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科学美国人60秒:木星和金星挤压地球的轨道

kira86 于2018-05-16发布 l 已有人浏览
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除了地球绕着太阳转之外,还有其它行星也在围着太阳转,而金星和木星每40.5万年挤压地球轨道一次。
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木星金星地球.jpg
Jupiter and Venus Squeeze Earth's Orbit

木星和金星挤压地球的轨道

The sun exerts an enormous and obvious influence on the Earth, with its gravity and light. But other bodies also have a small say in our affairs.

太阳以其重力和光线对地球产生巨大而明显的影响。但其他行星对我们的各方面也有一点发言权。

We're not alone in the solar system, there are other planets." Dennis Kent, a geologist at Rutgers University, and Columbia's Lamont–Doherty Earth Observatory. And as we circle the sun, those other planets and also our moon exert effects on our orbit."

“罗德斯大学的地质学家丹尼斯·肯特和哥伦比亚大学的拉蒙-多哈堤地球观测站表示:“在太阳系我们并不孤单,因为太阳系里还有其他行星。当我们绕着太阳转时,其他的那些行星以及我们的月球也在影响我们的轨道。”

In fact, planetary scientists have long hypothesized that Venus and Jupiter squeeze the Earth's orbit from circular to elliptical and back every 405,000 years. During an elliptical orbit, when the distance from the sun varies more, the differences between the seasons would be more extreme than when the orbit is virtually circular. Problem is, it's been hard to verify that this oscillation between orbit shapes exists.

事实上,行星科学家早就曾假设过,金星和木星每40.5万年挤压地球轨道一次,将地球的轨道从圆形挤压成椭圆形,然后又挤压回圆形。在地球轨道为椭圆形期间,地球与太阳的距离差异更大,比起地球轨道几乎为圆形时,季节之间的差异更极端。而问题是,很难证实这种轨道形状之间的振荡是否存在。

But Kent and his colleagues came up with a way - by boring down into the Earth. They took a rock core from the east coast, which has excellent sediment records - good evidence of extreme seasonal variations. They compared that core with another from Arizona, embedded with zircons. The zircons contain trace amounts of uranium, which decays in a predictable way - meaning the Arizona core could thus be dated based on uranium content.

但肯特和他的同事,想出了进一步了解地球的方法。他们从东海岸采集了一块岩芯,岩芯具有极好的沉积物记录,这些沉积物就是极端季节变化的有力证据。他们将这块岩心与采自亚利桑那州镶嵌有锆石的岩芯相比较。锆石中含有微量的铀,而铀的衰减方式是可测的,这就意味着这块采自亚利桑那州的岩芯的年代可以通过铀含量判断出来。

Magnetic information in both cores allowed them to be lined up - and the Arizona dates then provided a timeline for the ancient floods and droughts embedded in the east coast core.

两个岩芯中的磁性信息,使得两块岩芯可以并列而谈,对采自亚利桑那州的岩芯所断定的年代,为采自东海岸那块饱受古洪水和干旱洗礼的那块岩芯提供了一条时间线。

And all that evidence confirmed the mathematical simulations: Jupiter and Venus do push us around, and thus slowly alter our orbit over hundreds of millennia. The details are in the Proceedings of the National Academy of Sciences.

所有这些证据都证实了这一数学模拟试验结果:木星和金星确实在把我们推来挤去,并因此在数十万年的时间里,缓慢地改变了我们的轨道。详情请见《美国国家科学院院刊》。

Kent says the discovery also provides a new way to interpret the history of life on the planet.

肯特说,这一发现还为解释地球生命史提供了一种新方式。

It's a clock. And so being able to have a precise chronometer we can relate things like speciation events, or dispersals of various life forms. It allows us to look at these things and try to understand what's driving them.

“这是一个时钟,所以能够拥有一个精确的计时表,我们可以将诸如物种形成事件或各种生命形式的分布联系起来。这样,我们就可以观察这些事物,并试着了解其被驱使的因素。

As for whether modern-day humans need to worry about this 405,000-year oscillation?

那么现代人类是否需要担心这个40.5万年一次的振荡呢?

This is probably pretty low down the list of things to be concerned about. How much CO2 we're putting in the atmosphere, that's of a more immediate concern. Because, despite our planetary neighbors' best efforts, our orbit has barely budged as we've observed our climate change.

“这事发生的概率相当低,我们需要关注的事情很多,比如我们在大气中排放了多少二氧化碳,这才是当务之急。”因为尽管临近地球的行星倾尽全力,但就所观察到的气候变化看来,我们的轨道几乎纹丝未动。

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