We live in the age of great developments in science and engineering. More than two hundred years ago the invention of the textile machinery started the industrial revolution. In less than a century machines were in use in all branches of industry. They were to make all kinds of operations of a factory worker. In fact they could make them much better, much quicker and at a lower cost than factory workers did. Moreover, a machine could do work which a man wasunable to do. Thus the first industrial revolution freed man’s hands from hard and monotonous labour.
At the end of World War II a second industrial revolution began.
The invention of electronic computers makes it possible to free man’s brain from the labour of measurements and computation.
Accurate measurements and exact computation are the bases of modern engineering and scientific research, therefore every engineer must determine accurately the amount of any change that his material has to undergo in different conditions.
Every scientist will make numerous computations before he can say that the results of his experiments are correct. Yet there exist complex computations in science and engineering which the scientists are unable to make because they are too long and too complicated. Here is an example which can illustrate how much time some of them may take. For the accurate forecasting of the weather a meteorologist must make about one million of operations. In order to be able to forecast the weather one day in advance, he has to work with a numerous group of assistants for ten days. This is not the only example; there are many others.
When the first electronic computers went into operation in 1945 their importance for science and engineering became evident. They can work very quickly and make no errors. Any computer is a machine that gives information. A computer cannot create any new information, though it may transform it into a more useful form. By analogy we may call a computer a mathematical translator in the same sense that a translator takes information in some language and translates it into another. We may divide electronic computers into two groups: machines that can measure and those that can count. The latter can add, subtract, multiply and divide. Such machines are to do any operation which we canreduce to arithmetic. Besides they must be able to combine many problems and take them in any order.
Computers are of great help to our specialists, that is why we widely use them in different branches of science and engineering.
Salt is one of the most common minerals used in everyday life. Primitive people that lived mainly upon raw meat did not need salt. Meat itself retained natural salts. When people passed on to the agricultural stage and began to raise crops, salt became a necessity. Bread and vegetables were not only improved in taste, but the salt itself was required for the body’s well-being.
Primitive people believed that good crops depended on the god’s will. So salt was offered to the god’s together with bread and wine.
The fact that salt could preserve food made it the symbol of lasting quality. To offer salt to somebody at one’s table was a sign of friendship.
Some of the great roads in ancient times were built to make the transportation of salt easier.
In Abyssinia and Tibet where salt was greatly needed, it was used as money.
Common salt consists of two elements – sodium, a bright, soft metal, which takes fire in contact with water, and of chlorine, a greenish-yellow gas. It is therefore called sodium chloride.
Salt can be dissolved in water and obtained again unchanged by evaporating the water. It forms the greater part of the dissolved material in sea water and in certain lakes.
Rock-salt is a kind of salt left when sea water evaporates. In places separated from the sea by sandbanks the sea water evaporated and left layers of salt crystals. Then the sea covered these places again, again the water evaporated and left more salt. This process was repeated many times and resulted in beds of pure salt, sometimes 100 feet thick, which were finally covered by mud and sand.
In Abyssinia there is a lake, 7 miles across. Half the bed of this lake is dry and consists of white sea salt.
Salt can be obtained either by mining rock-salt or by evaporating sea water in the salt wells situated near salt deposits. Sometimes the sea salt is frozen out of the solution. But usually the solution is evaporated under reduced pressure. The pure salt crystallizes out first and if necessary can be collected and recrystallized.
When salt is to be used for industrial purposes it is generally taken as mined.
3. THE SOLAR SYSTEM.
There is nothing more important to life than the sun. It gives us heat, light, power and food and all the beauty of colour and form in nature. The sun is a star. There are many thousands of stars in the sky that are like the sun. They are as large as the sun, as hot as the sun and contain the same chemical elements. The sun is a great mass of white hot matter. The temperature at the sun’s centre is as high as 10,000,000 C.
The sun is much nearer to us than other stars. That’s why we think that it is bigger and brighter than other stars. The average distance from the sun to the earth is as much as 150 million kilometres. It is difficult to realize such a distance. But it is much more difficult to realize the distances to the stars which are millions and millions kilometres still farther away. To express these great distances the astronomers use a very much larger scale than kilometres. Nothing in the world moves faster than light. It moves at the rate of 300,000 kilometres per second. So the astronomer’s unit of measure is one light year, the distance that light travels in one year. It is a little less than 9.5 million kilometers. Most of the stars are thousands of light years away from the earth. It is hard to realize that these are not the greatest distances in the world.
Our sun and our earth, our moon and the planets, meteors and comets belong to the “family of the sun” which we call our “solar system”.
Our solar system consists of nine planets and their moons.
The closest planet to the sun is Mercury. No other planet receives more light and heat than this one. It is the smallest of the planets. Mercury revolves around the sun at a higher rate of speed than other planets. Its speed is much higher than theirs.
Jupiter is the largest planet in the solar system. Venus is not so large as Jupiter, but it is the brightest planet in the sky. We see its quiet light in the morning as well as in the evening. When it is in the West it is the first point of light which we see in the evening. We see it best of all on a dark night. The darker the night grows the brighter it shines and the better we see it. When Venus appears in the East it is possible to see it in the early morning hours as well.
