All about the atmosphere

Mountain climbers often carry little tanks of pure oxygen and so must the pilots of planes that fly several miles above the earth. At those heights there is so little oxygen in the air that people can quickly become unconscious. At a height of 85 miles above the earth there is no oxygen at all and only a very small amount of nitrogen. The atmosphere at this height is almost entirely made up of hydrogen, a very light gas that human beings cannot breathe.

The atmosphere is divided into two layers. Scientists call the bottom layer the troposphere and the upper one the stratosphere. The upper layer, or stratosphere, begins about six miles above the earth. Science still does not know where the stratosphere ends. However, meteorologists (scientists who study the weather and the atmosphere) know that there is no water vapour in this upper layer. There are no clouds, fog, rain, snow or hail in the stratosphere and the air is always brilliantly clear and terribly cold—more than 60 degrees below zero.

The first man ever to explore the stratosphere was Auguste Piccard, a scientist from Belgium. In 1931, Piccard rose to a height of nearly ten miles, using a huge balloon filled with helium, a very light gas. A year later he reached 54,120 feet, which is more than ten miles. Balloons without men in them are often sent hundreds of miles into the stratosphere. They carry instruments that record conditions at different levels. When the balloons come down, the scientists can read the instruments. In the troposphere or lower layer of the atmosphere, it becomes colder as you rise higher above the ground.

The temperature on the tops of very high mountains is always below freezing. For this reason some mountain peaks are covered with snow and ice the year round. About one hundred miles nearer the sun the temperature of the air reaches a thousand or more degrees above zero.