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Cosmology_Introduction(1)  

2010-08-20 14:46:27|  分类: physics |  标签: |举报 |字号 订阅

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Chapter0: Introduction
    Before giving a formal introduction of cosmology, I would like to say something according to my experience.  
    First, we should ask, what is cosmology, and what we are doing with cosmology?  Cosmology is just a science about our universe, it deals with the origin of the universe, the evolution of the universe.  Recently I begin to have a strong feeling that, doing cosmology is just like studying history!!!  These two subjects do have a lot in common if you take some time to think of it.  In studying history, we know clearly what we are researching, the history is just a set of things that already happened.  But in cosmology, we still have a lot of unknown things,i.e DARK MATTER and DARK ENERGY.  So we really should ask the following question: what is the universe made of?  Actually we still cannot answer this question, the main reason is that we only have very limited observational data about our universe, and it is impossible to make experiments or observations which have very long time scale to help us understand the evolution of our universe, since the whole history of cosmology has a time scale of 15billion years, and the human's history is just a flash compare to it.

    So, what we can do? The only thing we can do is surveying the galaxies and so on, and then doing statistical works to find out those predicted results of theories.  The most famous example is that about the CMB(cosmic microwave background radiation).  Anyway, there are still a lot more to say about experimental observations, I am not an experimentalist, so
if you wish to know more, you can go to wiki to find the answers.

(continued...  20/Aug/2010  Youhua Xu)
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