Importance of Atmosphere to Human Life
The atmosphere is an important part of what makes Earth liveable. It blocks some of the Sun's dangerous rays from reaching Earth. It traps heat, making for a comfortable temperature on the earth’s surface. It holds the oxygen which is essential for life.
The Habitable Earth: Even though only a tiny amount of the gases in Earth’s atmosphere are greenhouse gases, they have a huge effect on climate. The major ones are carbon dioxide, water vapor, methane, and nitrous oxide. All of these have molecules with three or more atoms. The atoms are held together loosely and vibrate when they absorb energy from electromagnetic radiation incident upon them. Eventually, the vibrating molecule fall back to their ground state, they release this energy in the form of thermal radiation. This radiation is absorbed by other greenhouse gas molecules, thus preventing the heat energy from escaping into outer space.
This process, which keeps heat near the Earth’s surface, is called the greenhouse effect. Almost all of the other gases viz., O2 and N2 have their two molecules bound together tightly – unable to vibrate.
A Protective Shield: The atmosphere protects us and all living things on the earth from dangerous radiation from the sun. In addition to the light we see, the sun also gives off ultraviolet radiation. Much of it is filtered out by the atmosphere. Ultraviolet radiation can destroy living cells causing harm to our skin and leading to skin cancer. Stratospheric Ozone absorbs the bulk of solar ultraviolet radiation in wavelengths from 290 nm - 320 nm (UV-B radiation). These wavelengths are harmful to life because they can be absorbed by the nucleic acid in cells.
The atmosphere keeps us warm: It holds the surface heat on the earth and prevents it from radiating out into space. In a greenhouse people grow plants under the protection of glass or plastic which lets the light come through for the plants to grow, while protecting the plants from cold. We are able to grow plants even in cold weather because the plants stay warm inside the greenhouse. Without the greenhouse effect of the atmosphere holding in the heat, the Earth would be a very hot by day and very cold by night. (Greenhousing effect is NOT altogether detrimental. This is what makes the Earth Habitable!). The greenhouse effect reduces the extreme temperatures between day and night. Closely related to temperature regulation, the atmosphere also gives us weather.
Weather and Climate: Wind, rain, and snow depend on atmospheric circulation. The atmosphere provides cool breezes on a hot day and rain to make the trees and flowers grow. Plants would not grow and animals would not survive without water. Rain provides the water we need and the atmosphere provides the rain. Movement of the atmosphere (wind) evaporates the water from the oceans and carries it and a lot of heat over the land in the form of clouds. It is the atmospheric circulation that distributes heat over the surface of the earth.
Earth’s Surface Processes: It’s the atmosphere that drives the sedimentary cycle and all surface processes of the earth. In doing so, it also influences the major tectonic cycles. Very complex weather patterns including trade-winds and jet streams are part of the atmospheric circulation that distribute heat around the earth. Weather is a function of our atmosphere.
Protection from Extra-terrestrial Objects: Another really important thing that the atmosphere does is to protect us from objects coming toward the earth from outer space. Every day meteors enter the Earth's atmosphere. When they reach the atmosphere, most of them burn up due to the friction with air. The ones that don't completely burn up reach the surface in a much smaller size. The atmosphere thus protects us from this debris that would damage our infrastructure.
It is because of the heat created by friction that the space shuttle had to be equipped with a heat shield to prevent it from burning up as it re-entered the Earth's atmosphere. That heat caused by friction was dangerous to the astronauts but it is very important to protect us from things coming in from outer space.
Importance for Plants: The atmosphere is also important for plants because it contains a small amount of carbon dioxide. Plants use the carbon dioxide (CO2) along with sunshine to carry out the photosynthesis. In this process the plants convert the sunlight, carbon dioxide, and nutrients from the ground into energy for them to grow and oxygen for us to breathe. Without enough carbon dioxide in the air, plants can't survive.
The atmosphere also helps plants grow in another way. Many plants depend on the air to carry pollen from one plant to another in order to create the seeds that are needed to grow new plants. And many of those plants depend on the air to carry the seeds and scatter them around to spread the plants to new areas. Many plants also depend on insects and birds to carry their pollen and their seeds to make it possible for them to reproduce.
This leads to another thing which the atmosphere does for us.
Inter-continental Flight: The atmosphere makes flight possible. Birds and insects could not fly without the air to support them. Without the air, humans would not be able to fly either. The movements of air over the wings of a bird or an airplane creates an upward lift which makes flight possible. Without the lift provided by the air, an airplane would never get off the ground and neither would a bird or a bee.
Interpersonal Communication: One more thing the atmosphere does is it allows us to talk to each other. If you were talking to your friend and there were no air between the two of you, your friend would not be able to hear a thing you said. Sound waves depend on the air to carry them from one person to another. When you talk, your vocal cords cause vibration in the air. That vibration is what we call sound. The sounds are shaped by your mouth and they travel to the other person's ear. The other person hears what you said. Without the air between you and that other person you could be moving your lips but the other person wouldn't hear anything coming out of your mouth.
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Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)