I've talked a lot about observing the night sky with your eyes; just simply going out and seeing what you can see.
我們已經討論了很多裸眼可以進行的星空觀測，快出門試試你能看到什麼吧。
It's pretty amazing what you can learn just by doing that, and of course that's all we humans could do for thousands of years.
僅僅這樣的所見已經非常驚人了，當然這也是人類千百年來唯一能做的。
But now we can do better.
但現在我們有更好的方式。
We can use telescopes.
使用天文望遠鏡。
The first person to invent the telescope is lost to history; despite "common knowledge," Galileo did not invent them.
雖然「常識」告訴我們伽利略發明瞭望遠鏡，但其實他沒有。
He wasn't even the first person to point one at the sky, or the first person to publish results!
第一個發明望遠鏡的人是誰已經遺失在歷史中了，而伽利略甚至不是第一個把望遠鏡指向天空的人！
But he was a loud and persistent voice over the years, and his amazing string of discoveries using his crude instrument landed him firmly in the history books.
他也不是第一個發布望遠鏡觀測結果的人，但他持續多年大力宣傳自己通過粗糙工具做出的驚人發現，這讓他被史書銘記。
Aggressive self-marketing sometimes pays off.
看來有時激進的自我宣傳是會帶來回報的。
You might think the purpose of a telescope is to magnify small objects so we can see them better.
你可能認為望遠鏡的作用是把微小物體放大，這樣我們就能更好地看到它們。
That's how a lot of telescopes are marketed, but to be honest that's not exactly the case.
這確實是很多望遠鏡的功能，但實際上並不完全如此。
If you want to be really general, the purpose of a telescope is to make things easier to see: to make the invisible visible, and to make the things already visible visible more clearly.
如果你想做一個更廣泛的定義，望遠鏡的用途是讓物體更容易被觀測：讓不可見的東西變得可見，讓已經可見的東西變得更清晰可見。
A telescope works by gathering light.
望遠鏡的工作原理是聚光。
Think of it like a bucket in the rain: the bigger the bucket, the more rain you collect.
把它想像成一個在雨中的水桶：桶越大，你收集到的雨水就越多。
If your bucket is big enough, you'll get plenty of water even when it's only sprinkling out.
如果你的水桶足夠大，即使是在濛濛細雨中，你也能得到足夠的水。
In the case of a telescope, the "bucket" is an optical device like a lens or a mirror that collects light.
對望遠鏡來說，「水桶」就是一種像透鏡單面鏡一樣收集光線的光學裝置。
We call this device the objective, and the bigger the objective, the more light it collects.
我們稱這個裝置為物鏡，物鏡越大，它收集的光就越多。
Look at your eyes. . . well, that's tough, so let's think about our eyes for a moment.
對比一下你的眼睛……呃，眼睛真是太小了，那我們就順便考慮一下眼睛。
They also work as light buckets, but they only collect light through our pupils, which even under the best of circumstances are less than a centimeter across; a very tiny bucket indeed.
它們也相當於收集光線的水桶，但它們只是通過瞳孔收集光線，而瞳孔在最大的情況下，其直徑也不到一釐米；只是一個非常小的桶。
But we can do better.
但我們有更好的選擇。
To extend the analogy, a telescope is like a bucket with a funnel at the bottom.
繼續我們的類比的話，望遠鏡就像底部是個漏鬥的水桶。
All that light that it collects is then concentrated, focused, and sent into your eye.
它收集到的所有光線都被匯聚，送入你的眼睛。
It turns a trickle of light into a torrent.
它把涓涓細流變成了奔騰的江河。
The amount of light it collects depends on the area of the objective.
它收集的光的數量取決於物鏡的面積。
That means if you double the diameter of the collector, you'd collect four times as much light, because the area of the collector goes up as the square of the radius.
這意味著如果你把收集鏡的直徑增加一倍，你就能收集到四倍的光，因為收集鏡的表面積與半徑的平方成正比。
Make a bucket 10 times wider, and you collect 100 times as much light!
同理，把一個桶放大10倍，你就能收集到100倍的光！
Clearly, as telescopes get bigger their ability to show us faint objects increases enormously.
