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第126期:什么是年?

來源:可可英語 編輯:Melody ?  可可英語APP下載 |  可可官方微信:ikekenet

With all the talk these days about "leaping years,"

最近人們都在討論閏年

we should probably be asking "what is a year, anyway?"

那么年是什么呢

Ignoring all cultural history,

拋開文化背景不談

a year is basically the period of time that it takes for one physical body to orbit another.

一年是一個星體環繞另一個星體一周的時間

So an earth month could equally be called a "moon year."

所以地球上一個月就是一個"月球年"

But to under-simplify things, even if we stay on earth, there are several different ways to define a year

但即使我們在地球上 一年還是有幾種不同的定義

download.jpg

— either the time it takes for the tilt of the earth's axis to come back to the same angle relative to the sun

地球的同一面兩次面向太陽之間的時間

called a tropical year

稱為"回歸年"

— or the amount of time before we come back and see the same stars rising behind the sun

或是以恒星為參照 地球再次回到對恒星相同的位置所需的時間

called a sidereal year - pronounced like ethereal

稱為恒星年

— or, since the earth follows an elliptical orbit which precesses,

因為地球是以橢圓軌道繞太陽運行

we could measure the amount of time between closest approaches to the sun

我們還可以測出地球兩次經過近日點所需的時間

this is called the anomalistic year.

這稱作近點年

Of course, all three "years" have slightly different lengths.

當然 這三種方法算出的年的長度略有不同

But our day-to-day civil calendar does its best to follow the tropical year,

但我們日常采用的是回歸年

since its duration is defined by the tilt of the earth's axis which also determines the passage of the seasons.

因為地球面向太陽的方向不同 也就形成了四季

There are non-earth years, too:

另外 還有非地球年

Mercury's year is roughly 88 earth days, Neptune's is 165 earth years,

水星年相當于88個地球日 海王星年則有165個地球年

and the "Galactic" year

至于銀河年

– which is how long the whole solar system takes to orbit once around the Milky Way –

也就是太陽系繞銀河系一周的時間

is around a quarter of a billion earth years!

需要大約2.5億年

But not all galactic years are long:

但不是所有恒星的銀河年都很長

check out this timelapse of stars orbiting the supermassive black hole at the center of the Milky Way!

上面這張圖是銀河系中心的恒星圍繞黑洞運行的圖像

Even though you can't see the black hole, it's pretty obvious that it's there,

雖然你看不到黑洞 但很明顯它就在中間

what with all those stars zipping around in orbits taking only ten earth years!

這些恒星只需要10個地球年就能公轉一周

Astrophysicists have even used these orbits

天體物理學家甚至利用這些圖像

to figure out that the black hole is as massive as 4 million suns.

算出中心黑洞的質量大約是太陽的400萬倍

But enough about interstellar timekeeping…

關于恒星年就說到這

if you want to learn more about leap years here on Earth,

如果你想了解更多關于"閏年"的知識

check out Grey's new video over on his awesome channel, "cgpgrey"

去搜"cgpGRAY"頻道

And a big thanks to the UCLA Galactic Center for doing sweet supermassive black hole research with the Keck telescope in Hawai'i,

最后感謝加州大學洛杉磯分校銀河研究小組對黑洞所做的研究

and for sharing their images with the public.

以及他們提供的圖像

重點單詞   查看全部解釋    
axis ['æksis]

想一想再看

n. 軸,中樞

 
define [di'fain]

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v. 定義,解釋,限定,規定

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duration [dju'reiʃən]

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n. 持續時間,期間

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obvious ['ɔbviəs]

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adj. 明顯的,顯然的

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check [tʃek]

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n. 檢查,支票,賬單,制止,阻止物,檢驗標準,方格圖案

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measure ['meʒə]

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n. 措施,辦法,量度,尺寸
v. 測量,量

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sidereal [sai'diriəl]

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adj. 恒星的

聯想記憶
calendar ['kæləndə]

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n. 日歷,月歷,日程表
vt. 把 ...

聯想記憶
tropical ['trɔpikəl]

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adj. 熱帶的,炎熱的,熱帶植物的

 
massive ['mæsiv]

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adj. 巨大的,大規模的,大量的,大范圍的

 
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