沉积物记录证实，木星和金星每405000年会将地球轨道从几乎圆形到明显椭圆形来回改变一次。

撰文\播音：克里斯托弗·因塔利亚塔（Christopher Intagliata）

翻译：邱燕宁

校对：张艺箫

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.

太阳的引力和发出的光线对地球产生了巨大并且明显的影响。然而其他天体也会对地球产生一些影响。

"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."

“我们在太阳系中并不孤单，太阳系中还有其他行星。当我们绕太阳转时，那些其他行星以及我们的卫星月球都在影响我们的轨道。”罗德斯大学和哥伦比亚大学拉蒙特-多尔蒂（Lamont-Doherty）地球观测站的地质学家丹尼斯·肯特（Dennis Kent）说。

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，行星科学家早就做出了金星和木星会通过挤压使得地球轨道以405000年为周期在圆形和椭圆形之间来回移动的假设。当地球按椭圆轨道运行时，距太阳的距离变化较大，地球上四季的差异会比按圆形轨道运行时更为明显。问题是，很难证明轨道形状存在这种振荡这种假设。

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.  

但肯特和他的同事们想出了一个方法，往地球的深处挖掘。他们从东海岸取了一个有极好的沉积物记录的岩芯，沉积物记录可作为极端季节性变化的证据。他们将这个岩芯和另一个来自亚利桑那州含有锆石的样本进行比较。锆石含有大量铀的痕迹，而这些铀以可预测的方式衰变，这意味着亚利桑那州的岩芯样本可以根据铀的含量来确定年代。

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他们能够按序排列，而且亚利桑那州东海岸的岩芯样本可以提供古洪水和干旱发生的时间线。

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. [Dennis V. Kent et al., Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years]

所有这些证据都证实了数值模拟试验的结果：木星和金星的确在推动着我们地球，并因此在数千年的时间里，缓慢地改变了我们的轨道。详情发表在Proceedings of the National Academy of Sciences上。

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

肯特说，这一发现也为解释地球上生命的历史提供了一种新的方式。

"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."

“这是一个钟。通过这个精确的天文钟，我们可以把各种现象联系起来，比如物种的事件，或者各种生命形式的散布。它让我们看到这些过程，并试图理解是什么驱使他们（发生）。”

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

至于现代人类是否需要担心这周期405000年的振荡？

"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. 

“这可能是一件不太值得关注的事情。我们在大气中排放了多少二氧化碳才是一个更直接的关注点。“因为尽管我们的行星邻居竭尽全力，但是我们的地球轨道在我们观测到气候变化时几乎没有变化。