顯然，隨著望遠鏡變得越來越大，它們向我們展示模糊物體的能力也大大增強。
In fact that was one of Galileo's first and most important discoveries: stars that were invisible to the naked eye were easily seen through his telescope, even though it only had a lens a few centimeters across.
事實上，這是伽利略最早也是最重要的發現之一：肉眼看不見的星星通過他的望遠鏡就很容易被看到，儘管它只有一個幾釐米寬的透鏡。
Those faint stars didn't emit enough light for his eyes to see them, but when he increased his collecting area with a telescope, they popped into visibility.
那些暗淡的星星發出的光不足以讓他的眼睛看到它們，但當他用望遠鏡放大了光線收集面積時，它們就突然出現在了視野之中。
The primary way telescopes work is to change the direction light from an object is traveling.
望遠鏡的主要工作方式是改變物體發出的光的運動方向。
I can see a star with my eye because light from that star is sent in my direction, into my eye.
我能通過我的眼睛看到一顆星星，是因為那顆星星發出的光射向我的方向，進入了我的眼睛。
But most of that light misses my eye, falling to the ground all around me.
但它發出的大部分光線錯過了我的眼睛，落在我周圍的大地上。
The telescope collects that light, bounces it around, and then channels it into my eye.
望遠鏡則收集這些光，把它們反射回來，然後把它們輸送到我的眼睛裡。
When the very first telescopes were built, this changing of the direction of light was done using lenses.
當第一個望遠鏡被製造出來的時候，是通過使用透鏡來改變光的方向的。
When light goes from one medium to another – say, from going through air to going through water or glass – it changes direction slightly.
當光從一種介質傳播到另一種介質時——比如說，從空氣傳播到水或玻璃中——光的方向就會發生輕微的改變。
You see this all the time; a spoon sitting in a glass of water looks bent or broken.
你經常會看到這種現象；比如一個盛水的玻璃杯中的湯勺看起來像是彎曲了或者斷了。
The spoon is doing just fine, but the light you see from it is getting bent, distorting the image.
湯勺其實完好無損，但你所看到的它反射出的光線被彎曲了，扭曲了你看到的影像。
This bending is called refraction.
這種彎曲現象叫做折射。
The way light bends depends on what's bending it (like water or glass) and the shape of the object doing the bending.
光線彎曲的方式取決於它是被什麼彎曲了(比如水或玻璃杯)，以及導致光線彎曲的物體的形狀。
It so happens that if you grind a piece of glass into a lens shape, it bends — or refracts — the incoming light in a cone, focusing it into a single spot.
如果你把一塊玻璃磨成透鏡的形狀，它就會使入射光線彎折——或者說發生折射——而形成一個圓錐型，聚焦到一個點上。
It's a light funnel!
這就是一個光線漏鬥！
This refraction has a couple of interesting results.
這種折射可以導致幾個有趣的結果。
For one thing, the light from the top of a distant object is bent down, and the light from the bottom is bent up.
首先，來自遠處物體頂部的光是向下彎折的，而來自底部的光是向上彎折的。
When this light comes to a focus, it means you see the object upside-down!
當光線聚焦時，也意味著你會看到一個顛倒的物體！
It also flips left and right, which can be a little disconcerting, and takes getting used to when you're using a refracting telescope.
它也是左右顛倒的，這可能會讓人感到不適，所以當使用折射望遠鏡時，你需要花一點時間適應。
For another thing, the lens can magnify the image.
另一方面，透鏡可以放大圖像。
That's again because the light is bent, and the image created of object observed can appear larger than the object does by eye.
這同樣是因為光線彎折，物體透過透鏡所呈現的影像可以比肉眼看到的物體更大。
It depends on a lot of factors including the shape of the lens, the distance to the object, and how far away the lens is, but in the end what you get is an image that looks bigger.
它取決於很多因素，包括透鏡的形狀，到物體的距離，到透鏡的距離，無論如何，總之最後你會得到一個看起來更大的圖像。
That has obvious advantages: a planet like Jupiter is too far away to see as anything other than a dot to the eye, but a telescope makes it appear bigger, and details can then be seen.