Mars shines with reddish light. The appearance of Mars varies from year to year. It depends upon the distance of the planet from the earth. It is closest to us every two years and two months. At such times Mars looks like a red lamp in the sky. Mars has an atmosphere though it is not so dense as that of the earth. Most astronomers think that there is plant life on Mars. Astronomers of all the world observed the last opposition of Mars when it is nearest to earth and took photographs of the planet.
The results of their most important observation will help them to make a better study of the nature of Mars.
Metals are elements. There are about seventy metallic elements. Mendeleyev, the great Russian scientist, was the first chemist who showed the elements arranged according to a definite system. Arranging them according to their atomic weights we find similar elements at certain definite intervals. Mendeleyev’s system is called the Periodic Law. The Periodic Law as stated by Mendeleyev is of great importance for science. It allowed to put into one orderly table almost all known chemical elements and enabled Mendeleyev to make several bold suppositions proved later by experiments. In arranging the table the Russian chemist was obliged to leave several blanks in order to put the elements of similar properties in the same group. These blanks stood for undiscovered elements. Mendeleyev predicted not only the existence of these elements but their physical and chemical properties as well. He predicted the properties of what he called eko-aluminium, which when finally discovered was called gallium. Titanium, discovered 40 years after Mendeleyev’s death, found its place in the great scientist’s periodic table.
The first amount of titanium produced when examined indicated that the metal had promising properties.
There are large deposits of titanium located all over the world. It is the fourth most abundant structural material in nature. Our country possesses rich sources of titanium. In fact,”ilmenite” is the name given to titanium, for the Ilmen mountains in the Urals are very rich in this metal. Titanium has many advantages over other metals. Titanium is light-weight, strong and corrosion-resistant. It has a high melting point. Engineers find wide use for this high-strength metal and prefer it to aluminium which loses its strength rapidly when subjected to high temperatures. Titanium is one of the most useful structural materials applied for making ships, airplanes, cars, bridges, turbines. Engineers believe that it will find many other fields for its application.
Physics is the science studying various phenomena in nature. Its object is to determine exact relations between physical phenomena.
Physics is divided very naturally into two great branches, experimental and theoretical physics. The task of the former is to make observations and carry out experiments. On the basis of the experimental facts theoretical physics is to formulate laws and predict the behaviour of natural phenomena.
Every law is based on experiments, therefore it is important that experiments be done very accurately. It was the study of natural phenomena that made it possible to formulate various laws.
There are still a lot of problems to be solved. Scientists all over the world are doing their best to find an answer to numerous yet unknown phenomena.
6. MEASURING TIME.
If two alternating current generators are coupled together to carry a load, they run at exactly the same speed if they have the same number of magnetic poles.
If one of them makes 90,000 revolutions per hour then the other one will make 90,000 revolutions in the same time, neither more nor less. They work as if they were geared together. If the load were transferred to one machine the other would continue to run and if we no longer drove the second machine, the first would continue to drive it as a motor. Those two machines would continue to run in step so long as they are connected together unless the rotation were resisted by excessive force. We say that the machines are “in synchronism” if they are in step with one another.
Certain motors which are used in industry are designed to run in step (to be in synchronism) with the supply and are called synchronous motors.
On a large electrical system all the synchronous motors must run uniformly at synchronous speed. Even if they ran at different speeds the speeds would be in an exact ratio, and a six-pole machine would turn at precisely two-thirds of the speed of a four-pole one.
It was realized years ago that if the frequency of the supply were controlled carefully, the synchronous motors could be used as clocks. The next obvious thought was naturally that if the frequency were so controlled, the clocks could be fitted with little synchronous motors. Today we consider the electric clock, driven from the supply by means of a tiny synchronous motor quite an ordinary thing.
But suppose we were in a small country town of England some time before 1830. At that time there was a town clock, and most of the townspeople had clocks in their houses and even carried fine watches. These were mechanisms of great accuracy; still they lost and gained time and had to be reset from time to time, but reset to what?
Had the telegraph existed at that time it would have been easy to know the time. If the radio had been invented it would have informed you of the exact hour. Had the telephone been in everyday use you could have inquired and got a ready answer. But there were no radio-sets, no telephone, nor even a telegraph. You could reset your clock by direct observations of the sun or by a sun-dial. However, the time given by a sun-dial does not keep in step with the time given by the clock, as the sun-dial shows the time proper to the place where you live.
When the railways had been invented, an idea was put forth to use the electric telegraph to transmit time for clock-setting purposes.
Today the clock has become the world’s timekeeper. The clock of our days requires little attention. Electric clocks make timekeeping more accurate and require practically no care.
Besides, the telephone tells us the time automatically and the radio informs us about the time every few hours, and it is extremely accurate time too.
With the development of atomic energy it has become possible to measure time by means of an atomic clock. It is extremely accurate. The scientists say: “If an atomic clock had been set at the beginning of our era it would have lost or gained not more than half of a second by now.”