argument50 [0710G 戴三个表冲刺小组] 第10次作业

pinuoUID: 2328081

Syllabus:
    1.地球是太空石头撞击形成，这种学说可靠吗？有没有其他的关于地球起源的说法，如果不是
      这样，则后面的解释就没有了基础。
    2.即使地球是太空石头撞击形成的。如果water vapor没有跑远，完全有一种解释，地球可以strong的把气和水蒸气吸引在在周围形成atmosphere，就可以将其中的water vapor凝结成water形成ocean。   
    3.即使证明地球上的Water是外来的，为什么必须是comets，而不是其他的Planets。即使是我们现在不知道的星球，也有可能有ice和water。
   4. 另外也没有提供证明， comet   曾经 strike 过地球。
   (没有看楼主的解释，根据自己的理解先写了，后面再详细读解释，再做修改，检查自己的思路问题)

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: 403          TIME: 00:32:26          DATE: 2007-8-6 0:45:10

In the manuscript the author draw the conclusion that the water in Earth's oceans must have originated from comets after the analysis which based on the theory of Earth's formation. The argument is problematic in several respects, thus render the conclusion unconvincing as it stands.

First, the author provides absolutely no evidence to support the assertion that Earth was being formed out of collision of space rocks. If there are other assertions about the formation of Earth, the further analysis of where the water of Earth will be less reasonable.

Second, even the author can substantiate the assertion of the formation of Earth, as description in the manuscript, when the Earth was being formed out of collision of space rocks, the heart from those collisions and the increasing gravitational energy of the planet made the entire planet molten, even the surface, and any water evaporated and gone off into space. How can the Earth hold gases and water vapor around it as an atmosphere when the planet approached current size if all the water vapor gone off and flee far away from the Earth. Since the water vapor can surround the Earth as the form of atmosphere, it is highly possible the water vapor can be cooled in the surface of Earth in the form of water which formed the oceans of Earth.

Third, if it is proved that the water in Earth's oceans is from the other planet, the author cannot easily conclude that it is from comets only because comets are largely ice made up of frozen water and gases. Are there any other planets which also are ice, even we don't know exactly which planet has this character. Can we deny their existence only because they are beyond our current knowledge scope?

Finally, the author provides no clear evidence that a comet once stroke the Earth. If there is no comet strike in Earth's history, the assertion that the water vapor was from the vaporized comet and then falling as rain on the cooled and solidified surface of Earth would be based on empty.

In sum, to convince me that the Earth's oceans originated from comets, the author need provide evidence to support the collision theory of earth formation. And the author also need provide clear evidence that there are no planets other than comet has ice. To better assess the argument, I need the evidence that a comet has once stroke the Earth in Earth's history