The Universe (Part 1)

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Jul 24, 2010 01:44
What is the world? What is existence?
There can be several answers for these questions, a philosophical one, a scientific one, a religious one, and so on.
Science can give only a limited answer for this kind of questions. But I believe that physics will provide at least one possible description of the world someday. Today I'd like to explain about my graduate research - astrophysics.
It has been long believed that gravitation is an attractive force which attracts masses each other. But in the theory of general relativity, which was introduced by Albert Einstein, gravitation is explained as a "curve" of space and time. According to this theory, when there is a mass (or equivalently energy) at some point, space and time around it are curved by the presence of it. For example, the space around the Sun is curved by the mass of the Sun and the Earth goes "straight" along this curve. We observe this as a motion of rotation, and it appears as if it were caused by their attraction.
This theory also showed us the possibility that space and time expand or contract. And later, the expansion of the universe was discovered actually.
This amazing fact also implies that the ancient universe was smaller than it is today. At the very beginning of the universe, everything including us was being packed in one point. Recent researches also have shown the possibility that in the very early universe and the current universe, the expansion was/is accelerating. This might be explained by the effect of "dark energy" which is an unknown constituent which occupies the considerable part of the universe. In fact, more than 95 percent of the components of the universe are unknown ones, "dark energy" and "dark matter".