Secrets of Air

        Air is one of the most mundane substances around us. It is colorless, odorless and amorphous, yet everywhere – we cannot escape from it. On the small scale, air consists of multiple types of molecules, some of which are crucial for the organisms on earth; while on the large scale, air forms the atmosphere of earth, which essentially is the reason why lives can exist on earth. Today, let’s look at air from different prospective and on the way unfold some secrets of air that you may not know.

1. 21, 78, 3, 3, 94

        If you have taken some high school chemistry, this array of numbers may look familiar to you – at least for me, I used this recipe to cram for my chemistry exams. This array stands for the proportions of each kind of gases that consists air. A common mistake that the general public may make is that, air is made of “air molecules”. In fact, the commonly used term, air, refers to a collection of gases including oxygen (denoted by O2), nitrogen (N2), carbon dioxide (CO2), argon (Ar), and some other kind of gases. By volume, air contains approximately 21% oxygen, 78% nitrogen, 0.03% carbon dioxide, 0.03% other gases, and 0.94% noble gases, of which primarily is argon.

2. The weight you cannot bear

        Air seems to be weightless. The situation does not usually happen where you have to make tremendous efforts to just stand up because the air on your shoulders is too heavy. However, air does have weight, and it IS heavy. Let’s verify this argument through some simple math. The air pressure, defined by the force exerted on a unit area, is about 105 Newton per square meter. The area of your shoulders is about 15 cm * 40 cm = 6 *10-3 m­­2. This gives the force on your shoulder by air, F = 6 *10-3 * 105 = 600 Newton = 135 pounds! Well, apparently you do not feel this weight every time you stand up (in addition to your own weight, of course), so how come? The magic spell is that, air is everywhere! This is saying that, while there is 135 pounds of force on your shoulder, there is also the same amount of force from below that “lifts” you, as long as there is air that you “stand on”. Therefore, you should now understand why the suction cup can “stick” your GPS receiver on your wind shield – there is practically no air in the suction cup, so the atmospheric air pressure keeps it there.

3. Refund!!! There is “water” in my bottle of compressed air!

         Some of you may have used compressed air to blow off the dust on your laptop. When you shake the bottle, you will typically hear the sound of “water” pounding on the interior of the bottle. Why there is “water” in the bottle? In fact, the “water” is actually air! Air does not necessarily have to be in the gaseous state, and it can change from a gas to a liquid or even to a solid when you, for example, compress it to a very high pressure. In this case, the pressure forces the molecules to stay closer to each other, and air appears to be a liquid. (Actually, this is the ultimate difference between a liquid and a gas – the molecule spacing.) In practice, this is how people usually store gases – in a steel, high-pressure bearing tank – so that it would be volume efficient.

4. Wind – a troublemaker but also a blessing

        When there is a pressure difference of air between two regions, maybe caused by the different temperatures, air will flow from the high pressure region to the low pressure region. This process creates one of the most common natural phenomena – wind. In a hot summer day, a breeze is almost bliss. However, you do not want the wind to blow too hard; too fast the wind might be detrimental. Tornado is a wind of this kind. Wind is also one of the reasons that accounts for a phenomenon called ocean current. Ocean current is a continuous, directed movement of seawater. The constant winds in the high seas (far away from shore) direct the surface sea water to move along with the winds due to friction, so ocean current forms. Ocean current is a very important phenomenon – it is a dominant factor in determining the climate of many regions! The most striking example is the Gulf Stream, an ocean current originates at the tip of Florida and extends towards Europe. The consequence is that, due to the Gulf Stream, northwest Europe is actually much more temperate than any other region at the same latitude. The famous Peruvian anchoveta fishery is also a result of ocean current, where ocean current brings abundant nutrition to the area.

5. Epilogue

        Although air is so unnoticeable, it affects our lives in nearly every aspect, either directly or indirectly, just as its universal presence. It protects all the organisms on earth surface from serious cosmic radiation, and retains heat on earth so that the temperature on earth surface would not vary dramatically. I would like to end our investigation of air with a question: air is an important industrial raw material. What is air making?

