地球白天时间越来越长 670万年增加1分钟

Earth's days are getting longer but you're not likely to notice any time soon — it would take about 6.7 million years to gain just one minute, according to a study published last Wednesday.

据上周三公布的一份报告显示，地球的白天时间正在变得越来越长，不过人类很难感觉到--因为大约要等670年才增加1分钟。

Over the past 27 centuries, the average day has lengthened at a rate of about +1.8 milliseconds (ms) per century, a British research team concluded in the journal Proceedings of the Royal Society A.

据英国一研究团队在《英国皇家学会学报》上发布的报告称，在最近的27个世纪里，每个世纪的白昼平均延长了大约1.8毫秒。

This was "significantly less", they said, than the rate of 2.3 ms per century previously estimated — requiring a mere 5.2 million years to add one minute.

该小组的研究人员明确指出，这“大大少于”之前被认为的每个世纪增加2.3毫秒。人们当时认为“只”需520万年就会增加一分钟。

"It's a very slow process," study lead co-author Leslie Morrison, a retired astronomer with Royal Greenwich Observatory, told AFP.

报告的作者之一、皇家格林尼治天文台退休天文学家莱斯.莫里森向法新社透露："这是一个非常缓慢的过程"。

"These estimates are approximate, because the geophysical forces operating on the earth's rotation will not necessarily be constant over such a long period of time," he specified. "Intervening Ice Ages etcetera will disrupt these simple extrapolations."

他解释说，"这个预估只是相近的，因为推动地球自转的力量在如此长的一段时间内并非一成不变。冰河时代的干预等其他因素会打破这些简单的推理。"

The previous 2.3 ms estimate had been based on calculations of the moon's known earth-braking forces, causing the ocean tides.

之前估算的2.3秒的结果就是基于已知的月球引力引起海洋潮汐来预估的。

Factors which influence the earth's rotation include the moon's braking effect, earth's altering shape due to shrinking polar ice caps since the last Ice Age, electro-magnetic interactions between the mantle and core, and changes in the mean sea level, said the team.

该团队表示，影响地球转动的因素包括月球的制动力，自冰河世纪以来极地冰川消融造成的地球形状的改变，地幔和地核的电磁相互作用以及海平面的变化等。