Despite the salacious title, nudity is not required.

儘管標題看起來有點問題 但是你並不需要裸體

In fact, given that a lot of astronomical observations are done at night, you may want to bundle up.

事實上 因為大多數的天文觀測都在晚上 你或許應該多穿一些

[Theme Music] "One giant leap for mankind"

[背景音樂] '(我的一小步)是人類的一大步'

As it relates to astronomy, “naked eye” means no binoculars, no telescope.

在天文學上 裸眼的意思是 不用雙筒,單筒望遠鏡

Just you, your eyeballs, and a nice, dark site from which to view the heavens.

只要你、你的眼睛和一個晴朗的夜晚來窺探蒼穹

After all, that’s how we did astronomy for thousands of years,

畢竟 那就是幾千年來我們觀測天文的方法

and it’s actually pretty amazing what you can figure out about the Universe just by looking at it.

而且這其實很神奇，我們可以透過盯著它看來得知很多天文學的事情

Imagine you’re somewhere far away from city lights, where you have an unobstructed view of the cloudless sky.

想像一下 你在一個遠離城市的地方 擁有一個不受屏障的視野來仰望星空

The Sun sets, and for a few minutes you just watch as the sky darkens.

太陽下山了 花個幾分鐘看著天空暗下來

Then, you notice a star appear in the east, just over a tree.

這時 你發現有一顆星星出現在東方 在一棵樹梢

Then another, and another, and within an hour or so you are standing beneath an incredible display,

這裡也有! 那裏也有! 然後大約一個小時之後 你就會發現 你正站在一個不可思議的景象之下

the sky spangled with stars.

天空中布滿了星星

What do you notice right away? First, there are a lot of stars.

你會先發現什麼事? 首先 天上有很多的星星

People with normal vision can see a few thousand stars at any given time, and if you want a round number,

一個有正常視力的人可以在任何時間看見大約幾千顆的星星─如果你想要一個大約的數字

there are very roughly six to ten thousand stars in total that are bright enough to detect by eye alone,

那大約有6000~10000顆星星是亮到足以被眼睛看到

depending on how good your sight is.

端看你的視力好壞

The next thing you’ll notice is that they’re not all the same brightness.

第二件事情是:它們的亮度並不相同

A handful are very bright, a few more are a bit fainter but still pretty bright, and so on.

有些非常亮 較多的雖然暗了點但還是頗亮─依此類推

The faintest stars you can see are the most abundant, vastly outnumbering the bright ones.

你所能看得到最暗的星星是天空中 最常見 也是最多的一種

This is due to a combination of two effects.

這是因為兩個因素共同的影響

One is that stars aren’t all the same intrinsic, physical brightness.

第一點是: 它們本質上就不是同樣的亮度

Some are dim bulbs, while others are monsters, blasting out as much light in one second as the Sun does in a day.

有些只是微弱的小燈泡 有些像怪物一樣 一秒內放出的能量跟太陽在一天之內放出的一樣多

The second factor is that not all stars are the same distance from us.

第二個因素是: 不是所有的星星跟我們的距離都相等

The farther away a star is, the fainter it is.

一個星星距離我們愈遠 看起來就愈暗

Interestingly, of the two dozen or so brightest stars in the sky, half are bright because they’re close to Earth,

有趣的是 在大約兩打的亮星之中有一半是因為距離地球比較近所以看起來比較亮

and half are much farther away but incredibly luminous, so they still appear bright to us.

另一半則是離我們比較遠但是不可思議的亮 所以看起來還是很亮

This is a running theme in astronomy, and science in general.

這在天文學或甚至是科學裡面都是一種常態

Some effects you see have more than one cause.

有些你看到的現象有兩個以上的成因

Things aren’t always as simple as they seem.

事情並不都如所見的簡單

The ancient Greek astronomer Hipparchus is generally credited for creating the first catalog of stars,

一般認為古希臘天文學家伊巴谷是最早記錄星表的人

ranking them by brightness.

透過亮度來分類

He came up with a system called magnitudes, where the brightest stars were 1st magnitude,

他創造了一個東西叫星等 最亮的星被稱作一等星

the next brightest were 2nd magnitude, down to 6th magnitude.

第二亮的叫二等星 一直記錄到六等星

We still use a variation of this system today, thousands of years later.

