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标题: Can anyone help me with this question? [打印本页]

作者: qiushuan 时间: 2011-7-10 11:11
标题: Can anyone help me with this question?
9. Determining the authenticity of purported pre-Columbian artifacts is never easy. Carbon-14 dating of these artifacts is often impossible due to contamination by radioactive palladium (which occurs naturally in the soils of Central and South America). However, historians and anthropologists have evolved two reliable criteria, which, utilized in combination, have proven effective for dating these artifacts. First, because authentic pre-Columbian artifacts characteristically occur in a coarse, granular matrix that is shifted by major earthquakes, they often exhibit the unique scratch patterns known as gridding. In addition, true pre-Columbian artifacts show a darkening in surface color that is caused by centuries of exposure to the minute amounts of magnesium in the soil of the Americas.
The criteria above would be LEAST useful in judging the authenticity of which of the following?
(A) An ax head of black obsidian, unearthed from a kitchen midden
(B) A pottery bowl with a red ocher design, found in the ruins of a temple
(C) A set of gold ear weights, ornamented with jasper pendants
(D) A black feather cape from a king’s burial vault
(E) A multicolored woven sash found near the gravesite of a slave

the answer is D. I can hardly understand it. Can anyone help me to figure this out? thxs!

作者: sdcar2010 时间: 2011-7-10 11:36
1) Carbon-14 dating of these artifacts is often impossible due to contamination by radioactive palladium (which occurs naturally in the soils of Central and South America).

So if an artifact is digged out of dirt, it would be contaminated.

2) To remove the palladium contamination, we need two extra tests: i) the unique scratch patterns known as gridding due to earthquake; ii) darkening in surface color due to exposure to magnesium.

Let's take a look at D). It is digged out of dirt. So it is contaminated by palladium and we need to use the two extra tests. It is a feather. So there is no way to tell if there are "scratches" caused by an earthquake. Moreover, it is black. So there is no way to tell the "darkening effect" in its surface color. Then D) is useless to be determined by the analytical method.

作者: qiushuan 时间: 2011-7-10 16:16

1) Carbon-14 dating of these artifacts is often impossible due to contamination by radioactive palladium (which occurs naturally in the soils of Central and South America).

So if an artifact is digged out of dirt, it would be contaminated.

2) To remove the palladium contamination, we need two extra tests: i) the unique scratch patterns known as gridding due to earthquake; ii) darkening in surface color due to exposure to magnesium.

Let's take a look at D). It is digged out of dirt. So it is contaminated by palladium and we need to use the two extra tests. It is a feather. So there is no way to tell if there are "scratches" caused by an earthquake. Moreover, it is black. So there is no way to tell the "darkening effect" in its surface color. Then D) is useless to be determined by the analytical method.

-- by 会员 sdcar2010 (2011/7/10 11:36:43)

awesome!!! it makes lot sense to me now!

作者: miffyhui 时间: 2012-4-7 19:02
解释得太好了！！

作者: wendydou 时间: 2012-8-9 14:54
terrific！！！

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