Argument50 第一次发帖噢～～

倒着走的小妖UID: 2377654

In this draft textbook manuscript, thewriter claims that the water in Earth's oceans must have originated fromcomets. To justify the claim, the writer cites some facts about comets and sometheory concerning the origination of Earth that Earth was formed out of thecollision of space rocks. Despite the credibility of the cited backgroundtheory, the reasoning, nevertheless, rests on several unsubstantiatedassumptions which render it unpersuasive as it stands.

To begin with, the writer unfairly assumesthat some comets have stricken Earth, while he provides no evidence to supportit. It is entirely possible that no comets have struck Earth. Or even if somecomet did strike Earth, perhaps the collision happened before Earth'sgravitation became strong enough to hold gases and water vapor around it.Therefore, the comet vaporized would have gone off to the space as described andthus not have been retained in the atmosphere, let alone having forming theoceans. Without ruling out this and other possible scenarios, the writer cannotdraw any firm conclusion that collisions between Earth and comets providedwater vapor to the atmosphere.

Second, the writer assumes further that noother planets and space objects may have bring water to Earth by collision. Yetit is untenable. Common sense informs me that a myriad of other space objectsincluding meteorites have collided to Earth. What is more, the writer fails toindicate that how many comets have struck Earth and what is the size of those comets.Absent such information, I cannot appreciate whether merely comet-striking haveprovided enough water vapor and hence enough rain to generate Earth's oceans.Lacking clear evidence that the only water-containing out space force strikingEarth is comet, I remain unconvinced about the crucial impact of comet duringthe formation of oceans.

Third, the writer also draw his sweepingconclusion on the additional assumption that water in Earth's oceans all comefrom water vapor in the atmosphere which is the result of collision betweenEarth and other water-containing objects. Nevertheless, as I know, inner spaceactivities such as huge volcanic eruption may also bring plenty of water vaporthat eventually falling as rain to form the oceans. And, basic chemistryinforms me that water is not necessarily come from various states of water. Infact, most water is byproduct of chemical reactions. Therefore, a complete analysisof different source of water in Earth’s oceans is necessary for the writer toconfidently argue that only collision was responsible for the oceans.

In conclusion, the claim that the water inEarth's oceans must have originated from comets suffers from several logicalfallacies. To bolster it, the writer must provide clear evidence that therewere comets striking Earth after Earth approached its current size. To betterassess it, I would need to know that no other out space objects had collisionwith Earth and the water in Earth's oceans were not from the inner activitiessuch as volcanic eruption and chemical reactions.

[ 本帖最后由 倒着走的小妖 于 2007-8-9 19:52 编辑 ]