rubidium and strontium.
Scientists have opened hours, but did not know how to define on them time. With it they were helped by creation during time and after the device Second World War under the name a mass spectrometer. It divides atoms on their weights and electric charges and allows to define minute quantities of radioactive substances in breeds.
Radioactive substances break up with certain speed. Unit of its measurement is the half-life period - time for which half of initial quantity of radioactive substance breaks up. The second half-life period is a half of remained substance and so each time this period decreases.
The Most known method of dating is dating on radio carbon with which help it is possible to define age of any organic substance which have reached us from the past (such as bones or wood). So, for example, this method have applied in 1988 to dating of the Turin Shroud in which as believe, in due time have turned Jesus Christ. However to date on radio carbon inorganic breeds it is impossible, other methods are for this purpose applied. They include disintegration with transformation of a radioactive isotope kalija in radioactive argon, disintegration of a radioactive isotope of rubidium in radioactive strontium, and disintegration of uranium and thorium with transformation into lead.
Acknowledgement of age of the Earth has come from space. Some fallen to the ground meteorites contain a mineral under the name troilit. In it it is not enough or absolutely there is no uranium, therefore believe that the lead found in it represents its initial quantity on planets, including the Earth. Thus, it was possible to check up correctness dating uranium-lead. Also the lunar breeds delivered to the Earth by the American astronauts in 1970th years have been analysed. From these breeds and samples of meteorites the data about age of the Moon and the meteorites, similar themes on which defined age of the Earth is obtained.
Traces of a primitive life are found out in breeds, which almost 3,5 billion years, - oldest of known breeds on the Earth. This life is presented by bacteria and seaweed, i.e. The elementary unicells.
Possibly, throughout previous 1000 million years on the Earth oceans gradually were formed of water of the cloak which are thrown out by volcanoes on a surface at eruption. Originally atmosphere consisted, obviously, mainly from hydrogen. Oxygen in air was formed or as a result of light influence on water steams, or it allocated rastenievidnye sea organisms.
About 570 million years ago on the Earth life rapid development has begun. About 400 million years ago in atmosphere already was enough oxygen for growth of plants on a land, and for the subsequent 50 million years have appeared and land animals have started to evolve.
Geologists divide history of last 570 million years into a number of the periods. Earliest of them is called as cambrian. Geological time from the beginning kembrija (590 million years ago) to present chetvertichnogo the period is known as fanerozojsky eon. Other part of history of the Earth usually unites under the general name dokembry. If to imagine that the Earth exists one year, that early forms of a life have appeared in the beginning of May, and the cambrian period has begun in November. The first people have arisen about 7 o'clock in the evening on December, 31st, and the modern person was generated approximately for five minutes till midnight.