Our Atmospheric “Ocean”
WHEN you stand by the seashore, you no doubt marvel at the ocean’s power, its restlessness, its vastness and depth. You may have wondered how the sea creatures feel, surrounded as they are by water. Thousands of feet down you can find crabs and other sea animals walking on the ocean floor. The tremendous pressure down there would crush a man, but the bodies of these animals are built to tolerate it.
However, have you ever viewed us humans as actually living, in an “ocean” of air? We do. It is far deeper—more than fifty times the greatest depth in the seas. It is subject to more sudden changes in temperature, and is more restless than the watery oceans. Massive streams of air hundreds of kilometers wide and several kilometers deep move at altitudes of ten to twelve kilometers (about six to seven miles) above the earth’s surface. Known as “jet streams,” they blow at velocities as high as 500 kilometers (about 300 miles) per hour. Then, there are violent storms constantly raging in various layers of this “ocean” of air. We are familiar with the gigantic forces released in hurricanes and tornadoes. Also, about 44,000 awe-inspiring thunderstorms take place every day in this great and restless “sea” around us.
Air Has Substance and Weight
Air, though invisible, has substance. Because of this, our atmosphere exerts considerable pressure at earth’s surface—of course, not as great as does the ocean, because air is not as heavy as water. However, air has weight, as is demonstrated by the fact that a helium-filled balloon rises. Helium being lighter than air, the air pushes it up, just as a bubble is pushed up in a glass of water. The average air pressure at sea level is about fifteen pounds (about seven kilograms) per square inch (6.5 square centimeters). At higher altitudes it becomes less dense, therefore lighter. But our “ocean” of air is so extensive that it weighs more than 5,000,000,000,000,000 (five quadrillion) tons.
This air weight means that, at sea level, there is a load of about a ton across your shoulders. But you do not notice it because pressure is pushing in equally on all sides of your body. To offset this outside compression the body maintains an internal pressure, just as the bodies of sea animals have an internal pressure to equalize the tremendous outside pressure from the water surrounding them. This internal pressure that humans have when “at home” in earth’s atmosphere makes it necessary for them to wear pressurized suits when they are “away from home” in space. Otherwise, in the near vacuum of outer space, lungs and blood vessels would be ruptured.
When you are in a strong wind you are convinced that air has substance. And any doubt as to this is certainly removed if you are in a laboratory and see it change into a liquid at about −310 degrees Fahrenheit (−190 degrees Celsius) and into a solid at about −436° F. (−260° C.).
We can, in effect, “see” air even in its normal gaseous state when heat differences cause it to act as a “lens.” The air concentrated densely at some points and thinly at others deforms the light rays so that we see mirages—reflection and refraction of light from things sometimes miles away. The waves we see above a hot radiator give us a small sample of this phenomenon.
A valuable feature of air is its expansive property. Water, in its normal liquid form, will partially fill a container. But air molecules move much more freely and very fast, generally above the speed of sound. Therefore a very small volume of air expands so that it fills the container to its limits. Only the earth’s gravitation prevents the air from leaving and spreading out into empty space. When the size of the containing space is reduced, air molecules increase their speed and give resistance, creating pressure. This characteristic is highly useful. Liquids cannot be compressed appreciably, but compressors can “pack” a great quantity of air into a small container, so that as it is released it can operate pneumatic presses, drills, air lifts, and so forth.
Essential to Life in Many Ways
However, we are primarily concerned with air because of its importance to life on this planet. Air’s main constituent for life is oxygen, which comprises only 21 percent (by volume) of the atmosphere, that is, of the gases that appear in relatively constant proportions.
Oxygen combines readily with other elements or compounds to produce combustion. Thus, when a piece of wood burns, it is actually being rapidly oxidized. Our bodily warmth is maintained by the body’s metabolism in the oxidizing of nutrients. This process also provides energy for brain power, muscular energy, and so forth. That is one reason why the red blood corpuscles, the blood’s oxygen carriers, are so vital and why the brain cells, which use up about one fourth of the body’s total oxygen intake, need this element in constant supply. So active is oxygen that if it were not diluted with other gases in the atmosphere, fires would start at a mere spark and virtually everything would be in danger of being burned up. Besides, no human would live very long breathing only pure oxygen.
But for our very existence and safety the Creator diluted the atmosphere with nitrogen, which constitutes 78 percent of the ‘relatively constant’ gases making up the atmosphere. So we have just enough oxygen, and it is not too concentrated. In our atmospheric “ocean,” nitrogen and oxygen together make up as much as 99 percent of these relatively constant gases. Nitrogen, though, is more than a mere dilutant. It serves other purposes. During a thunderstorm, lightning allows nitrogen to combine with other elements. Then rain carries the resultant compounds to the earth for fertilizer. It is an essential element for many plants.