這有顯而易見的好處：像木星這樣的行星離我們太遠了，用肉眼觀察只能看到一個小點，但通過望遠鏡觀察，細節就清晰可見了。
When Galileo and other early astronomers pointed their telescopes at the sky, multitudes were revealed: Craters on the Moon, the phases of Venus, Jupiter's moons, the rings of Saturn, and so much more.
當伽利略和其他早期天文學家把望遠鏡對準天空時，發現了許多東西：月球上的環形山、金星的相位、木星的衛星、土星的光環等等。
The Universe itself came into focus.
宇宙本身被放在了焦點之上。
When astronomers talk about using a telescope to make details more clear, they use a term called resolution.
當天文學家談到使用望遠鏡使細節更清楚時，他們會使用一個術語，叫做解析率。
This is the ability to separate two objects that are very close together.
這是區分兩個相距很近的物體的能力。
You're familiar with this; when you're driving on a road at night a distant car coming toward you appears as a single light.
其實你對這個很熟悉；當你在夜間駕車行駛時，遠處駛來的汽車開始只是一個光點。
When it gets closer, the light separates out — resolves — into two headlights.
當它越來越接近時，這個光點就分成了——即解析成了——兩盞前車燈。
A telescope increases resolution, making it easier to, say, split two stars that are close together, or to see details on the Moon's surface.
望遠鏡可以提高解析率，使兩顆相距較近的星星能更容易被分辨出來，或使月球表面的細節更容易被看到。
The resolution depends in part on the size of the objective; in general the bigger the telescope objective, the better your resolution is.
解析度部分取決於接物鏡的大小；一般來說，望遠鏡的物鏡越大，解析率就越高。
Resolution is more useful than magnification when talking telescopes.
解析度比放大能力對望遠鏡來說更有用。
Fundamentally, there is a limit to how well your telescope resolves two objects, but there's no limit to how much you can magnify the image.
從根本上說，你的望遠鏡解析兩個物體的能力是有限的，但放大圖像的能力是無限的。
If you magnify the image beyond what the telescope can actually resolve, you just get mush.
如果你把圖像放大到超出望遠鏡所能解析的範圍，你就只會得到一片模糊。
Refracting telescopes are great, but they suffer from a big problem: big lenses are hard to make.
折射望遠鏡很棒，但有一個致命缺陷：大型透鏡很難製造。
They get thin near the edge, and break easily.
透鏡邊緣越來越薄，因此很容易損壞。
Also, different colors of light bend by different amounts as they pass through the lens, so you might focus a red star, say, and a blue one will still look fuzzy.
此外，不同顏色的光通過鏡頭時彎折的程度也不同，所以當你使一顆紅色星星聚焦清晰時，一顆藍色的星星卻可能仍然很模糊。
No less a mind than Isaac Newton figured a way around this: Use mirrors.
只有艾薩克·牛頓這樣聰明的腦袋才能找出避免這個問題的方法：使用單面鏡。
Mirrors also change the direction light travels, and if you used a curved mirror you can also bring light rays to a focus.
單面鏡也可以改變光的傳播方向，如果你使用曲面鏡，你還可以讓光線匯聚到一個焦點。
Telescopes that use mirrors are called reflectors.
使用單面鏡的望遠鏡被稱為反射望遠鏡。
The advantages of reflectors are huge: you only have to polish one side of a mirror, where a lens has two sides.
反射鏡望遠鏡的優勢是巨大的：你只需要打磨鏡子的一面就行了，而透鏡需要打磨兩面。
Also a mirror can be supported along its back, so they can be manufactured much larger more easily and for less money.
此外，單面鏡可以從背面被支撐，所以花更少的錢就可以更輕鬆地製造出更大單面鏡。
Although there have been many improvements made over the centuries, most big modern telescopes at their heart are based on the Newtonian design, and in fact no large professional-grade telescopes made today have a lens as their objective.
