2. Tensile strength — технический предел прочности на разрыв

THE PROMISING FIELD OF HIGH-PRESSURE RESEARCH

Subjecting materials to high pressure greatly changes their properties. When compressed under more than 500,000 pounds per square inch ordinary liquids become solids. Gases become liquids. Some rocks stretch like rubber. In­sulating materials begin to conduct electricity. Water freezes at room temperature into dense heavy cube's which explode violently when the pressure is suddenly released.

The most interesting discovery in connection with high-pressure research is the artificial conversion of graphite to diamonds.

The interior of the earth itself is a high-pressure labora-i tory. The pressure at the centre of the earth is estimated to be 3,000 kilobars.¹ Graphite subjected to the tremendous¹ heat and pressure generated deep below the earth's surface turns to diamond in the course of thousands or, perhaps, millions of years. Today total output of synthetic diamonds in the world amounts to several tons annually.

Metals become increasingly conductive under high pressures. This has led some scientists to suggest that in­creasingly high pressures might cause some metals to be­come superconductive at room temperature. Superconduc­tivity, the complete absence of electrical resistance, has numerous potential scientific applications, but can now be obtained only at extremely low temperatures close to absolute zero.

Today's presses can easily simulate pressures existing under the earth's surface at a depth of about 250 miles. This is the region where most earthquakes originate. Scien­tists hope their laboratory pressure experiments with rocks and metals will increase their understanding of earthquake causes and, perhaps, help them find methods to predict earthquakes.

High-pressure research together with other observa­tions may lead to answer for some of the most basic science questions, among them the question of the origin of solar system and how life began within it.

Note

1. One kilobar equals about 14,500 pounds per square Inch, USES OF ELECTRICITY

Electricity is the power that has made possible the engineering progress of today. Wherever we look around us, we can find this power serving us in some way.

When we use a switch and have our room instantly flooded with light, we seldom think of what is happening to make it possible. Probably the most important use of electricity in the modern home is producing light.

Do you know that the first ever man-made electric light illuminated the laboratory of the St. Petersburg physicist Vasily Petrov in 1802? He had discovered the electric arc, a form of the gas discharge. But in Petrov's experiments the arc flame lasted for only a short time.

^/r i 1876 Pavel Yabloclikov invented an arc that burned like a candle for a long time and it was called "Yablocli­kov's candle". The source of light invented by Yablochkov won world-wide recognition. But while he and several other inventors were improving the arc light, some engi­neers were working along entirely different lines. They sought to develop an incandescent lamp.¹ It was a young Russian engineer, Alexander Lodygin, who made the first successful incandescent lamp. The famous American in­ventor Thomas Edison improved the lamp having used a carbon filament. But it was again Lodygin who made anoth­er important improvement in the incandescent lamp, having invented a lamp with a tungsten filament, the lamp we use today.

Another electric light we use today is the light of the luminescent lamp—a "cold" daylight lamp.² Artificial daylight lamps are much cheaper than incandescent lamps and last much longer. This is the lighting of the future.

The uses of electricity in the home do not end with lighting. There are more and more electric devices helping us in our home work.

But we should not forget that electricity is the most important source of energy in industry as well. A worker in a modern manufacturing plant uses on the average in the machines which he operates over 10,000 kilowatt-hours of electrical energy a year. This means that he uses enough electrical energy to supply seven or eight modern homes during a year.

Automation which is one of the main factors of techni­cal progress today is impossible without electricity.

Our life can't be imagined without telephone, telegraph and radio communications. But it is also electricity that gives them life. In recent years electricity has made a great contribution to radio communication between the space­ships and also between the astronauts and the earth.

Little could be done in modern research laboratory without the aid of electricity. Nearly all of the measuring devices used in developing nuclear power for the use of mankind are electrically operated.

Notes