We can independently find out when a certain event occurred or in what year a certain device was invented - for this people have publicly available information about the last thousand years, calendars and relatively accurate dates. However, there are also those things whose age can only be accurately determined by scientists who use effective methods to establish the age and era when they occurred. The exact age of those artifacts that could exist for many tens of thousands of years before the appearance of man and even their ancestors is determined!
Geochronology
In each of the geological periods of the Earth, there were living organisms and fossils appeared, formed by a unique climate. The method of determining the age of the fossil in the geochronological annals is similar to the principle of operation of the Chinese calendar, only instead of a year - era. If an archaeologist is able to detect a fossil, he will be able to determine at what stage of the planet's development this artifact originated.
To establish the age of the fossil, its characteristics and structure will be studied to understand for which period the properties of the fossil are characteristic: an artifact from the past can belong to only one era. Its distinctive features will be similar to other representatives of the fossilized flora and fauna from that segment of the planet's life. Such fossils are called guiding and become the main representatives of their era. To become a leading, a fossil must meet many requirements: the fossil must often be found in wide search areas, have recognizable features and a narrow period of existence.
A similar method was used in 2014, when scientists from Kazakhstan were poisoned on an expedition to the Shiderty River. The river is located on the territory of the steppe, and on its banks lies limestone and stones. Archaeologists took up the study of the stones and determined that they were fossilized mollusks of the ancient species of brachypods: these are invertebrates that lived in a marine environment, and were found in the steppes. The find once again confirmed that in the Devonian period on the site of the steppe was the Tethys Ocean.
Gyrochronology and Spectral Analysis
This method determines the age of stars that are hundreds of light years from the solar system. The aging of cosmic luminaries does not occur evenly - 90% of the time of their existence they almost do not change, and serious metamorphoses begin to occur in the last episodes of existence. If a person grew up to 5 years, did not change all his life and only in the 90th year began to age sharply, at the age of 91 he died, his life would be similar to the model of the existence of stars in space.
Astronomers at first could not determine even the approximate age of stars that are not in the last stages of existence. Scientists have begun to study how a star emits light. The sun, for example, emits a rainbow with thin lines of black color, if you decompose the spectrum of the glow. The lines are engaged in the absorption of various chemical elements, and from them it is possible to determine what the composition of the star is. With the help of the composition of luminaries, scientists have learned to determine their age. In stars, the process of thermonuclear reaction is constantly taking place, during which hydrogen burns and helium appears. The less helium and the more hydrogen, the younger the star.
Also, an old star from a young one can be distinguished by the speed of its rotation. New stars rotate around their axis at a higher speed. But to observe the rotation, ultrasensitive telescopes are needed, through which landmarks are set - sunspots. The older the star, the more such spots, and it becomes more difficult to observe its rotation.
The telescope that is able to observe the rotation of the stars is Kepler , a device that has detected thousands of exoplanets and stars. With the help of a telescope, it was possible to confirm that the formula of gyrochronology works, and scientists can calculate the age of stars, knowing the speed of their rotation. However, there are events due to which the calculations may be inaccurate - for example, the weakening of the magnetic field: as a result of this process, the star begins to rotate faster.
Howart epigenetic clock
When using this method, scientists turn to cells whose DNA chains store age markers characteristic of their eras.
The age of the cells is established by looking at their DNA. When a cell during formation determines whether it will be a vessel cell or a neuron, unnecessary genes are "washed out" of its composition, collected in tangles and methylated - frozen and do not affect the work. Sections of the DNA chain that have undergone methylation are glued to each other. The greater the age of the cell, the more such sections of DNA in it.
Scientist Steve Howarth learned to determine the exact age of a person by looking at his DNA cells. He studied different parts of the chains for 4 years and derived a clock that allows to determine human age more accurately from the methylation pattern than other signs of maturation and aging.
For the first time , Howart watches began to be used in Europe when determining the exact age of immigrants. When undocumented refugees are screened, their ages need to be clarified. Previously, this was done either by eye, or simply asked from the migrants themselves. It is more profitable for guests of the country to call themselves minors, because in this way they received more rights and benefits, and in the case of crimes, the law would not be so harsh on them.
However, the use of Howart watches faced criticism, because the technology is far from perfect. The cells chosen for study can age not only from the passage of time, but also from stress, illness or toxin poisoning. After the harmful effects, the cell can become decrepit and cease to be useful to the body, although its carrier may be only 10 years old.
Dendrochronology
This method was taught to us in school, in the lessons of natural history or biology. We will talk about annual rings on trees - a pattern formed by changes in climate. The pattern remains on wooden houses and objects, so you can accurately find out their age.
In summer, the tree grows faster than in winter, so many rings of dark and light shades can be found on the sawing of the tree. Light stripes are the warm season when the tree grew quickly, and dark and narrow stripes appeared in winters, when the plant slowed down its development due to an unfavorable climate. In a year, a tree adds one ring, so it is possible to determine its exact age or the climate change to which it was exposed.
The method was used in Veliky Novgorod, when they tried to determine the exact age of wooden bridges. They paved the streets at that time soundly, used the principle of laying thick logs on thin ones. The design was updated about once every 15-20 years, and new ones were laid on the old logs on the principle of a layer cake. In other places of the city, the pavements consisted of as many as 28 layers of logs, the first of which were installed many centuries ago.