幾千年後的今天我們仍然在使用類似的系統

The faintest stars ever seen (using Hubble Space Telescope) are about magnitude 31 –

人類所見最暗的星(透過哈伯太空望遠鏡)大約是31等星

the faintest star you can see with your eye is about 10 billion times brighter!

你所能看到最暗的星星大約比他亮幾百億倍!

The brightest star in the night sky — called Sirius, the Dog Star —

天空中最亮的星─天狼星(狗星??)

is about 1000 times brighter than the faintest star you can see.

大約比你所能看到最暗的星亮個1000倍

Let’s take a closer look at some of those bright stars, like, say, Vega.

讓我們來仔細觀察其中一顆數一數二亮的星 像是織女星

Notice anything about it? Yeah, it looks blue. And Betelgeuse looks red.

發現了什麼嗎?它看起來是藍色的!而參宿四看起來是紅的

Arcturus is orange, Capella yellow. Those stars really are those colors.

大角星是橘色 五車二是黃的 那些星星真的就是那種顏色

By eye, only the brightest stars seem have color, while the fainter ones all just look white.

肉眼來看 最亮的星星看起來有顏色 比較暗的看起來是白色

That’s because the color receptors in your eye aren’t very light-sensitive,

那是因為你眼睛裡的感光細胞不是那麼的靈敏

and only the brightest stars can trigger them.

唯有最亮的星星才能觸發它們

Another thing you’ll notice is that stars aren’t scattered evenly across the sky.

另一個你會發現的事情是 星星並不是均勻的分布在天空中

They form patterns, shapes.

它們聚集成圖案 形狀

This is mostly coincidence, but humans are pattern-recognizing animals,

這大多是巧合 但是人類是很會辨識圖像的動物

so it’s totally understandable that ancient astronomers divided the skies up into constellations

所以我們可以完全體會古代的天文學家把天空分割成星座

(literally sets or groups of stars), and named them after familiar objects.

真的就是一組一組的星星 然後用熟悉的東西來命名

Orion is probably the most famous constellation;

獵戶座大概是最有名的星座

it really does look like a person, arms raised up, and most civilizations saw it that way.

它看起來真的很像一個人舉著手臂─大多數的文明皆是如此

There’s also tiny Delphinus; it’s only 5 stars, but it’s easy to see it as a dolphin jumping out of the water.

還有小小的海豚座 只由五顆星組成 但是很容易看出一隻海豚跳出水面

And Scorpius, which isn’t hard to imagine as a venomous arthropod.

天蠍座─並不難看出來是一隻有毒的節肢動物(蠍子)

Others, well, not so much. Pisces is a fish? Yeah, OK. Cancer is a crab? If you say so.

其它的嗎....就不是那麼容易了 雙魚座是魚?好吧 巨蟹座是隻螃蟹?!如果你要這樣看的話

Although they were rather arbitrarily defined in ancient times, today we recognize 88 official constellations,

雖然它們是由古代人任意的定義出來的 到現在我們認定88個官方的星座

and their boundaries are carefully delineated on the sky.

而且他們的邊界是很仔細劃分出來的

When we say a star is in the constellation of Ophiuchus,

當我們說一顆星星位在蛇夫座

it’s because the location of the star puts it inside that constellation’s boundaries.

那是因為那顆星星在天上的位置剛好在蛇夫座的範圍內

Think of them like states in the US:

把邊界想像成是美國的州

the state lines are decided upon by mutual agreement, and a city can be in one state or the other.

州之間的邊界是雙方同意的劃分 一個城市可以在這個州內或是在另一個裡面

Mind you, not every group of stars makes a constellation.

順帶提醒 並不是所有聚集的星星都會被認為是星座

The Big Dipper, for example, is only one part of the constellation of Ursa Major, the Big Bear.

例如北斗七星就只是大熊座的一部分

The bowl of the dipper is the bear’s haunches, and the handle is its tail.

勺子的部分是熊的臀部 柄則是尾巴

But! Bears don't have tails!

但是 熊沒有尾巴!

So astronomers might be great at pattern recognition, but they're terrible at zoology.

天文學家或許很會認圖形 但是他們的動物學一定非常糟糕!

Most of the brightest stars have proper names, usually Arabic.

