♥ Monday, January 19, 2009 ♥
Today Mr. Heah taught us the basic knowledge about the composition and structure of the atmosphere. At first, I wondered why we should learn such a common knowledge that everyone knows it in primary school. But later I noticed that it is not as simple as I think.
It is definitely true to say that the atmosphere is essential for life, but why it is? You may say that because it has oxygen and people need oxygen to stay alive, but why oxygen is, why could not be nitrogen since it constitutes 78 percent of the atmosphere? All of these I have never questioned myself before. That’s why when I started thinking them I found that Geography is more than memorizing. It can be linked to other scientific subjects and remembered by thinking logically.
The composition of air basically includes three parts: 78% of Nitrogen, 21% of Oxygen and 1% of other gases. The oxygen plays an important role to sustain our life because of its reactive property. It can form compounds with lots of elements and moderately soluble in water so that we can easily use it as respiration and other necessary biological activities. Other gases like nitrogen and helium, is either too stable or too reactive.
However, there is another gas in atmosphere that only constitutes 0.036%. It is carbon dioxide, the so-called waste product of all living creatures. Mr. Heah asked us what if there is less carbon dioxide in the air. As my opinion, I do not think it is good for us although it may help solve global warming or whatever. Carbon dioxide is as important as oxygen in the world. It is the key of the carbon cycle which helps balance the spheres and interacts properly between the layers. If there is less carbon dioxide in atmosphere, it will also be less carbon dioxide dissolves in the waters of the hydrosphere. Thus, the land plants and aquatic plants can hardly survive without enough carbon dioxide to photosynthesis and make food.
Otherwise, we also learnt the structure of the atmosphere. It has five spheres: troposphere, stratosphere, mesosphere, thermosphere and exosphere. There was one question that puzzled me a lot and I hope someone can provide an answer. Actually Mr. Heah mentioned that it is something about the difference between temperature and heat.
The question is “why the temperature at the thermosphere is higher than 1200 degrees Celsius, yet you would freeze to death up there?”
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Wow, first person to "kena arrow"!
Anyway, I don't believe that the exosphere is so much part of the atmosphere as it is part of space. No protection I can think of up there, either.
Also, in response to the question, I believe that the 1200 degrees only applies to a few atoms (near vacuum up there). Thus, there is not enough contact with the atoms to transfer enough energy to heat you up. Freezing would be the least of your problems anyway...
Calvin
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Incidentally, I found out that "strato-" means "layer" and comes from "stratum". http://jesse.usra.edu/articles/sarma/sarma.html
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Li Qin
From what i understand from the information given on the net, the air in the atmosphere is very thin with individual gas molecules being far apart and thus heat transfer will take a longer time or just like what Calvin said, the molecules may not be able to have any contact to result in transfer of kinetic energy. Also, our bodies will lose heat through radiative emission as compared to the kinetic energy it would gain by making rare contacts with extremely hot gas molecules.This could be the reason why we may freeze to death.
After attending this lesson, I've come to realised how fascinating the atmosphere is and the many components of the atmosphere that help to make lives possible on Earth.
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Viona
Temperature is a number that is related to the average kinetic energy of the molecules of a substance. It is not an energy.
Heat is the total amount of energy possessed by molecules in a substance. It consist of both kinetic and potential energy. Heat is energy.
That is the difference in heat and temperature. I hope this helps.
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I agree with Deng Xuan that studying geography is not just memorizing but also remembering in a systematic way. In my opinion, in each topic, there is some key terms (like the root of a tree) in which if you understand them, you will learn others with ease.
Then, I also agree with Mr.Heah that questions are more important than answers (of course if you crap you answers, you will get zero). Now I understand sometimes when I answer the questions, there are actually extra information in my answers that only waste my time in exams. I think I should read the questions more carefully since now.
About the composition, actually there is no surprised to me as Mr. Heah said "you already know".
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FROM ZILI:
I am still confused with what Calvin said about EXOSPHERE. According to my research on the website (http://dictionary.reference.com/browse/exosphere), it said that EXOSPHRE is the highest region of the ATMOSPHERE, where the air density is so low that a fast-moving air molecule is more than 50 percent likely to escape from the atmosphere instead of hitting other molecules. EXOSPHERE is really a part of ATMOSPHERE, right? And also from my reading, the thin layer of atoms within the EXOSPHERE still have the abilities to absorb and block some of the ultraviolet and x-rays. It does protect us and our earth(:
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I know, the exosphere is part of the atmosphere. It's just a very vague part, so I meant it should be considered as half-space as well. And I don't really think the few rays make much different. Maybe only a few days off your life. But it's protection anyway.
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Wow, first person to "kena arrow"!
Anyway, I don't believe that the exosphere is so much part of the atmosphere as it is part of space. No protection I can think of up there, either.
Also, in response to the question, I believe that the 1200 degrees only applies to a few atoms (near vacuum up there). Thus, there is not enough contact with the atoms to transfer enough energy to heat you up. Freezing would be the least of your problems anyway...
Calvin