[a习作temp] Argument 50 求拍！ [复制链接]

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发表于 2009-7-7 23:09:51 |只看该作者 |倒序浏览

TOPIC: ARGUMENT50 - From a draft textbook manuscript submitted to a publisher.

"As Earth was being formed out of the collision of space rocks, the heat from those collisions and from the increasing gravitational energy of the planet made the entire planet molten, even the surface. Any water present would have evaporated and gone off into space. As the planet approached its current size, however, its gravitation became strong enough to hold gases and water vapor around it as an atmosphere. Because comets are largely ice made up of frozen water and gases, a comet striking Earth then would have vaporized. The resulting water vapor would have been retained in the atmosphere, eventually falling as rain on the cooled and solidified surface of Earth. Therefore, the water in Earth's oceans must have originated from comets."
WORDS: 408 TIME: 00:30:00 +10 DATE: 2009-7-7 22:37:24

The arguer concludes that the water in Earth's oceans must have originated from comets. To support the conclusion, the author cites the fact that the water would have gone off into space due to the great energy of the planet and the water would retained in the Earth's atmosphere after the comets striking Earth. The argument, however, has some flaws, which will be discussed below.

To begin with, the author unfairly assumes that all of the water, during the period of the formation of Earth, would have evaporated at all. Surely, there is nothing to be absolute. If all the water could be evaporated, why all of the other substances on the planet can not be melted or evaporated and finally disappear from the earth? Perhaps, some parts of the water is originally in the deep center of the planet and as the surface of Earth is melting, they would not be released any more and keep staying under the surface until today.

At the second place, there is no evidence sufficient to support the assumption that the crash between Earth and the comets can make the water inside the comets remains on Earth. It is true that the water in the comets will come out, but it is also possible for the water to evaporate out the planet due to the huge energy the collision released or to compose some solids with other chemical substances, which is more likely, indeed, since it is known to us that the collision is always together with the considerable energy explosion and all kinds of complex chemical reactions.

Last but not the least, even thought it is true that the collision would release water, the author also fails to rule out the possibility that Earth could produce water itself by the substances inside it. Common sense tells us that the water inside the Earth is a kind of composites that may be composed in many ways of chemical reactions. For example, when some certain solids meet the oxygen in the environment with extremely high temperature, the water comes. In short, the running procedure of Earth is too complicated for us to simply decide the accurate information about water.

In conclusion, without the precise evidence of the formation of the water in the ocean, the arguer's viewpoint can not be well supported. To better assess the argument, i would need more information about the procedure of the Earth's formation.