17.4 Getting into Deep Water

The dark depths of the Gulf of Mexico, once frequented by only the sea creatures, are now alive with human activity. Miniature submarines and robot-like vehicles move around the ocean bottom while divers make their way around incredible underwater structures-taller than New York City skyscrapers but almost totally beneath the surface of the waves. Modern-day explorers are using technology worth of Jules Verne and Jakques Cousteau to find fresh supplies of oil and natural gas.Until recently, drilling in the Gulf was concentrated close to shore in water as deep as 9 km. But now the scientists are looking to hundreds of meters deep and 160 kilometres and more from land. The deep water research began in 1984. Since many American companies have built the world’s deepest production platforms of more than 100 stories high.

17.5 Climate and Man

It’s easy to think of the earth’s climate as unchanging, and for many purposes this would be an adequate assumption. However, the climate does change, slowly but continually. Paleoclimatologists have found convincing evidence of major climatic variations. Recorded history going back some 2,000 years clearly shows changes in climate and their effects on man, animals, plants and the landscape. Great migrations of people and animals accompanied periods of unusual cold and prolonged droughts. The movement of plant communities toward different latitudes and different elevations indicate important alterations in climate. The rise and fall of lake levels, particularly those more or less closed from the sea, show period of wet or dry climate. The extent of sea ice and its effect on shipping to the ports of northern Europe point to the warming or cooling of the earth’s atmosphere.

There is no doubt that climate changes continually, and that it did so long before man and his technology came on the scene.

Until fairly recent times, man’s effect on climate must have been insignificant. The discovery and the Industrial Revolution signalled the start of man’s competition with nature on a major scale. Internal combustion engines using such fossil-fuel-powered furnaces and so forth, began to introduce into the atmosphere huge masses of gases, particles, and grey amounts of heat.

As the population of the earth has been increasing at an alarming rate, the quantity of pollutants put into the air has done likewise. There is growing conviction that the increasing concentrations of carbon dioxide and particles put into the atmosphere by human activities are playing an important role in causing changes in climate. Theoretical analysis have shown that small changes in the cloud cover of the earth can have important effects on the air temperature near the ground. Atmosphere pollution might be affecting climate by causing changes in the cloud cover.

17.6 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.