But even in the less than one percent of the other atmospheric gases we find gases that are either essential for life or that greatly contribute to our comfort. There are the five almost inert, so-called “noble” gases: argon, neon, helium, krypton and xenon. We are all acquainted with the use of argon and neon in lighting, helium in balloons and in many other applications. Methane, hydrogen and nitrous oxide are other atmospheric gases found in nearly constant concentration.
Water Vapor, Ozone, Dust—Important Constituents
Aside from the gases that vary but little in quantity, there are other gases that are found in the atmosphere in different proportions according to time and place. Two of these are water vapor, from zero up to as much as 7 percent (by volume), and carbon dioxide, between .01 percent and one percent. Plants absorb carbon dioxide and give off oxygen. Without carbon dioxide, plant life would die. Ozone, a form or an “allotrope” of oxygen, is also there in small quantities, constituting only about .01 percent of the atmosphere. It is found mainly between ten and fifty kilometers (six to thirty miles) up, and provides a shield from the deadly ultraviolet rays. Who but an all-wise, all-powerful Creator could have made such an atmosphere for the benefit of all living things on earth, with constituents in the right proportions for the utmost safety, comfort and well-being of all?
Water vapor, as a gas in the atmosphere, is the source of rain, mist, snow, sleet and hail. It forms a large proportion of the clouds. Water vapor is produced by the sun’s evaporation of water from the seas and lakes, and from foliage. Without this cycle of rain and evaporation plant life would soon die off the earth. The Bible speaks of this cycle as designed by God.—Isa. 55:10, 11.
Besides minute percentages of the gases sulfur dioxide and nitrogen dioxide, there are solid particles such as dust, soot from smoke, salt from the oceans, pollen, microbes, and ashes of meteors that burn up as they pass through the atmosphere. Dust, except where it is excessive, cannot be called “pollution,” for dust particles are important in forming the nucleus of raindrops and have to do with the sky’s beautiful blue coloring and the rich red of the sunsets. Except, perhaps, for the discomfort to hay-fever sufferers, plant pollen distributed by air currents serves a beneficial purpose also.
Temperatures in the Atmosphere’s “Ocean”
Most of the things discussed have to do with the layer of air we live in—the troposphere. As is common knowledge, the temperature drops with an increase in altitude. However, after reaching a low of about −67° F. (−55° C.) at the top of the troposphere the temperature rises through the stratosphere (where the jet streams are found) to about 28° F. (−2° C.) and drops again toward the top of the next layer (the mesosphere) to −135° F. (c. −93° C.). The temperature in the next layer, the thermosphere, rises, at the height of about 280 miles (450 kilometers), to an amazing 2,700° F. (nearly 1,500° C.)!
The ionosphere is not one of the regular atmospheric “layers,” but is the region (that includes several “layers”) in which the air molecules are electrically charged by radiation from the sun. Its lower boundary is about thirty-four miles (55 kilometers) above the earth and reaches several thousand miles into very, very thin atmosphere. In the ionosphere the beautiful aurora borealis or “northern lights” (and the aurora australis in the southern hemisphere) occur.
In the ionosphere charged air particles “ionized” by radiation from the sun and from outer space create a radio-wave “ceiling.” This makes possible radio transmission over a distance of thousands of miles. Radio waves travel in straight lines and would reach only a limited area, because the earth curves away from under them and they go straight toward outer space. But the radio ceiling “bounces” them back at an angle to a faraway point on earth. Satellites are now used similarly.
By the use of satellites and more refined instruments, a much better understanding of our “ocean” of air has resulted. Much more is known about its currents, temperatures, and so forth. Weather forecasting is consequently becoming more and more accurate. But there is yet much that man has to learn about the atmosphere, which extends, though in a very attenuated state, several earth radii (one earth radius = 3,960 miles [6,372 kilometers]) into space. Many of its mysteries are as hidden as ever, and new ones spring up as space exploration expands.
[Diagram on page 17]
(For fully formatted text, see publication)
The ionosphoro is a region of electrically charged particles, which begins in the lower mesosphere and extends far beyond the thermosphere
280 MILES +2700° F.
50 MILES −135° F.
30 MILES +28° F.
10 MILES −67°F
[Picture on page 18]
A lightning storm prepares nitrogen compounds essential to plant life