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5
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."
victoriazhizhi (云端): https://bbs.gter.net/bbs/viewthre ... 3Ddigest&page=6
这道题首先是一段背景知识,这个我们是不能去驳它的,并且还要利用它来作为我们驳斥的论据。"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 in to 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"
接下来的一句话,我们看到了信号词because,显然接下来有一些推论,我们应该要进行驳斥了。“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 , even tually falling as rain on the cooled and solidified surface of Earth.”这是题目的第一个推论。它的因果关系是这样的:
1)因为彗星大部分是冰团组成,而根据背景知识,碰撞会产生热,所以撞击地球的彗星会被蒸发。
2)因为地球的地心引力足以留住气体形成大气层,所以被蒸发的彗星产生的水蒸气会留在大气层,最后降落到地球表面。
这里面的推论完全基于两个未知的事实就是
1)有彗星撞击过地球
2)在地球有足够引力后,有彗星撞击过地球
这两个事实都是虚假的,因此我们可以驳斥如下:
1)没有证据表明有彗星撞击过地球
2)即使有彗星撞击,也有可能是在地球还没有足够引力的时候撞击的,如果是这样,那么水也会被蒸发到太空中。
接下来,出现了第二个信号词Therefore,这是第二个推论“Therefore , the water in Earth's oceans must have originated from comets”。
这个推论就更加好驳斥了。即使有彗星撞击给地球带来一些水,并不能说明地球海洋的水就是源自彗星,还有其他很多可能,可能水更多的是来自元素之间的化学反应,还有可能是其他的星体撞击给地球带来的水等等。
Arhoo: https://bbs.gter.net/bbs/viewthre ... 3Ddigest&page=1
关于50好像已经达成共识比较棘手。我试着分析一下。一下不是一片argument,而是一点分析。本人不是学物理的。以下拙见来自本来就不怎么扎实的中学物理知识。
1.Earth being formed out of the collision of space rocks is only one of the various versions of hypothesis about the formation of Earth none of which has been substantiated yet. The conclusion deduced from such a hypothesis is open to controvercy.
2.Even if we accept the hypothesis, it is still doubtful that the water present would all have evaporated away. Temporature is not the only determinant of evaporation. Under tremendous pressure, water may still remain in the state of liquid despite high temporature and coexists with other molten substances.
3.There is no evidence indicating that the water in comets can successfully reach the surface of the earth. It is possible that the comets evaporates at very exterior of atmosphere and gravitaion is so weak there that the vapor escape in to the space.
4.Even if it can reach the earth, no convincing statistics are given to prove that water in comets can account for so large amount of water in Earth's oceans. there may be other sources:
5.From outside: When the gravitaion became stronger, more space substances, some of which may contain certain amount of water, would be attracted to earth. In addition, comets are neither the only kind of celestial body that would reach the Earth, nor the only kind that contains water. Meteorites may also contain water.
6.From inside:The argument is based on the assumption that water only come from water. If so, what was the source of the first drop of water in this universe? In fact, water can also be produced out of chemical reactions and nuclear reactions, which are possible on Earth. Thus, water may not only originated from the outspace. In fact, there is large amounts of water in the state of vapor come from inside when a volcano erupts. No evidence indicating such water from inside are also granted by comets.
[ 本帖最后由 kito9695 于 2007-3-4 00:17 编辑 ] |
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