The list of spheres of knowledge which Mendeleevs genius touched upon is enormous: chemistry, physics, earth sciences, metrology, economics, metallurgy and much else. Mendeleevs legacy comprises 25 volumes, a third of them devoted to chemistry.
D.I.Mendeleev, the outstanding Russian scientist, was born in Tobolsk in 1834. In 1850 at the age of 16 h entered the Pedagogical Institute in St. Petersburg to study chemistry. Five years later he graduated from it with a gold medal and was invited to lecture on theoretical and organic chemistry at St. Petersburg University. To continue his studies and research Mendeleev was sent to Germany in 1859. While living abroad he made a number of important investigations.
The year 1868 was the beginning of his highly important Work Fundamentals of Chemistry. When working at the subjects Mendeleev analyzed an enormous amount of literature, made thousands of experiments and calculations. This tremendous work resulted in the Table of Elements consisting of vertical groups and horizontal periods. Mendeleev was the first to suggest the system of classification in which the elements are arranged in the order of increasing atomic weights. The main idea of the Periodic System is the idea of periodic repetition of properties with the increase of the atomic weights.
Arranging all the existing elements in the Table Mendeleev had to overcome great difficulties, as a considerable number of elements were unknown at that time and the atomic weights of 9 elements (out of 63) were wrongly determined. Thanks to his investigations Mendeleev was able to predict not only the existence of a few unknown elements but their properties as well. Later the elements predicted were discovered.
More than 350 works created by Mendeleev deal with a great many subjects. Combining theory with practical activities he carried out enormous research in coal, iron and steel industries in Russia. He died in 1907 at the age of 73.
The achievements in chemistry and physics at the end of the 19th and the beginning of the 20th century made it necessary to reconstruct the Periodic Table taking into account new discoveries.
Time is the severest judge in the science. After more than 100 years of its existence, the Periodic Law has preserved its full value and is being constantly developed with each new discovery.
Robert Einstein
Albert Einstein, a well-known German physicist and mathematician was born in Germany on March 14, 1879. His unusual ability to mathematics and physics began to show itself at a technical school in Zurich. At the age of 21, after four years of university study, Albert Einstein got a job as a clerk in an office. But already in 1905 he made revolutionary discoveries in science. He published three papers in the field of physics and mathematics. In the first he explained the photoelectric effect by means of Plancks quantum theory. The second paper developed a mathematical theory of Brownian motion. He presented his third paper on Special Theory of Relativity to a physical journal. Einstein expressed his theory in the equation E=mc2, roughly that energy equals mass times the square of the speed of light.
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All over the world scientists read the work with great surprise. Few physicists understood its importance at that time. Everybody wanted to know as much as possible about the author. In which institute did he teach? In what laboratory did he do his research?
Einsteins fame among scientists grew slowly but surely. For a few years he lived in Prague where he worked as a professor. When he came to Prague, he often told his students: I shall always try to help you. If you have a problem, come to me with it, we shall solve it together.
He liked questions and answered them at once, for there were no simple or foolish questions for him. He spoke much with his students about scientific problems and his new ideas. His advice to students was: Dont take easy problems.
In 1921 Einstein got the Nobel Prize in physics not for the theory of relativity but for a logical explanation of the photoelectric effect.
After the Great October Socialist Revolution in Russia Einstein became a true friend of the young Socialist Republic. He established scientific contacts with his colleagues in Soviet Russia.
In 1922 he became a foreign member of the Russian Academy of Sciences for his outstanding contributions to physics and mathematics.
On March 14, 1979 by UNESCO decision all people throughout the world celebrated the birth centenary of the great 20th century scientist.
Our Star the Sun
What do you know today of the nearest star which lies 150 million kilometres away?
The Sun is a mass of flaming matter, the temperature at its surface is above 5,500 degrees Centigrade, the temperature at the Suns centre is as high as 20 million degrees Centigrade. The Suns diameter is 109 times that of the Earth and its mass is 330,000 times greater.
The illumination of the Earth by the Sun is 10 billion times stronger than that by Sirius, the brightest star of the northern hemisphere. But this does not mean that the Sun is bigger than Sirius: it is simply nearer the Earth.
Nine planets with their satellites revolve round the sun due to the force of universal gravitation. It takes our Earth a little more than 365 days to revolve round the Sun.
The Sun is the most important body in the Universe for mankind. It provides us with light during the day and the light of the moon is only the reflected sunlight.
It is also important that the Sun gives us heat without which no life can exist on the Earth. It provides us with all the energy that we use every day.
When we look at the Sun, it seems a fire ball. But even from a brief acquaintance with some of the solar phenomena it is clear that the Sun is an ever boiling ocean. The Sun is a giant natural hydrogen bomb, equivalent to millions of man-made ones where the thermonuclear reaction proceeds continuously.
It is interesting to note that every second the Sun sends into space as much energy as mankind consumed during the whole period of its existence from the first fire of the cave-man to the establishment of atomic power station.
Solar energy has great value to mankind.
Man has tried to use solar energy since the earliest times. Methods of using the light and heat energy from the Sun are not new, but they are not very efficient as yet.
It is necessary to find effective methods of utilizing this immense supple of free energy, to make our star the Sun serve mankind.
