The Usefulness of The Sun To Planet Earth And Her Atmosphere
The Sun And The Atmosphere
The sun beams upon the earth all the time; without the sun, the earth would, of course, be a barren, lifeless wasteland in space. The sun radiates energy which is the energy that keeps all the plants and animals alive.
But lucky for us, not all the energy from the sun gets through the atmosphere to the surface of the earth. We get just enough energy because too much radiation would be deadly. The atmosphere screens out the excess rays we do not need.
Most solar radiation moves freely through the gases in the atmosphere. Clouds and dust particles set up a barrier. Clouds reflect some radiation back into space. Dust particles absorb many of the rays.
The upper part of the atmosphere absorbs ultraviolet radiation. Ultraviolet rays can be very dangerous because they are rays that give you sunburns. Ultraviolet radiation would cook everything on earth without the upper atmosphere.
Although too much ultraviolet radiation could be harmful; however, it will be the end of life if the heat from the sun no longer reaches the earth. All living things must have light and heat from the sun; Plants and animals soon would die without solar radiation.
The sun, of course, warms the earth. The earth, in return, gives up some of the heat it receives from the sun. It reflects some the heat back into the atmosphere. Reflected heat waves are constantly rising from the earth’s rocks, soil, water, and other surface features.
The reflected heat wave warms the air. The air close to the earth is warmer than most parts of the upper atmosphere. The air is warmer because it touches the earth’s surface. It absorbs a good share of the reflected heat.
As you go higher into the atmosphere, you can soon feel the difference I air temperature. A drop of about 17◦F occurs for every mile of altitude. If the temperature is 80◦F at ground level, the temperature one mile above the surface is about 63◦F.
The temperature continues to fall until it reaches 68 below zero. In the north middle latitude, this reading usually occurs at an altitude of six or seven miles. The constant temperature of -68◦F occurs over the equator at about 10miles up. At the poles, this temperature set in at only five miles up.
The Green House Effect
Rocks and other surface features readily give up their heat. Infact the earth would reflect too much of heat if it were not for some built-in safeguard within the atmosphere. These safeguards are the water vapour and carbon dioxide in the air.
Solar radiation moves freely through the gases in the atmosphere on its way from the sun to the earth. Some of it is then reflected as heat waves. Water vapour and carbon dioxide block the earth’s reflected heat waves. Thus, the earth retains part of the heat from the sun. The reflected heat waves are different from the original solar radiation. That is why they are trapped by water vapour and carbon dioxide.
Solar radiation moves in short waves. Reflected wave’s moves in long waves. These waves are too long to pass through water vapour and carbon dioxide..
The process of trapping waves is known as the greenhouse effect. Rays from the sun easily pass through the glass roof of a greenhouse. The plant in the greenhouse reflects some of their heat. The long, reflected rays cannot get through the glass roof. Thus, the heat is trapped inside the greenhouse.
In a similar way, heat is trapped within the earth. The atmosphere is like the glass roof of a green house. Solar radiations get through the atmosphere. But not all the heat can be reflected back into space.