一年曾有400天

钱润荷

A： Do you notice the days changing length over the course of the year？

B： Sure， it stays light later in the summer and gets dark earlier in the winter.

A： No， thats not it. I mean the whole day feels longer.

B： Im not sure thats possible. Arent days always 24 hours long？

A： 你注意到了一年中每一天的长度都在改变吗？

B： 当然了，夏季白天更长，冬季天黑得更早。

A： 不，我不是说的这个。我的意思是整个一天的时间感觉变长了。

B： 我不太确定这是否可能。难道一天不是一直都是24个小时吗？

Earths Rotation

Well， it actually takes 23 hours， 56 minutes， and 4 seconds for the Earth to rotate （自转） once. But in fact the Earths rotation is slowing down all the time because of the gravitational pull （万有引力） of the moon.

Does this mean that the days really do feel longer？ No. The moon slows us down by about two milliseconds （毫秒） a century， so that even one million years ago days were only twenty seconds shorter.

地球自转

事实是，地球自转一周需要23小时56分零4秒。但实际上，由于有月球的万有引力作用，地球的自转一直在变慢。

这是就意味着一天的时间真的让人觉得变长了？不。月球每过一个世纪就让我们变慢了两毫秒。因此，即使是一百万年前，每天时间比起现在也只变短了20秒。

Would People Notice？

I doubt I would have noticed that.

Maybe not a million years ago but 400 million years ago， days were 21 and a half hours long， which you would have noticed.

人们会注意到么？

我很怀疑我是否能注意到。

也许，不是一百万年前而是4亿年前的话，当时一天是21.5小时，这样你就注意到了。

400 Days per Year

What you really would have noticed is that the time it takes the Earth to get around the sun hasnt changed， so that back then there were 400 days a year.

Scientists have found fossil （化石） evidence from tropical corals （热带珊瑚虫） that existed at that time， and they have about 400 daily growth rings per year. So someone was enjoying all those extra （额外的） sunny days.

一年400天

可能你真正意识到的是：地球绕着太阳公转的时间没有改变，所以那个时候一年有400天。

从存活于那个时候的热带珊瑚虫的化石中，科学家已经发现了证据。那个时候的珊瑚每年大约有400个生长日轮。所以那时的某个人可以享受这些额外的灿烂阳光。