Category Science

Why is pollution a problem?

Pollution is a problem because man, in an increasingly populated and industrialized world, is upsetting the environment in which he lives. Many scientists maintain that one of man’s greatest errors has been to equate growth with advancement. Now “growth” industries are being looked on with suspicion in case their side effects damage the environment and disrupt the relationship of different forms of life.

       The growing population makes increasing demands on the world’s fixed supply of air, water and land. This rise in population is accompanied by the desire of more and more people for a better standard of living. Thus still greater demands for electricity, water and good result in an ever increasing amount of waste material to be disposed of.

    The problem has been causing increasing concern to living things and their environment. Many believe that man is not solving these problems quickly enough and that his selfish pursuit of possessions takes him past the point of no return before he fully appreciates the damage. It would then be too late to reverse the process.

    Ecologists say we are so determined to possess a new car or washing machine, or to obtain a greater yield from our crops by the use of fertilizers, that we ignore the fact that life depends on a lot of micro-organisms working efficiently.

     For example, if new chemicals were released into the environment, a combination of them might well poison one or more of the different type of bacteria in soil and water, which are essential to keep nitrogen being circulated from the air into organic material, and being cycled back into the air again. If this should happen on a world-wide scale, the air would become unbreathable.

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When does an atom split?

An atom splits when it is struck by a neutron. The nucleus of the atom then breaks into two roughly equal parts and, at the same time, shoots out several high-speed neutrons.

      Atoms are so small that they cannot be seen under the most powerful microscope. They are the building bricks of which each element is composed. The Greek word “atom” means “cannot be cut”. But we know how that atoms can be cut, or split. Each one contains minute particle carrying two sorts of electricity: first the electrons which are negatively charged; and secondly, the central core or nucleus which is made up of protons (positively charged) and neutrons (no charge).

    In the 19th century it was discovered that all elements with atomic weights greater than 83 are radioactive and that the nucleus could be divided into several parts. Albert Einstein (1879-1955) calculated in 1905 that splitting an atom would destroy mass and release heat. By thus converting matter into heat energy, vast amounts of heat would be obtained by destroying only a very small amount of matter.

     Between 1934 and 1938 the Italian Enrico Fermi and the German Otto Hahn discovered that atoms of uranium (atomic weight 92) split when struck by a neutron. In 1939 Fredric Joliot-curie found that this splitting, or fission, released two or three more neutrons which in turn produced fission in more uranium nuclei, and so on. It is this chain reaction that makes possible not only the benefits of nuclear power but also the horrors of nuclear warfare.

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How far can you see?

If you stood on the shore looking across the sea to the horizon (the line appearing to separate earth from sky), you might be able to see about two and a half miles. But he higher you stood the farther you would be able to see. As the earth is curved, the horizon would appear farther away with every increase in the height above sea level.

       At a height of 20 feet you might see for six miles. From the top of a 300-foot cliff your view could extend for 23 miles, while on the summit of a 3,500-foot mountain, it could lengthen to 80 miles. From an aircraft flying at 16,000 feet you might have an uninterrupted panorama for 165 miles.

If you look straight up into the sky, the distance you can see is immense. The moon is about 239,000 miles away and the stars are millions of miles distant.

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What is Radar?

Radar, or radiolocation, as it was called in the early days, is the use of radio waves to find the where-about of aircraft or ships.

    Electromagnetic waves, which include radio and light waves, all travel at the same speed. When small bursts of radio waves, fired into space from a transmitter, strike an object such as an aircraft some of them bounce back and are collected by an aerial. Special equipment calculates the distance of the object from the time taken for the waves to go there and back.

    Direction is obtained by rotating the aerial, and the course being taken by the object is shown as spots of light on the face of a cathode ray tube. So direction, position and movement can be judged accurately.

    Radar was first used to detect enemy aircraft in wartime, and to guide fighter aircraft and bomber pilots. Since then it has proved invaluable in civil aviation by helping the pilot to guide his aircraft in the air and to land it safely in fog or at night.

   At sea it can give the position of land and other ships. Some buoys are fitted with radar, so that they can be located in the dark or in fog. Radar is used also to give warning of turbulent weather.

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Where is Ursa Minor?

 

 

 

Ursa Minor is the name of a group of stars in the Northern Hemisphere. The word used in astronomy for a group of stars is “constellation”.

      The stars and constellations have Latin names. Ursa Minor means The Little Bear. Its brightest star is called Polaris, and is centered over the North Pole. It is of great importance in helping sailors to find their bearing when navigating at night.

    Star maps of the sky will help you locate the constellations.

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What is a star?

A star is a body of luminous gas, like the sun. But as stars are much farther away from the earth than the sun, they appear to be only small points of twinkling light. With the naked eye it is possible to see about 2,000 stars at any one time or place but with the most powerful telescope over 1,000 million stars are visible. Although light travels at 186,000 miles a second, the light from the stars takes many years to reach the earth.

     Stars are not fixed in space, but are travelling in different directions at different speeds.  Seen from the earth, these movements appear to be so small that groups of stars, or constellations, seem to have a permanent relationship. The star patterns we see in the sky are almost the same as those seen by our ancestors hundreds, or even thousands of years ago.

    The sizes of stars vary tremendously, from less than the diameter of the sun to thousands of times its size. Most stars appear white when looked at with the naked eye, but some are bluish-white, yellow, orange and red. The varied colours are due to differences in surface temperature. The brilliant, white stars are the hottest with surface temperatures of several hundred thousand degrees. The less brilliant, orange and res stars have surface temperatures of about 2,000 degrees.

      There are exceptions, however. Te red giant, betelgeux, in the constellation (or group) of Orion, appears to be brilliant because of its size. Its diameter is 250 million miles, which is greater than the diameter of the earth’s orbit round the sun.

     Shooting stars which are sometimes seen moving across the night sky for a few seconds are really meteors. These small particles flare up as they strike the earth’s atmosphere and usually burn out.

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