在New York Times上看见这篇English报导没有明白氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾,请你浏览下,A Blow to the Oxygen Theory of Extinction By KENNETH CHANGPublished:August 29,2008Call it the clue of the m

在New York Times上看见这篇English报导没有明白氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾,请你浏览下,A Blow to the Oxygen Theory of Extinction By KENNETH CHANGPublished:August 29,2008Call it the clue of the m
在New York Times上看见这篇English报导没有明白
氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾,请你浏览下,
A Blow to the Oxygen Theory of Extinction
By KENNETH CHANG
Published:August 29,2008
Call it the clue of the moss that would not burn.It may show that a suspect in the largest mass extinction in Earth’s history is innocent after all.
For years,scientists have proposed various hypotheses for why about 90 percent of species living 250 million years ago suddenly died out.Some believe it was a meteor like the one that killed off the dinosaurs 135 million years later.Others have suggested massive volcanic eruptions or dropping ocean levels.
One idea that has attracted attention of late is that oxygen thinned precipitously,and animals died out simply because they did not have enough to breathe.But rocks of this era still contain charcoal,which means there was enough oxygen in the air for plants to burn.
So Claire Belcher,a biochemist at University College Dublin in Ireland,went into a room-size atmospheric chamber wearing an oxygen suit and spent a few months trying to burn things in low-oxygen air.Paper would not ignite at less than 14 percent oxygen,and even then,“It didn’t burn with a sustained flame,” Dr.Belcher said.
A candle would not ignite until oxygen reached a level of 17 percent by volume,and highly flammable pine wood did not burst into flames until oxygen reached 18 percent.Moss would not burn at all at less than 15 percent oxygen and did not really catch fire unless oxygen reached concentrations of 17 percent.Oxygen makes up 21 percent of present-day air.The results appear in the Aug.29 issue of the journal Science.
Dr.Belcher said the results did not rule out the oxygen hypothesis — the charcoal data is not detailed enough to detect an oxygen drop lasting just 100,000 years or so.But,she said,proponents of the idea need to look for more evidence in the rocks.

在New York Times上看见这篇English报导没有明白氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾,请你浏览下,A Blow to the Oxygen Theory of Extinction By KENNETH CHANGPublished:August 29,2008Call it the clue of the m
长久以来.科学家们一直对于物种的大灭绝有各种各样的假设与猜想.最近有一个假设吸引了人们的注意力.它认为动物灭绝是因为空气中的氧气浓度下降,动物们没有足够的氧气才最终灭绝.爱尔兰都柏林大学的生化学家Claire Belcher穿着带有氧气的服装,在一个房间大小的容器中,对的浓度下物品燃烧进行了几个月的研究,认为氧气浓度低于14％时纸不会点燃,甚至不能产生火焰.蜡烛在氧浓度低于17％时,不会被点燃.氧浓度低于18％时,易燃的松木也不会燃烧.苔藓在氧浓度低于15的时候不会被点燃,氧浓度低于17％时不会燃烧.Belcher 博士认为,这个结果并没有排除氧浓度假设,炭数据测定还不能准确的探测出氧浓度降低持续大约10万年的程度.因此,反对氧理论的人们还需要在岩石中找到更多的证据.
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不太明白你所说的“氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾”。文章似乎不是讲这个，而是说以前的人们认为恐龙等古生物绝种是因为陨石的缘故，而现在有的科学家则认为是当时地球上的氧气含量骤然减少。你所说的“燃烧实验”大概就是指最后两三段提到的用燃烧后的碳成分数据来推测远古时氧气含量的做法。...

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不太明白你所说的“氧浓度下的燃烧实验和动物灭绝的氧理论之间的矛盾”。文章似乎不是讲这个，而是说以前的人们认为恐龙等古生物绝种是因为陨石的缘故，而现在有的科学家则认为是当时地球上的氧气含量骤然减少。你所说的“燃烧实验”大概就是指最后两三段提到的用燃烧后的碳成分数据来推测远古时氧气含量的做法。

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