Category Science

Where would you find live prehistoric fish?

Numerous fossil remains have been found of coelacanth fish which died over 70 million years ago. In fact the coelacanth is said to have first appeared some 350 million years ago.

      But to the amazement of experts the first living coelacanth was found in 1938 off the coast of South Africa. In 1952 a second one was caught on a line by a fisherman from the Comoro Islands, between Mozambique and Madagascar. Since then many more coelacanths have been taken around the Comoros.

      Modern coelacanths are bigger than most of the fossil forms. They average about five feet in length and can weigh more than 100 pounds.

      Usually they live among reefs, from which they will dart out on their prey. they are strong and powerful flesh eaters. The heart of a coelacanth is an S-shaped tube and is probably the most primitive of its kind in existence today.

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Why do bats make high-pitched sounds?

Bats use high-pitched sounds to find their way about. They are nocturnal animals. That is they move about by night. So they have developed their hearing to such an extent that they can find their way by a method known as echolocation.

     The blind-flying abilities of bats were first studied by LazzaroSpallanzani (1729-1799). He surgically removed the eyeballs from several bats to prove that they did not need to see to fly.

    In the 20th century, biologists, using electronic instruments, have carried out experiments with bats. They have discovered that bats find out where to go by emitting high-frequency sounds and receiving the echoes as they bounce off objects. Most of the sounds have too high a frequency to be heard by the human ear.

    Bats commonly fly together in groups, but apparently they are not confused by he sounds and echoes produced by each other. When hunting in woods and in the rain they are able to discriminate between the faint echoes bouncing off the ground, tree-trunks, branches, twigs and raindrops.

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When were contact lenses invented?

The first contact lenses were made by A.E. Fick in 1887, but were not successful. During the early part of this century opticians tried to produce extremely thin shell-like lenses to fit closely over the eye. An impression was taken of the eye and a glass shell made which, with a suitable fluid under it, covered most of the eye. After 1938, plastic was used instead of glass, and in about 1950, smaller lenses were introduced which covered only the cornea and floated on a layer of tears. These lenses, only 7 to 11 mm in diameter and 0.1 to 1mm thick can usually be worn all day without being removed.

    Besides being invisible, contact lenses provide a much wider field of vision than spectacles. They are more practical for use in active sports because they are not easily lost or broken, and they can be tinted for use as sunglasses. But contact lenses are not effective in all cases of eye trouble. They are also expensive, and some people find difficulty in learning to wear them.

    As research continues, even smaller and more flexible lenses are being developed.

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When was the thermometer invented?

 

 

The fist practical thermometer or instrument for measuring temperature was invented shortly before the end of the 16th century by the famous Italian astronomer Galileo. It was an air thermometer giving only a rough indication of the degrees of heat and cold, and later he increased its efficiency by using alcohol instead of air.

       The principle on which most thermometer work is that a liquid or gas used for measuring expands or contracts with changes in temperature more rapidly than the glass containing it. Thus when a coloured liquid is confined in a thin glass tube the difference in expansion, as shown by the level of the liquid against a graduated scale, indicates the temperature.

    About 1714 the German scientists Gabriel Daniel Fahrenheit designed a thermometer which, for the first time, used mercury as the measuring agent. He also introduced the scale named after him in which 320 is the freezing point of water and 2120 the boiling point. Mercury is still used in most thermometers because it has a high boiling point (6740) and a low freezing point (-380).

    An alcohol thermometer, still in use in some countries, was made by Rene de Reaumur, a French naturalist, about 1731. About 11 years later Andres Celsius, a Swedish astronomer, used the centigrade scale for the first time, with freezing point 00 and boiling point at 1000.

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Who first used a powered dental drill?

The first powered dentist’s drill was made by George Washington’s dentist, John Greenwood, who adapted his mother’s spinning wheel with its foot treadle to rotate his instrument.

    Earlier dentists had operated their drills by means of bowstrings, a method which must have required skill, determination and physical stamina on the part of the dentist, as well as a great deal of courage from the patient. Later drills were operated by turning a handle at the side.

In 1829 James Nasmyth, the Scottish inventor of the steam hammer, used rotary power to improve the efficiency of the drill. A hand-operated drill with a flexible cable was patented by Charles Merry, an American dentist in 1858; and George Harrington, an Englishman, invented in 1864 a drill driven by a clockwork motor.

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What does an X-Ray show?

X-Rays are electromagnetic rays of very short wavelength which can penetrate matter through which light rays cannot pass. We call this opaque matter. An X-ray photograph shows a picture of the internal structure of the body allowing doctors to diagnose broken bones and examine the organs of the body. In order to show the position and shape of the stomach and intestine harmless liquid containing barium is swallowed, and other opaque substances may be injected to show the outlines of other organ. Oxygen can also be injected into the brain to make its outline sharper.

        The discovery of X-rays was recorded in January 1896 by Professor Rontgen, Professor Physics at Wurzburg. Chest X-rays led to the early diagnosis of pulmonary tuberculosis and from these beginnings the science of radiography and radiotherapy developed until now countless X-rays installations are in daily use throughout the world. X-rays are used both to diagnosis and to treat deep-seated diseases like cancer. Scientific laboratories use them in experiments while industry uses them in work of investigation. By using high-tension apparatus giving up to 300,000 volts, steel can be examines for faults and hidden weakness can be discovered in aero plane construction.

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