Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.

Категории

География Mountains that explode
просмотров - 140

Temperature Scales

Daniel Gabriel Fahrenheit (1686 – 1736) gave his name to the temperature scale which is still used in some weather reports. Fahrenheit was a scientific- instrument- maker from Holland. Here is a belief that one day a cold winter wind came through the window of his room and froze his tea with milk on the table. This made him think of artificial mixtures of low temperatures. The lowest temperature Fahrenheit could produce in his experiments was with a freezing mixture: the scientists mixed ice and ammonium chloride. He called this temperature 0 0F (0 degree Fahrenheit) on his temperature scale. Ice melted at 32 0F and normal human blood temperature was 96 0F. The improved modern version of the Fahrenheit scale uses 32 0F and 212 0F, as the lowest and highest points on the scale. The scale became popular both in Britain and through out the English-speaking world.

Actually, the Celsius temperature scale is taught in all modern schools today. It was introduced in 1742 by the Swedish astronomer Anders Celsius (1701 – 1744), who chose the melting point of the ice as 0 0C and the boiling point of water a

1000C. The scale in between these points was divided into 100 equal degrees and was called a Centigrade or the Celsius scale. The scale was simpler than Fahrenheit’s, and was soon adopted by scientists throughout the world. In 1948 it became officially known as the Celsius scale, which is now part of the International System of Units.

Another temperature scale was made in 1848 by Scottish physicist William Thomson-Lord Kelvin (1824 – 1907). Kelvin knew that when oxygen and other gases were cooled, their volume became smaller. The lower the t0, the smaller the volume. Experiments proved that at certain t0 the molecules do not move, and their energy becomes zero. That represented the lowest possible temperature, and was called absolute zero on the Kelvin temperature scale. On the Celsius scale absolute zero is -273,15 0C.

Since ancient times volcanoes have struck terror and awe into the heart of man: but scientists tell us they do more good than harm. Many of the islands in the seas and oceans have been thrown up by volcanoes. They have thrown up whole mountain ranges too, some of which are very useful because they increase rainfall. The best thing of all, however, is the way the lava from volcanoes enriches the soil. This explains why farmers crowd the sides of volcanoes, risking death and destruction from new eruptions. They can grow such good crops there that they think the risk well worth while.

Some volcanoes are dangerous. Of all the thousands and thousands of them scattered about the earth, only about 500 are active. Perhaps not more than 50 volcanoes are erupting at this moment like Stromboli in the Mediterranean and Izalco in El Salvador 1. Such volcanoes are watched by scientists. Most of the great volcanic disasters have been caused by surprise outbursts from volcanoes which have not erupted for so long that everyone imagines them to be quite harmless.

In 1952, one of these, Mount Lamington, in New Guinea 2, erupted and caused six thousand deaths. That disaster was bad but there have been much worse ones. Think of Vesuvius which erupted in 79 A.D. burying the towns of Herculaneum and Pompeii 3 under its ashes. Have you heard of Krakotoa 4? Thirty – six thousand lives were lost when Krakotoa erupted, and the smoke and dust from the explosion was so thick that it was blown right around the world.

There is so much power in an exploding mountain that man can not attempt to control it. But at least he is learning how to save himself from the volcano’s fury. Scientists are studying volcanoes ways and learning how to tell in advance when they are going to erupt. Thanks to scientists we are not so helpless as people were in earlier days, when they were too often caught before they could even try to get away.