Üds a can coal ever become a friend of the environment? Coal-fired power stations supply
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The Rhine-Ruhr area became the greatest industrial region of Germany, because it had at its heart the great coalfield of the Ruhr. Mining is now almost entirely northeast and westwards across the Rhine. The region contains the greater part of the German iron, steel and heavy 'engineering industries. The great integrated iron and steel plants mostly cluster on the I Rhine waterway. Specialized steel plants and engineering works are more widespread. With a decline in coalmining and the dismantling after World War" of certain steel plants, some of the older Ruhr towns have diversified their industries considerably: vehicles, electrical goods and clothing are now being produced.
ÜDS C Post-war radar has been developed for an enormous range of uses from police radar speed traps to the ballistic missile early warning systems. At sea it is used on ships of all sizes from the super tankers down to pleasure craft, and in the air it guards military and Civilian aircraft against collisions. It is even used to keep track of the orbital junkyard created by innumerable space launches. Radar found an unexpected use in astronomy and space navigation. Radar signals were bounced off the moon in 1946 and reflections were obtained from Venus and the sun in the late 1950s. Subsequently, radar maps were made of the moon and Venus -- not that such long ranges are essential for radar maps to prove themselves useful. For example, satellite borne radar aimed at the earth has actually led to the discovery of previously unknown remnants of a Mayan canal drainage system in Central America.
Long after the discovery of electricity, man found that he could use the great power of water to produce it. At first, he used natural waterfalls. Later, man began to build Dams to generate hydroelectric power. Dams are immense structures which hold back the water of a river and form a lake behind. The water is let through under control and allowed to fall through pipes to the turbines below. The IIIshing water drives the turbines, and as they revolve, they spin electromagnets; these magnets generate electricity.
Why do transformers hum? This is one of those questions which easy but has surprising hidden depths. The simple explanations that electric currents create magnetic fields, and the alternating current of mains electricity used by transformers creates a magnetic field that changes at 50 cycles a second. This in turn triggers a regular motion of the metal molecules inside the transformer, known as magnetostriction. It's this motion that makes the surrounding air vibrate, creating the hum. But why does the metal respond in this way? The answer fies in a property of the electrons in the metal known as 'spin' - a property, which can only be explained by reference to Einstein's theory of relativity, which is beyond the understanding of most of us.
Geologists are especially interested in the mineral content of rocks. All rocks consist of one or more minerals, many of which are needed as raw materials for industry or have properties which make them valuable or useful. Gold, For example, is valuable. Diamonds are both valuable and useful. Coal is also found in rocks, usually underground and it is vitally important as fuel in modem life. Britain is rich in coal because it was covered in dense forest more than 300 million years ago. Coal is formed from the remains of trees and other plants which have gradually been compressed and hardened in the rock structure of the earth.
Glaciers originate in areas that lie above the limit of permanent snow. Thus in tropical climates Glaciers are only to be found at very great heights, whe""'as in polar regions they flow into the sea. The largest Glaciers are found in regions receiving the heaviest snowfall. The great Glaciers of the Himalayas lie in the path of the monsoon, which deposits on them the full measure of its vast water vapour content. The largest Glacierized areas after Antarctica are in Greenland, North America and in central and south central Asia. It has been estimated that the volume of the world's Glaciers and ice sheets exceeds 11,000,000 cubic miles which, if returned to the oceans, would raise the sea-level by some 200 ft, submerging all existing seaports and much land besides.
We are warm-blooded animals. The temperature inside us is generally higher than the temperature outside us. It follows from this fact that, just as a kettle of hot water cools as it loses heat to the air around it, so the human body is continually losing heat. But, unlike the kettle, it does not cool down, for all the time fresh quantities of heat are being generated inside. The body is both making heat and losing some of it at the same time. The loss of heat is con1folled by a very delicate mechanism. The body resembles a thermostat heater in that whilo it gives off heat It manages to remain at the same temperature.
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