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什么是闰年 – 译学馆
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什么是闰年

What is a Leap Year?

A calendar year is made of three hundred and sixty five days
公历一年有365天
— a number that refuses to be divided nicely,
这数字不能平均分
which is why we end up with uneven months of either 30 or 31 days.
所以我们只能不均匀地把每个月分成30或31天
Except for February — the runt of the litter — which only gets 28…
除了二月天数最少 只有28天
except when it gets 29 and then the year is 366 days long.
但如果是闰年 二月就有29天
Why does that happen?
为什么会这样呢
What kind of crazy universe do we live in
我们生活在怎样一个疯狂的宇宙中
where some years are longer than others?
有些年比其他长
To answer this we need to know: just what is a year?
要回答这个问题 我们要明白“一年”的含义
Way oversimplifying it: a year is the time it takes Earth to make one trip around the sun.
简言之 一年就是地球绕太阳一周的时间
This happens to line up with the cycle of the seasons.
这正好符合季节的循环
Now, drawing a little diagram like this showing
现在 如图所示
the Earth jauntily going around the sun is easy to do,
地球绕太阳蹦哒一周很容易
but accurately tracking a year is tricky when you’re on Earth
但你要在地球上追踪一年很难
because the universe doesn’t provide an overhead map.
因为宇宙不会给你上帝视角
On Earth you only get to see the seasons change
你在地球上只能看见季节更替
and the obvious way to keep track of their comings and goings
追踪季节最明显的方法就是数日子
is to count the days passing which gives you a 365 day calendar.
也就得到了一年365天的日历
But as soon as you start to use that calendar,
然而 你一旦开始使用这日历
it slowly gets out of sync with the seasons.
慢慢地 你就不能与季节变换同步
And with each passing year
而且 随着每一年逝去
the gap gets bigger and bigger and bigger.
差距会变得越来越大
In three decades the calendar will be off by a week
每隔30年 日历就会落后一周
and in a few hundred years the seasons would be flipped
只要几百年 季节就会颠倒
— meaning Christmas celebrations taking place in summer
也就是说 你会在夏天过圣诞节
— which would be crazy.
这太疯狂了
Why does this happen?
为什么会这样?
Did we count the days wrong?
我们数错日子了吗
Well the calendar predicts that the time it takes for the Earth to go around the sun is 8,760 hours.
日历预测 地球绕太阳一周需要8760小时
But, if you actually timed it with a stopwatch
但要是你用表实际测一下
you’d see that a year is really longer than the calendar predicts by almost six hours.
你就会发现 一年的时间确实比日历上大约多6个小时
So our calendar is moving ever-so-slightly faster
所以我们的日历比实际的
than the seasons actually change.
季节更替要稍微快一点
And thus we come to the fundamental problem
再回到所有日历的基本问题
of all calendars: the day/night cycle,
昼夜交替
while easy to count, has nothing to do with the yearly cycle.
这很容易记录 因为它与年的循环无关
Day and night are caused by Earth rotating about its axis.
白天和黑夜是由地球自转引起的
When you’re on the side faceing the sun, it’s daytime
当你在向阳面时 就是白天
and when you’re on the other side it’s night.
当另一边就是晚上
But this rotation is no more connected to the orbital motion around the sun
但是自转与绕太阳公转没有联系
than a ballerina spinning on the back of a truck
就像舞者在车上旋转的速度
is connected to the truck’s crusing speed.
其实跟车速无关
Counting the number of ballerina turns
靠数舞者旋转的次数
to predict how long the truck takes to dive in a circle might give you a rough idea,
或许能大概估算出车跑一圈的时间
but it’s crazy to expect it to be precise.
但别指望这能多精确
Counting the days to track the orbit is pretty much the same thing
数着天数去判断地球公转也一样
and so it shouldn’t be a surprise when the Earth dosen’t happen to make exactly 365 complete spins in a year.
所以地球不能在一年内转365圈也不稀奇
Irritatingly, while 365 days are too few 366 days are too many
烦人的是 365天太少 366天太多
and still cause the seasons to drift out of sync, just in the opposite way.
而且 会以两种相反的方法使季节不能同步
The solution to all this is the leap year:
闰年就是解决办法
where February gets an extra day, but only
闰年二月加一天
every four years.
但每四年才加一次
This works pretty well, as each year the calendar is about a quarter day short, so after four
这方法很好 因为日历上每年会短1/4天
years you add an extra day to get back in alignment.
每四年多加一天就能让季节与时间保持一致
Huzzah!
好哇
The problem has been solved.
问题解决了
Except, it hasn’t.
实际上并没有
Lengthening the calendar by one day every four years is slightly too much,
每四年加一天起到的作用很小
and the calendar still falls behind the seasons at the rate of one day per hundred years.
每一百年过去 日历上仍会落后一天
Which is fine for the apathetic,
对不关心这个问题的人来说没啥大不了
but not for calendar designers who want everything to line up perfectly.
但对追求完美的日历设计者而言并不好
To fix the irregularity, every century the leap year is skipped.
为了解决该问题 每一百年就跳过一个闰年
So 1896 and 1904 were leap years but 1900 wasn’t.
所以1896和1904是闰年但1900就不是
This is better,
现在好多了
but still leaves the calendar ever-so-slightly too fast with an error of 1 day in 400 years.
但日历每四百年仍会快一天
So an additional clause is added to the skip the centuries rule
为解决这个问题 我们又加了一个规定
that if the century is divisible by 400, then it will be a leap year.
如果年份能和400整除 它就是闰年
So 1900 and 2100 aren’t leap years, but 2000 is.
所以1900和2100不是闰年 但2000年是
With these three rules, the error is now just one day off in almost eight thousand years
有了这三项规定 现在的误差只有八千年慢一天
which the current calendar declares ‘mission accomplished’
当前日历的任务已经完成
and so calls it a day.
那就这么定了
Which is probably quite reasonable
或许这也挺合理的
because eight thousand years ago humans were just figuring out that farming might be a good idea
毕竟八千年前的人类才刚开始农耕
and eight thousand years from now
而从现在起的八千年后
we’ll be hopefully be using a calendar with a better date tracking system.
希望我们使用的日历能更好地与时间同步
But perhaps you’re a mathematician
要是你是个数学家
and a 0.0001 percent error is an abomination in your eyes
连十万分之一的误差都无法容忍
and must be removed.
一定要除掉
“Tough luck” says The Universe because the length of a day isn’t even constant.
宇宙对你说 那真惨 因为每一天的时间实际都不同
It randomly varies by a few milliseconds
每天的时间以毫秒为单位随机变化
and on average and very slowly decreases by about 1 millisecond per hundred years.
而且平均以每百年慢一毫秒的速度缓慢减少
Which means it’s literally impossible to build a perfect calendar that lasts forever.
这意味着 我们几乎不可能创建一个完美日历
In theory the length of a day will expand to be as long as a curent month
理论上 一天可以延长至现在一个月
— but don’t worry. In practice it will take tens of billions of years,
但无需担心 那需要很久才会实现
and our own expanding sun will destroy
而在那发生之前
the earth long before that happens.
不断膨胀的太阳早已毁灭了地球
Sorry, not quite sure how we got from counting the days of the months
不好意思 我们怎么就从数日期
to the fiery unavoidable end of all human civilization
说到了到人类文明不可避免的终结
— unless of course we have an adequately funded space program (hint, hint)
除非我们有一个资金充足的太空计划
— but there you have it.
这就是有关闰年的知识
For the next eight millennia Leap years will keep the calendar in sync with the seasons
接下来八千年 日历能与季节同步
but in a surprisingly complicated way.
但是它们同步的方式极其复杂
You can learn a lot more about orbits, different kinds of years
你可以在《分钟物理》了解更多关于轨道
and supermassive black holes and over at Minute Physics.
不同年份和超大质量黑洞的知识
As always, Henry does a great job of explaining it all in his new video.
像往常一样 Henry在新视频中很好地解释了一切
Go check it out.
快去看看吧

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如果你和我一样执着于二月份究竟有28天还是29天的话,不妨点击这里,这里或许有你想要的答案

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视频来源

https://www.youtube.com/watch?v=xX96xng7sAE

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