大多數的亮星有固有的名字 通常是阿拉伯語

During the Dark Ages, when Europe wasn’t so scientifically minded,

在中古時期 當歐洲並不那麼在意科學時

it was the Persian astronomer Abd al-Rahman al-Sufi who translated ancient Greek astronomy texts into Arabic,

波斯天文學家阿卜杜勒-拉赫曼·蘇菲把古希臘的典籍翻譯成阿拉伯文

and those names have stuck with us ever since.

所以那些名字一直被沿用至今

However there are a lot more stars than there are proper names, so astronomers use other designations for them.

但是還有非常多的星星沒有固有名稱 所以天文學家用其他的方法來命名它們

The stars in any constellation are given Greek letters in order of their brightness,

在星座中的星星被賦予希臘字母─依照他們的亮度來排序

so we have Alpha Orionis, the brightest star in Orion, then Beta, and so.

所以我們有獵戶座α 獵戶座中最亮的星星 然後是β 依此類推

Of course, you run out of letters quickly, too, so most modern catalogs just use numbers;

當然 你很快就會用光所有的字母 所以現代的命名法通常只用數字

it’s a lot harder to run out of those.

它們比較難被用光

Of course, just seeing all those faint stars can be tough, which brings us to this week’s “Focus On.”

理所當然的 光是觀測那些微弱的星星就很難了 也因此讓我們來到了這禮拜的"關注焦點"

Light pollution is a serious problem for astronomers.

光害對天文學家來說是一個很嚴重的問題

This is light from street lamps, shopping centers, or wherever,

這些光來自路燈 購物中心 或是任何有光線射進天空中的地方

where the light gets blasted up into the sky instead of toward the ground.

本來這些光線應該射向地面的

This lights the up the sky, making fainter objects much more difficult to see.

這些光點亮了天空 造成原本就很微弱的星星更難被觀測

That’s why observatories tend to be built in remote areas, as far from cities as possible.

這就是為什麼天文台通成會設在偏遠地方 離城市愈遠愈好

Trying to observe faint galaxies under bright sky conditions is like trying to listen to

在嚴重光害下觀測遙遠的星系就像是試著聽一個

someone 50 feet away whispering at you at a rock concert.

距離你50英呎的人在搖滾演唱會裡對你說悄悄話一樣

This affects the sky you see as well.

這同時也影響了你所看到的天空

From within a big city, it's impossible to see the Milky Way,

你根本不可能在一個大城市裡看到銀河

the faint streak of across the sky that’s actually the combined light of billions of stars.

那微弱的一帶光線是由幾十億顆恆星所組成的

It gets washed out with even mild light pollution.

只是一些些的光害就足以洗掉它

Your view of Orion probably looks like this:

你所看到的獵戶座大概長這樣

When from a dark site it looks like this:

而在一個比較暗的地方看起來是這樣

It’s not just people who are affected by this, either.

並不是只有人會受到光害的影響

Light pollution affects the way nocturnal animals hunt, how insects breed,

夜行性動物的獵食 昆蟲的繁殖跟其他的東西

and more, by disrupting their normal daily cycles.

都會因為光害打亂了牠們的日光週期而受到干擾

Cutting back light pollution is mostly just a matter of using the right kind of light fixtures outside,

通常我們只需要使用正確的照明設備就可以減少光害

directing the light down to the ground.

使光照向地面

A lot of towns have worked to use better lighting, and have met with success.

很多城鎮都開始使用更好的照明設備 並且取得良好的效果

This is due in large part to groups like the International Dark-Sky Association, GLOBE at Night, The World at Night,

這大多得歸功於像是國際暗天協會 Globe at Night, The World At Night

and many more, who advocate using more intelligent lighting, and to help preserve our night sky.

等等的組織 他們鼓吹使用智慧光源 並且幫助保存夜晚的天空

The sky belongs to everyone, and we should do what we can to make sure it’s the best possible sky we can see.

天空是大家的 而我們應該為保存一片良好的夜空盡一分力

Even if you don’t have dark skies, there’s another thing you can notice when you look up.

即使你沒有很暗的天空 還是有一些你會注意到的事情

If you look carefully, you might see that a couple of the brightest stars look different than the others.

如果你仔細看 你或許可以發現有些亮星跟其他的亮星有些不同

They don’t twinkle! That’s because they aren’t stars, they’re planets.

