be divide nicely, which is why we end up with uneven months of either 30 or 31 days. Except

這就是為什麼我們最終會出現30天或31天的不均勻月份。除了

for February -- the runt of the litter -- which only gets 28... except when it gets 29 and

2月的小傢伙，只有28歲... 除了29歲的時候

then the year is 366 days long.

那麼一年就是366天長。

Why does that happen? What kind of crazy universe do we live in where some years are longer

為什麼會這樣？我們生活在一個什麼樣的瘋狂的宇宙中，有些年頭比較長

than others?

比別人多？

To answer this we need to know: just what is a year?

要回答這個問題，我們需要知道：究竟什麼是一年？

Way oversimplifying it: a year is the time it takes Earth to make one trip around the

過於簡化：一年是地球繞地球一圈所需的時間。

sun. This happens to line up with the cycle of the seasons.

太陽。這恰好與四季的循環相吻合。

Now, drawing a little diagram like this showing the Earth jauntily going around the sun is

現在，畫一張這樣的小圖，顯示地球繞著太陽歡快地走，就是："我的天啊！"。

easy to do, but accurately tracking a year is tricky when you're on Earth because the

很容易做到，但準確地跟蹤一年是棘手的，當你'在地球上，因為你'。

universe doesn't provide an overhead map.

宇宙不提供架空圖。

On Earth you only get to see the seasons change and the obvious way to keep track of their

在地球上，你只能看到四季的變化，而跟蹤它們的明顯方法是：

comings and goings is to count the days passing which gives you a 365 day calendar.

來來去去就是數著日子過，這就有了一個365天的日曆。

But as soon as you start to use that calendar, it slowly gets out of sync with the seasons.

但只要你開始使用那個日曆，它就會慢慢與季節不同步。

And with each passing year the gap gets bigger and bigger and bigger.

而且隨著時間的推移，差距越來越大，越來越大。

In three decades the calendar will be off by a week and in a few hundred years the seasons

三十年後，日曆會偏離一週，幾百年後，季節也會偏離。

would be flipped -- meaning Christmas celebrations taking place in summer -- which would be crazy.

將被翻轉 -- 意味著聖誕節的慶祝活動在夏天舉行 -- 這將是瘋狂的。

Why does this happen? Did we count the days wrong? Well the calendar predicts that the

為什麼會出現這種情況？難道是我們算錯了日子？嗯，日曆預測

time it takes for the Earth to go around the sun is 8,760 hours. But, if you actually timed

地球繞著太陽轉一圈的時間是8760小時。但是，如果你真的計時

it with a stopwatch you'd see that a year is really longer than the calendar predicts

用秒錶看，你會發現，一年的時間真的比日曆上預測的要長

by almost six hours. So our calendar is moving ever-so-slightly faster than the seasons actually

幾乎快了六個小時所以我們的日曆走得比季節走得更快一些

change.

變化。

And thus we come to the fundamental problem of all calendars: the day/night cycle, while

於是我們來到了所有曆法的根本問題：晝夜循環，而。

easy to count, has nothing to do with the yearly cycle.

易算，與年輪無關。

Day and night are caused by Earth rotating about its axis. When you're on the side faceing

白天和黑夜是由地球繞其軸線旋轉造成的。當你在面對地球的一側時

the sun, it's daytime and when you're on the other side it's night. But this rotation is

太陽，是白天，而當你在另一邊時，是夜晚。但這種旋轉是

no more connected to the orbital motion around the sun than a ballerina spinning on the back

繞日運動與芭蕾舞演員的背轉運動沒有任何聯繫。

of a truck is connected to the truck's crusing speed.

卡車的速度與卡車的破碎速度有關。

Counting the number of ballerina turns to predict how long the truck takes to dive in

計算芭蕾舞演員的轉身次數來預測卡車潛入的時間。

a circle might give you a rough idea, but it's crazy to expect it to be precise.

一個圓可能給你一個粗略的想法，但它'瘋狂的期望它是精確的。

Counting the days to track the orbit is pretty much the same thing and so it shouldn't be

算天數來追蹤軌道是差不多的事情，所以不應該'。

a surprise when the Earth dosen't happen to make exactly 365 complete spins in a year.

一個驚喜，當地球dosen'不發生使正好365完整的旋轉在一年。

Irritatingly, while 365 days are too few 366 days are too many and still cause the seasons

令人惱火的是，雖然365天太少，但366天太多，還是會造成季節性的

to drift out of sync, just in the opposite way.

