Timothy Fix, age 1 , of Pacifica, Calf., for s question:
Why is it colder in the mountains?
The earth is warmed b sunlight, the radiant energy which pours forth in all directions from the sun. Since the sun is the source of our heat, it is natural o suppose that sunlight is hotter the near©r we get to the sun. Moun ains are higher and therefore closer to the sun, somewhat, than the rairies. But as everybody knows, mountain breezes are cool and some mountain tops in the tropics are cold enough to wear snow all year round.
The nearer we sit to fire, the warmer we get. But the nature of sunlight and the nature f our atmosphere conspire together to make nonsense of this firesid logic. Sunlight is not heat, but a source of heat energy. It is not transformed into heat as it whizzes across the vacuum of empty space. his cannot happen until the radiant energy of sunlight strikes a solid object. Air is made of gaseous particles and the atmosphere has far more density than the void of empty space. But it is far less dense than the solid and watery surface of the earth. About one part in two billion parts of the suns outpouring energy reaches our planet, It reaches the air first an comes streaming down to the earth.
The atmosphere reflects back into space about 42 per cent of the radiant energy which reaches our planet. It can transform only about 15 per cent of the remaining sunlight into heat. This means that the air gets little or no heat from the sunlight as it streams down to the earth. If this were all the heat it ever got, the air would always be cold, both in the mountains and on the prairies.
The earth can transform part of the sunlight into heat, and does so. Air is heated by the war land and sea below it.
The layer of air sitting on the scorching prairie gets more heat than the layer of air above it. But the atmosphere is restless. Winds and breezes shift and mingle this warmed air with the air around it, We get land and sea breezes as warm and cool currents interchange. Another factor tends to keep the warmest air more or less at sea level. The densest layer of air is at the bottom of the atmosphere. The higher we go, the thinner the air becomes. The air is so thin at the top of, say, Mount Everest that climbers need extra supplies of oxygen. The atmosphere finally peters out hundreds of miles above the ground. But about 80 per cent of the bulk of the air is contained in a layer five to ten miles above the surface.
Normally; the temperature drops as we rise above the surface of the earth. This falling temperature continues until we reach the troposphere, a shell about ten miles above the equator and five miles above the poles. Here the temperature evens off at about minus 67 Fahrenheit degrees.