儘管幾個世紀以來已經有了很多改進，但大多數大型現代望遠鏡的核心都是基於牛頓的設計，事實上，現在製造的大型專業級望遠鏡都不使用透鏡作為接物鏡。
Nowadays, it's all done with mirrors.
它們全部都採用的單面鏡。
And that brings us to this week's aptly named Focus On.
這就把我們引向了本周名副其實的「焦點問題」。
The most common question I'm asked (besides, "Hey, who does your hair?") is, "Hey, Phil, what kind of telescope should I buy?"
我最常被問到的問題是(除了「嘿，你的頭髮是誰做的?」之外)，「嘿，菲爾，我該買哪種望遠鏡呢？」
It's a legitimate question, but it's very difficult to answer.
這是個合理的問題，但卻很難回答。
Imagine someone walked up to you and asked, "What kind of car should I buy?"
就像有人朝你走過來，問：「我該買哪種車？」一樣。
That's impossible to answer without a lot more information.
如果沒有更多的信息，則幾乎不可能有答案。
Same for telescopes.
望遠鏡也是一樣。
Do you want to look at the Moon and planets, or fainter, more difficult to spot galaxies?
你是想看月球和行星，還是想看更暗、更難以發現的星系？
Are you really devoted to this, or is it more of a pastime?
你真的對此全身心投入嗎？還是僅用來消磨閒暇時光？
Is this for a child or an adult?
是小孩用還是大人用？
These questions are critical.
這些問題都很重要。
Most small 'scopes are refractors, which are good for looking at detail on the Moon and planets (they tend to magnify the image more than reflectors do).
大多數小型望遠鏡都是折射鏡，它們對於觀察月亮和行星來講不錯(它們比反射鏡更利於放大圖像)。
But they're tricky to use because they flip the image left and right and up and down.
但是它們使用起來很複雜，因為它們會把圖像上下左右顛倒。
Bigger scopes are good for fainter objects, but are more expensive, and can be difficult to set up and use.
更大的鏡筒對觀測更暗的物體比較有利，不過它們也更貴，而且更難安裝與使用。
I hate hearing about a scope that just collects dust because it was bought in haste.
我不喜歡聽到有人說由於購買太倉促，他們的望遠鏡只能用來積灰這樣的話。
So here's what I recommend: find an observatory, planetarium, or local astronomy club.
所以我的建議是：去找一個天文臺、天文館，或者當地的天文俱樂部。
They're likely to have star parties, public observing events, where you can look at and through different kinds of telescopes.
他們通常會舉辦觀星聚會、公開觀測活動，在這些活動中你可以通過不同種類的望遠鏡進行觀測。
Their owners are almost universally thrilled to talk about them - as an astronomer, I can assure that the problem with astronomers isn't getting them to talk, it's shutting them up - so you'll get lots of great first-hand advice and experience.
他們的擁有者多半非常樂意談論它們——作為一名天文學家，我估計最難的問題不是讓天文學家打開話匣子，而是讓他們閉嘴——所以你會得到很多很棒的第一手建議和經驗。
Also, I usually recommend getting binoculars before a telescope.
另外，我通常建議在買天文望遠鏡之前先買個雙筒望遠鏡。
They're easy to use, fun to use, easy to carry around, and you can get good ones for less money and still see some nice things.
它們使用起來更方便，也更有趣，還便於攜帶，並且你只需花更少的錢就能買到相當不錯的雙筒望遠鏡，還能看到一些不錯的東西。
Even if you decide not to get more into astronomy as a hobby, they can also be used during the day on hikes and for bird watching.
即使你最終決定不再向天文這個愛好投入更多，你也仍然可以在徒步旅行或觀鳥時用上雙筒望遠鏡。
I have a couple of pair of binoculars and I use them all the time.
我就有幾副雙筒望遠鏡，我經常使用它們。
There's a third aspect to telescopes that's very important, beyond resolution and making faint things easier to see.
對於天文望遠鏡，除了解析度和讓暗淡的物體更容易被看到外，還有第三個非常重要的方面。
They can literally show us objects outside of the range of colors our eyes can see.
它們可以向我們展示肉眼所能看到的顏色範圍之外的物體。
In the year 1800, William Herschel discovered infrared light, a kind of light invisible to our eyes.