它們並不會閃爍 那是因為它們不是恆星 它們是行星

Twinkling happens because the air over our heads is turbulent,

閃爍的原因是因為在我們頭上的空氣會擾動

and as it blows past, it distorts the incoming light from stars,

當經過時 它們會擾動入射的星光

making them appear to slightly shift position and brightness several times per second.

使它們在一秒內看起來有些微的移動位置還有改變亮度很多次

But planets are much closer to us, and appear bigger, so the distortion doesn’t affect them as much.

但是行星距離我們比較近 看起來也比較大 所以干擾對它們影響不大

There are five naked eye planets (not counting Earth): Mercury, Venus, Mars, Jupiter, and Saturn.

天上有5顆肉眼可見的行星(不包括地球) 水星 金星 火星 木星和土星

Uranus is right on the edge of visibility, and people with keen eyesight might be able to spot it.

天王星恰好就在可見邊緣上 所以有敏銳視力的人或許可以看到

Venus is actually the third brightest natural object in the sky, after the Sun and Moon.

實際上金星是天上第三亮的自然物體 僅次於太陽和月亮

Jupiter and Mars are frequently brighter than the brightest stars, too.

木星和火星經常變得比最亮的星星還亮

If you stay outside for an hour or two, you’ll notice something else that’s pretty obvious:

如果你在外面待上幾個小時 你會發現一見蠻明顯的事

the stars move, like the sky is a gigantic sphere wheeling around you over the course of the night.

星星會移動 就像是天空是一個巨大的圓體 整晚圍繞著你轉動

In fact, that’s how the ancients thought of it.

事實上 古代人就是這麼想的

If you could measure it, you’d find this celestial sphere spins once every day.

如果你測量一下 你會發現這個天文球體一天轉動一次

Stars toward the east are rising over the horizon, and stars in the west are setting,

在東方的星星正在生起 而西邊的正在落下

making a big circle over the course of the night (and presumably, day).

在一天內產生一個巨大的圓形

This is really just a reflection of the Earth spinning, of course.

這其實只是反映出地球的自轉

The Earth rotates once a day, and we’re stuck to it,

地球一天轉動一次 而我們被固定在裡面

so it looks like the sky is spinning around us in the opposite direction.

所以看起來天空圍繞著我們已自轉的反方向轉動

There’s an interesting thing that happens because of this. Look at a spinning globe.

這造成一個有趣的現象 看一下這個轉動的地球

It rotates on an axis that goes through the poles, and halfway between them is the Equator.

它在一個穿過兩極的軸轉動 而在它們之間的則是赤道

If you stand on the Equator, you make a big circle around the center of the Earth over a day.

如果你站在赤道上 在一天的時間內你會圍繞著地球轉一圈

But if you move north or south, toward one pole or the other, that circle gets smaller.

但如果你朝南或北兩極移動 那一圈便會縮小

When you stand on the pole, you don’t make a circle at all; you just spin around in the same spot.

當你站在極上時 你不會繞那一圈 反而是在原地轉動

It’s the same thing with the sky.

對天空也是如此

As the sky spins over us, just like with the Earth, it has two poles and an Equator.

當夜空從我們頭上轉過 它具有兩極和赤道─就像地球

A star on the celestial Equator makes a big circle around the sky, and stars to the north or south make smaller ones.

一個在天球赤道的星星會產生一個圍繞著天空的大圓 而靠近南北極的星星則會產生比較小的

A star right on the celestial pole wouldn’t appear to move at all, and would just hang there,

一個剛好位在天球南北極的星星看起來並不會移動 它只會待在那

like it was nailed to that spot, all night long.

就像是它被釘在那個地方一整晚一樣

And this is just what we see! Photographic time exposures show it best.

而看到的就是如此! 長時間曝光照片最可以體現這個現象

The motions of the stars show up as streaks.

星體的移動軌跡形成線條

The longer the exposure, the longer the streaks as the stars rise and set, making their circular arcs in the sky.

曝光時間愈長 線條也就隨升起落下而拉長 形成天上的弧線

You can see stars near the celestial equator making their big circles.

你可以看到在天球赤道附近的星星形成它們的大圓圈

And, by coincidence, there’s also a middling-bright star that sits very close to the north celestial pole.

