|
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: 305 TIME: 0:30:00 DATE: 2007-1-30 In the argument, the author claims that the water in Earth's oceans must have originated from comets. To support this conclusion, the arguer cites the principle that after the collision of space rocks, the water could be evaporated because of the high energy and then be approached by stronger and stronger gravitation of the Earth. It seems that the argument is sound and persuasive, however, after the careful research on it, I find it not convincing as a result of many logical flaws. Firstly, the arguer makes a logical mistake of wrong analogy. As we know, every thing in the world is different from another one, so even if they are in the same situation, there will be various processes because of the different characters they have. So in the argument, the arguer has no evidence to prove that the collision of both space rocks and comets can lead to a same result. For example, while the collision of space rocks can product amount of heat, the collision of comets will only form little energy which can not evaporate much water. Hence, the conclusion that the result of the collision by both space rocks and comets are same is not exactly proved. Besides, the arguer fails to prove that the ice on comets will evaporate after the collision between the Earth and comets. It is possible that the ice made up of frozen water and gases is so solid that it can not be evaporated by the heat from those collisions. In this case, the water vapors which retained in the atmosphere and eventually fell as rain into the oceans are not from comets but from some other planets and in space. What's more, the arguer ignores that there would be some other origins of the water vapor in the space after the collision, besides the evaporated water from the ice made up of frozen water and gases. It is possible that there are some water on other planets nearby is evaporated by the great heat and energy release from the collision of the Earth and comets. So when the planet approached its current size, the vapor water hold by the Earth to form atmosphere is conclude both the water evaporated form the comets ice and the water form some other planets. To sum up, the argument is not persuaded because of some logical mistakes. To make the argument convincing, the arguer should gain more evidence of the familiarity of the collisions by space rocks and by comets and the ice on comets can be gasified by the heat of the collision. Meanwhile, the author should also prove that there are no other origins of water vapor. |