1800年，威廉·赫歇爾發現了紅外線，這是一種肉眼看不見的光。
In the time since we've learned of other forms of invisible light: radio, microwave, ultraviolet, X-rays, and gamma rays.
隨著時間推進，我們學到了很多其他類型的不可見光：無線電、微波、紫外線、X射線和伽瑪射線。
Astronomical objects can be observed in all these flavors of light, if we have telescopes that are designed to detect these flavors of light.
如果我們有專門為探測這些光線設計的望遠鏡，我們就能觀察到各種不同的天體。
Radio waves pass right around "normal" telescopes, ones that we use to observe visible light.
無線電波會從我們用來觀測可見光的「普通」望遠鏡周邊穿過。
X-rays and gamma rays pass right through them as if they aren't even there.
X射線和伽馬射線會直接穿過它們，就好像它們根本不存在一樣。
But we're smart, we humans.
但我們人類很聰明。
We learned that giant metal dishes can and will bend radio waves, and can be formed just like gigantic Newtonian mirrored telescopes.
我們了解到巨型金屬碟可以彎折無線電波，並且可以像巨型牛頓式反射望遠鏡那樣被建造。
In fact, different forms of light need different kinds of telescopes, and once we figured out how, we've built them.
事實上，不同類型的光需要不同種類的望遠鏡，一旦我們找到了方法，我們就會建造它們。
We can now detect cosmic phenomena across the entire spectrum of light, from radio waves to gamma rays, and have even built unconventional telescopes that detect subatomic particles from space as well, such as neutrinos and cosmic rays.
我們現在可以探測整個光譜範圍內的宇宙現象，從無線電波到伽馬射線，甚至還建造了非常規的望遠鏡來探測太空中的亞原子粒子，比如中微子和宇宙射線。
Because of this, we have learned far more about the Universe than Galileo could have imagined.
正因為如此，我們對宇宙的了解遠遠超出了伽利略的想像。
And we're in the midst of another revolution, too.
而且我們也正處於另一場革命之中。
The actual biophysics is complicated, but in a sense our eyes act like movie cameras, taking pictures at a frame rate of about 14 images per second.
我們眼睛的生物物理非常複雜，但在某種程度上來講，我們的眼睛就像電影攝像機一樣，以大約每秒14幀的速度不斷拍照。
That's a short amount of time.
這是非常短的時間。
Photographs, though, can take far longer exposures, allowing the light to build up, allowing us to see much fainter objects.
然而，照相機卻能曝光更長的時間，允許光線不斷累積，我們就能看到更模糊暗淡的物體。
The first photographs taken through a telescope were done in the 1800s.
第一張通過望遠鏡拍攝的照片攝於1800年代。
This has led to innumerable discoveries; for example, in the 20th century giant telescopes with giant cameras revealed details in distant galaxies that led to our understanding that the Universe is expanding, a critically important concept that we'll dive into later in the series.
這導致了一系列的新發現；例如，在20世紀，載有大型攝像機的巨型望遠鏡揭示了遙遠星系的很多細節，這使我們了解到宇宙正在膨脹，這是一個極其重要的概念，我們將在本系列的後面深入探討。
And now we have digital detectors, similar to the ones in your phone camera, but far larger and far more sensitive.
現在我們有了數字探測器，它們和手機攝像頭類似，但是更大更靈敏。
They can be dozens of times more light-sensitive than film, able to detect in minutes objects that would've taken hours or more to see using film.
它們對光線的敏感度是膠片的幾十倍，能夠在幾分鐘內探測到需要幾個小時甚至更長時間才能看到的物體。
These digital cameras can also be designed to detect ultraviolet light, infrared, and more.
數位相機還可以用來探測紫外線、紅外線等。
We can store vast amounts of that data easily on computers, and use those computers to analyze that huge ocean of information, performing tasks too tedious for humans.
我們可以很容易地在計算機上存儲大量的數據，並使用這些計算機來分析這浩瀚的信息海洋，執行對人類來說過於繁瑣的任務。
Most asteroids and comets are discovered using autonomous software, for example, looking for moving objects among the tens or hundreds of thousands of fixed stars in digital images.