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I spy with my little eye….

How many people can remember their mom telling them not to read in the dark?  Probably many.With all this new technology, there are many new problems to consider. Nintendo recently gave the warning that children under the age of six shouldn’t use the new 3D feature of their 3DS and computer vision syndrome is becoming much more popular.

The warning from Nintendo has raised a lot of questions about the effects of 3D technology on eyes and in particular developing eyes.  The concern Nintendo has is that before age six, it is believed that eyes are in a critical period of development.  Experiments have shown that if a young child cannot see out of one eye after a few years they will not be able to see out of the eye even if the problem is fixed. On the other hand if the same thing happened in an adult, when the problem causing the blindness in one eye is fixed they will be able to see normally again. This is because of how the brain processes the visual information.  The two eyes see slightly different images and then process the information into essentially a column of cells.  When both eyes work, the columns should alternate which eye the information came from by cell. But when only one eye works or is heavily favored then the columns only have information from that eye.  When vision is returned to the eye, the brain doesn’t know how to make the columns start alternating if they haven’t done it before.  It is more than just blindness that can cause one eye to become dominant over another though.  If the two eyes are misaligned or if they focus at different distances, then one eye will generally become dominant to prevent double vision.

In order to begin research on the effects of watching 3D on young eyes, Dr. Tychsen did research on baby Rhesus monkeys. While not a guaranteed indication that the effects observed will carry over to humans, it is very likely that the effects will be similar.  In Dr. Tychsen’s research, he had monkey’s watch 3D films throughout each day for three months.  The monkeys who watched the films had no difference in their visual development compared to those who did not watch the films. In fact, some researchers believe that the only potential concerns for have more to do with how much information the brain has to process and the fatigue that comes from that.

Surprisingly, it turns out that the 3DS may actually have visual benefits in the sense that it could have doctors diagnose issues that may result in learning difficulties in children at an earlier age.  Many vision problems can be treated much easier if they are detected early. The 3DS is essentially showing each eye a slightly different image, so when they combine you get the 3D effect.  Therefore, if one eye is dominant over another, there will be issues when viewing the 3D content as the information will not combine correctly and will not give the correct 3D effect.  When using the 3DS there are 3 signs that you need to get a comprehensive eye exam by an ophthalmologist because there may be an issue.  They are dizziness, discomfort, or lack of depth.

So what about computer vision syndrome?  We’ve all had those days where we’ve stared at the computer for way too long and before we know it, we’re rubbing our eyes, can’t focus and that nagging headache is building up, but why does it happen? Part of it is because of how the computer screen works.  When you stare at an unchanging object, the computer screen is not actually unchanging.  The screen is actually constantly refreshing itself and forcing you to refocus your eyes every time it refreshes.  Another cause is an underlying vision problem that is aggravated by the computer. And as you age, your eyes are changing anyways. So watch out baby boomers…computer vision syndrome is coming with carpal tunnel syndrome for those of you who are on the computer all day.

Proper work place set up.

So what can you do to prevent it? Well you have some options.  The easiest thing is to blink and take breaks more often.  If you blink more frequently as you work, it will help prevent dry eye and breaks will give your eyes time to refocus.  Also make sure you work station is set up properly. The diagram to the right shows the recommendations of the American Optometric Association.  You want the screen below your eyes and just over two feet away from your eyes.  Finally, do your best to reduce the glare on the screen either by changes in lighting or by adding an anti-glare screen.

For more information on these topics, here are some good articles:

  1. http://www.hhmi.org/senses/b410.html
  2. http://www.aoa.org/x17309.xml
  3. http://bits.blogs.nytimes.com/2011/01/05/eye-specialists-question-nintendos-warning-on-3-d-technology-and-children/
  4. http://www.aoa.org/x5253.xml