以漂移不同步，只是方式相反。

The solution to all this is the leap year: where February gets an extra day, but only

解決所有這些問題的辦法是閏年：2月多了一天，但只是

every four years.

每四年一次。

This works pretty well, as each year the calendar is about a quarter day short, so after four

這很好用，因為每年的日曆都少了四分之一天，所以經過四次

years you add an extra day to get back in alignment.

年你多加一天的時間來重新調整。

Huzzah! The problem has been solved.

哈扎！問題已經解決了。

Except, it hasn't.

只是，它沒有'。

Lengthening the calendar by one day every four years is slightly too much, and the calendar

每四年加長一天的歷法，略顯過頭，曆法

still falls behind the seasons at the rate of one day per hundred years.

仍以每百年一天的速度落後於季節。

Which is fine for the apathetic, but not for calendar designers who want everything to

這對冷漠的人來說很好，但對日曆設計者來說就不一樣了，他們希望所有的東西都能被設計出來。

line up perfectly.

排列完美。

To fix the irregularity, every century the leap year is skipped.

為了解決不規則的問題，每隔一個世紀就跳過一個閏年。

So 1896 and 1904 were leap years but 1900 wasn't.

所以1896年和1904年是閏年，但1900年不是。

This is better, but still leaves the calendar ever-so-slightly too fast with an error of

這樣更好，但還是會讓日曆的速度稍稍過快，誤差為

1 day in 400 years.

400年中的1天。

So an additional clause is added to the skip the centuries rule that if the century is

所以在跳過世紀規則中增加了一個附加條款，如果世紀是

divisible by 400, then it will be a leap year.

除以400，則為閏年。

So 1900 and 2100 aren't leap years, but 2000 is.

所以1900年和2100年不是閏年，但2000年是。

With these three rules, the error is now just one day off in almost eight thousand years

有了這三條規則，現在近八千年來，誤差只差一天。

which the current calendar declares 'mission accomplished' and so calls it a day.

目前的日曆宣佈'任務完成了&39;，並以此作為一天。

Which is probably quite reasonable because eight thousand years ago humans were just

這可能是相當合理的，因為八千年前的人類還僅僅是...

figuring out that farming might be a good idea and eight thousand years from now we'll

想出了農業可能是一個好主意，八千年後，我們';會。

be hopefully be using a calendar with a better date tracking system.

希望能使用一個更好的日期跟蹤系統的日曆。

But perhaps you're a mathematician and a 0.0001 percent error is an abomination in your eyes

但也許你'是個數學家，0.0001%的誤差在你眼裡是個可惡的東西。

and must be removed.

並且必須拆除。

"Tough luck" says The Universe because the length of a day isn't even constant. It randomly

"Tough luck"宇宙說，因為一天的長度甚至不是恆定的。它隨機地

varies by a few milliseconds and on average and very slowly decreases by about 1 millisecond

以幾毫秒的速度變化，平均而言，非常緩慢地減少約1毫秒。

per hundred years. Which means it's literally impossible to build a perfect calendar that

每一百年。這意味著它的字面上不可能建立一個完美的日曆，即

lasts forever.

永遠持續下去。

In theory the length of a day will expand to be as long as a curent month -- but don't

理論上講，一天的長度將擴大到和一個月一樣長--但不要。

worry in practice it will take tens of billions of years, and our own expanding sun will destroy

擔心在實踐中需要幾百億年的時間，我們自己膨脹的太陽會毀滅。

the earth long before that happens.

在這之前，地球早已。

Sorry, not quite sure how we got from counting the days of the months to the fiery unavoidable

對不起，不太清楚我們是怎麼從數月的日子到火熱的不可避免的日子的

end of all human civilization -- unless of course we have an adequately funded space

所有人類文明的終結 -- 當然，除非我們有足夠的資金支持的空間。

program (hint, hint) -- but there you have it.

程序（提示，提示） -- -- 但你有了。

For the next eight millennia Leap years will keep the calendar in sync with the seasons

在接下來的八千年裡，閏年將使日曆與季節同步。

but in a surprisingly complicated way.

但方式卻複雜得出奇。

You can learn a lot more about orbits, different kinds of years and supermassive black holes

你可以瞭解更多關於軌道、不同類型的年份和超大品質黑洞的知識。

and over at Minute Physics. As always, Henry does a great job of explaining it all in his

和在Minute Physics。一如既往，Henry在他的文章中做了很好的解釋。

new video. Check it out.�

新視頻。看看吧。