Состав атмосферы: почему воздух на 78% состоит из азота и как водяной пар влияет на климат

Recently I wrote a column about water. It was woefully inadequate since I try to keep the column to under eight hundred words and this topic could fill volumes of newspapers. One of the reasons I wrote about water was that the ancient Greeks believed there were only four elements. These were Earth, Water, Air and Fire. We now know of 118 elements but only the first ninety-two on the chart exist naturally. Back to what the Greeks believed, this column is about air. We tend to take things for granted. Water is one but I think the air we breathe is even more so, since it is what we are most familiar with, making it under-appreciated. We call the air around us the atmosphere. It is all around us all the time. We are always in contact with it. It is around us, on us and inside us. Various things in varying degrees can kill you. No air is a sure thing. Why do humans or anything else need the atmosphere? It is because air (the atmosphere) contains Oxygen which is necessary for all life as we know it. We need it to survive by breathing it in and exhaling CO2 (Carbon Dioxide). The atomic symbol for Oxygen is O (a capital letter O). However, it does not exist in our atmosphere in that form. It exists as a diatomic molecule or two Oxygen atoms joined together which we call O2. The other thing that almost nobody knows about the air is that it is not primarily Oxygen. Our atmosphere is 78% Nitrogen and only 21% Oxygen. You may note that this does not add up to 100%. The other one percent of the air you breathe is made up of Argon, Carbon Dioxide, Neon, Helium, Methane, Hydrogen and Ozone in that decreasing order. These make up less than one percent of our atmosphere down here at ground level. You have heard of the Ozone layer and how important it is in protecting us harmful ultraviolent rays. It is ten miles up but it is only about one eighth of an inch thick or the thickness of a couple of one-cent pieces. (I say that because the US has no pennies like we think. There is no United States coin called a Penny). I never think about the air around us being so high in Nitrogen. When I think about Nitrogen I think about fertilizer and how high the first number is on the analysis. A fifty-pound bag of 5-10-15 is five percent Nitrogen (two and a half pounds) and the rest is Phosphorus, Potash and ground-up limestone. The air (gasses surrounding the earth) goes all the way out to about six-thousand miles from the earth’s surface to the outer layer of the exosphere, where about ninety tons a day is lost to outer space. Not to worry. That is a tiny amount percentage wise. We are not going to run out of air any time soon. All we really are exposed to is the bottom layer, which is Troposphere, that extends from sea level to about ten miles up. If you go on to about sixty miles up you reach what is known as outer space. Only rockets can fly up there. Ninety-nine percent of all the gases in the atmosphere exist in the Troposphere which is the thinnest layer and the densest layer of all the atmospheric layers. One element of the air around us is one I have not mentioned at all. It is not really a gas. It is water but in the form of vapor which is it’s natural state. Like I said before, wet a surface and see what happens. The air around us varies from zero percent to four percent water vapor. At any given time, there are about one quadrillion (fifteen zeros) gallons of water in the atmosphere in various forms. That is really not a lot. It is only about three-eighths of an inch of rain over the whole surface of the earth which is 196 million square miles. Now that you have read all about the air around us, take a deep breath. You just sucked in about a pint of air. That is about three ounces of Oxygen, which is keeping you alive. You know what the rest was from all the dribble above. If you really want a shock, look up how many microbes (living organisms) are air-born and what they are. If you do you may not want to take that deep breath.