而巧合的是 在天球北極附近有一顆中等程度亮的星體

That’s called Polaris, the north or pole star.

那是北極星

Because of that, it doesn’t appear to rise or set, and is always to the north, motionless.

因為如此 它看起來並不會升起或落下 一直待在北方不動

It really is coincidence; there’s no southern pole star, unless you count Sigma Octans,

這真的是巧合 南方就沒有南極星 除非你把南極座σ算進去

a dim bulb barley visible by eye that’s not all that close to the south pole of the sky anyway.

一個勉強在肉眼可視範圍內而且距離天球南極一段距離的一顆星

But even Polaris isn’t exactly on the pole -- it’s offset a teeny bit.

但是即使是北極星也不是準確的落在天球北極 差了一點

So it does make a circle in the sky, but one so small you’d never notice.

所以它會產生一個圓圈 只是小到你分辨不出來而已

By eye, night after night, Polaris is the constant in the sky, always there, never moving.

肉眼來看 北極星是天上不變的東西 一直在那 永遠不動

Remember, the sky’s motion is a reflection of the Earth’s motion.

記住 天球的移動反映了地球的轉動

If you were standing on the north pole of the Earth, you’d see Polaris at the sky’s zenith

如果你站在地球北極上 你會發現北極星在天上的頂點

— that is, straight overhead — fixed and unmoving.

也就是說 在頭頂上 固定不動

Stars on the celestial equator would appear to circle the horizon once per day.

在天球赤道上的星星看起來會沿著地平線轉動 一天一次

But this also means that stars south of the celestial equator can’t be seen from the Earth’s north pole!

但這也表示了北極看不到天球赤道以南的星星

They’re always below the horizon.

它們永遠待在地平線下方

So this in turn means that which stars you see depends on where you are on Earth.

所以這表示你所能看到的星星會根據你的位置而改變

At the north pole, you only see stars north of the celestial equator.

在北極 你永遠只能看到在天球赤道以北的星體

At the Earth’s south pole, you only see stars south of the celestial equator.

在南極 你永遠只能看到在天球赤道以南的星體

From Antarctica, Polaris is forever hidden from view.

從南極洲來看 北極星永遠都沒辦法被看到

Standing on the Earth’s equator, you’d see Polaris on the horizon to the north,

站在赤道上 你會發現北極星位在北邊的地平線上

and Sigma Octans on the horizon to the south,

而南極座σ位在南邊的地平線

and over the course of the day the entire celestial sphere would spin around you;

而一天內 整個天球會繞過你的頭頂

every star in the sky is eventually visible.

因此天上所有的星星是可見的

While Polaris may be constant, not everything is.

北極星或許是恆定的 但其它的並不是

Sometimes you just have to wait a while to notice.

有時你只須要等一下就會看到

And to that point, you’ll have to wait a while to find out what I mean by this,

而你得等一段時間才能了解我的意思

because we’ll be covering that in next week’s episode.

因為我們會在下一集討論這個

Today we talked about what you can see on a clear dark night with just your eyes:

今天我們談到了在晴朗的夜晚肉眼所能看到的東西

thousands of stars, some brighter than others, arranged into patterns called constellations.

數以千計的星星 有些比其他的亮 排列成稱為星座的形狀

Stars have colors, even if we can’t see them with our eyes alone, and they rise and set as the Earth spins.

星星具有顏色 即使我們無法用肉眼看到 而且它們會隨著地球自轉而升降

You can see different stars depending on where you are on Earth,

你會因為位置不同而看到不同的星星

and if you’re in the northern hemisphere, Polaris will always point you toward north.

如果你站在北半球 北極星永遠會為你指向北方

Crash Course is produced in association with PBS Digital Studios.

Crash Course和PBS Digital Studios合作製播

This episode was written by me, Phil Plait.

這集節目是我,Phil Plait所寫的

The script was edited by Blake de Pastino, and our consultant is Dr. Michelle Thaller.

腳本由Blake de Pastino所編輯 而我們的顧問是Dr. Michelle Thaller

It was co-directed by Nicholas Jenkins and Michael Aranda, and the graphics team is Thought Café.

由Nicholas Jenkins和Michael Aranda聯合監製 而我們的視覺後製製作團隊是Thought Café