大多數的小行星和彗星都是通過自動化軟體發現的，例如，數碼照片中尋找成千上萬顆恆星中移動的物體。
This has also ushered in the era of remote astronomy; a telescope can be on a distant mountain and programmed to scan the sky automatically.
於是人們也迎來了遠程天文時代；一臺望遠鏡可以位於遙遠的山頂，並被程序設定為自動掃描天空。
It also means we can loft telescopes into space, above the sea of air in our atmosphere that blurs and distorts distant, faint objects.
這也意味著我們可以將望遠鏡架設到太空中，處於會使遙遠或暗淡的物體更模糊的大氣層之上。
We can visit other worlds and send the pictures and data back home, or put observatories like the Hubble Space Telescope into orbit around the Earth and have it peer into the vast depths of the Universe.
我們可以訪問其他的世界，並把圖片和數據傳送回地球，或者把像哈勃太空望遠鏡這樣的觀察站送入繞地軌道，讓它向宇宙縱深處窺探。
I would argue that the past century has seen a revolution in astronomy every bit as important as the invention of the telescope in the first place.
我想說，在最近的這一個世紀中天文學家的變革與當初望遠鏡的發明一樣重要。
In the early 17th century the entire sky was new, and everywhere you pointed a telescope there was some treasure to behold.
早在17世紀，整片天空對人來說都是嶄新的，把望遠鏡指向任何地方都能看到一些等待被發現的寶藏。
But with our huge telescopes and incredibly sensitive digital eyes now, that's still true.
雖然現在我們有了巨型望遠鏡和極度敏感的數碼觀測眼，這仍然正確。
We learn more about the Universe every day, just as we learn that there's more to learn every day, too.
我們每天會了解到更多關於宇宙的知識，就像我們意識到每天都有更多的知識要去學習一樣。
That's one of the best parts of being an astronomer; the Universe is like a jigsaw puzzle with an infinite number of pieces.
這是當個天文學家最棒的事情之一；宇宙就像一塊有無限碎片的拼圖。
The fun never ends.
你從中獲得的樂趣永遠不會結束。
And remember: even with all the wonders revealed by telescopes, your eyes are still pretty good instruments, too.
記住：雖然望遠鏡能展示更多奇妙的景象，你的雙眼也仍然是很好的觀測工具。
You don't need big fancy equipment to see the sky.
你並不需要高端的儀器來觀察天空。
The important thing is to go outside.
重要的是走出門。
Look up!
抬頭看！
That's fun too.
這也充滿樂趣。
Today you learned that telescopes do two things: increase our ability to resolve details, and collect light so we can see fainter objects.
今天你學到瞭望遠鏡可以做兩件事：提高我們分辨物體細節的能力，以及收集光線以便我們能看到更暗淡的物體。
There are two main flavors of telescope: refractors, which use a lens, and reflectors, which use a mirror.
望遠鏡有兩種類型：使用透鏡的折射鏡和使用單面鏡的反射鏡。
There are also telescopes that are used to look at light our eyes can't see, and with the invention of film, and later electronic detectors, we have been able to probe the Universe to amazing depths.
還有一些望遠鏡是用來觀察我們肉眼看不到的光的，另外隨著膠片以及後來的電子探測器的發明，我們對宇宙的探測已經可以達到驚人的深度了。
Crash Course is produced in association with PBS Digital Studios.
Crash Course 是與 PBS 數字工作室聯合製作的。
This episode was written by me, Phil Plait.
我是菲爾·普萊特，這一集是由我創作的。
The script was edited by Blake de Pastino, and our consultant is Dr. Michelle Thaller.
腳本由 Blake de Pastino 編輯，我們的顧問是 Michelle Thaller 博士。
It was co-directed by Nicholas Jenkins and Michael Aranda, and the graphics team is Thought Café.
本片由尼古拉斯·詹金斯(Nicholas Jenkins)和麥可·阿蘭達(Michael Aranda)聯合執導，視頻畫麵團隊是 Thought Cafe。