此文选自听力文摘
Years Ago, The Year Was 400 Days Long
Don: Yayeumll, do you notice the days changing length over the course of the year?
Yayeumll: Sure, Don, it stays light later in the summer and gets dark earlier in the winter.
Don: No, that’s not it. I mean the whole day feels longer.
Yayeumll: I’m not sure that’s possible, Don aren’t days always 24 hours long?
Earth’s Rotation
Well, it actually takes 23 hours, 56 minutes, and 4 seconds for the Earth to rotate on its axis. But in fact the Earth’s rotation is slowing down all the time because of the gravitational pull of the moon.
Does this mean that the days really do feel longer? Nope. The moon slows us down by about two milliseconds a century, so that even 1 million years ago days were only twenty seconds shorter.
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.
400 Days Per Year
What you really would have noticed is that the time it takes the Earth to get around the sun hasn’t changed, so that back then there were 400 days a year.
Scientists have found fossil evidence from tropical corals that existed at that time, and they have about 400 daily growth rings per year. So someone was enjoying all those extra sunny days.
多年前，一年长达400天
东：雅瑶，你有注意到一年中每一天的长度在改变么？
雅瑶：当然了，东，夏天白天长些，冬天天黑得早些。
东：不，我说的不是这件事。我的意思是一整天感觉变长了些。
雅瑶：我不确定它是不是真的，东，难道一天不总是24个小时么？
地球自转
其实，实际上，地球绕地轴自转一周需要23小时56分零4秒。但实际上，因为有月球的万有引力作用，地球自转一直在变慢。
这就意味着一天真让人觉得变长了？不。每过一个世纪，月球使我们慢了2毫秒。因此，即使比起一百万年前的某一天，现在也仅仅慢了20秒。
人们会注意到么？
我不认为我能注意到。
可能不是一百万年前，而是4亿年前的某一天，当时一天长21.5小时，这样你可能就能注意到。
一年400天
你真正能意识到的是：地球绕着太阳公转的时间没有改变，所以那时一年有400天。
从存活在那时的热带珊瑚中，科学家已经发现了化石证据。它们每年大约有400个生长日轮。所以过去的人能享受这些多出来的艳阳天。
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