【Flyer杀G】小组-7.16作业 argument50

wagner1985UID: 2838595

50. 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."



难度：★★★★★
Assuming gravitational energy is huge enough that any water in the planet would be vaporized and evolved into the atmosphere, author allegedly believes that the water in Earth's oceans must have originated from ices in the comets which have been vaporized and contained under the atmosphere. However, the argument based a series of unproven ideas.
To begin with, the author assumes that collision of space rock was fierce enough to molten the whole celestial body including the water which had existed in the rock before. However, the author fails to justify the hitting rocks may contains any water before collision, and it may not have any water at all. As we all known that, many planets or satellites hardly contain any water, such as moon and mars. Even if the water really existed before the collision, the collision may incur some conditions of other chemical reaction which can transform the water into other things but not simply go through a physical process, as some radioactive elements would explode when touching the water.
Also, the author assumes that during the planet approaching current size, its gravitation became strong enough to hold gases and water vapor around it as an atmosphere. According to the Law of universal gravitation, the more mass an object has, the more gravitation it will cause. If, as the author claims, everything in the rock either be molten or evaporated, then the rarity is supposed to become smaller rather than bigger. So it is illogical to assume the gravitation will reach its maximization when the rock reaches its current size. And the author really does not give more evidence to exclude other kind forces, as some theoretical physics theory saying, at least there are four kinds of forces in the universe, while the author only highlight the gravitation of the rocks.
And even if gravitation really dragged strong enough to hold gases and water vapor around it as an atmosphere, the water in the ocean still unlikely originates from the comets. At least, the part of water may come from the water which has been vaporized from the rocks. Or else, some water-drop in the universe or other stars could be attracted by the gravitation, which is not seriously considered by the author. Therefore, the final conclusion may amount to a false supposition.
To strengthen the argument, the author should introduce a more complete mechanics model to explicitly describe the whole process from the collision to the formation of atmosphere. And the author has to theoretically exclude other possibility of some chemical reactions, which may happen in the rocks with water, and the coincidence that water in the ocean partly comes from space or rarity in the earth.

candygegeUID: 2792059

Argu 真的有点不知道要怎么改了。你的论述很有条理，也比较有说服力。值得学习。
有一点小的问题，就是在提到行星时，月球应该是the moon，火星是Mars.