Did you know that your blood vessels taken together add up to 100,000 kilometers, enough to wrap them around the planet twice?

您知道嗎，您的血管加起來長達 10 萬公里，足以繞地球兩圈。

One of our favorite fun facts used in our book and app and a video and... wait, 100,000 kilometers is like... like a lot.

我們最喜歡的趣事之一，在我們的圖書、應用程序和視頻中都有使用......等等，10 萬公里好像......好像很多。

We've used it so often, but where did we get this number from?

我們經常使用它，但這個號碼是從哪裡來的呢？

And how do we know it's true?

我們怎麼知道這是真的？

Welcome to an epic research riddle that took us well over a year to figure out and led us on a strange and baffling journey.

歡迎來到一個史詩般的研究謎題，我們花了一年多的時間才弄明白這個謎題，它帶領我們踏上了一段奇特而又令人費解的旅程。

It began extremely innocently.

事情的起因非常單純。

We always collect interesting and fun facts to make our stories more colorful.

我們總是收集有趣好玩的事實，讓我們的故事更加豐富多彩。

And this one was just perfect.

而這一次簡直太完美了。

All of your blood vessels twice around the world.

你所有的血管都要繞地球兩圈。

Small thing, big number.

小事情，大數字。

Wow.

哇

But one day, someone asked where this number was actually from.

但有一天，有人問這個號碼究竟來自哪裡。

Did it really matter though?

但這真的重要嗎？

Because it had to be true.

因為這一定是真的。

If you Google variations of how long are your blood vessels put together, you'll find the same numbers over and over 100,000 kilometers or 60,000 miles.

如果你在谷歌上搜索 "你的血管有多長"，你會發現同樣的數字在十萬公里或六萬英里以上。

You find it in books, blogs, webpages of educational institutions, or lecture notes, reviews, scientific papers and articles.

你可以在書籍、博客、教育機構的網頁或講義、評論、科學論文和文章中找到這些資訊。

We ourselves have used it multiple times.

我們自己也多次使用過。

So it couldn't be that hard to find the source, right?

所以找到源頭並不難，對嗎？

Right?

對不對？

The first perplexing thing we noticed was that not a single one of the many, many websites, books or articles quoted the original source.

我們注意到的第一件令人困惑的事情是，在許許多多的網站、書籍或文章中，沒有一篇引用了原始出處。

Most didn't give a source at all.

大多數人根本沒有提供消息來源。

Some linked to each other.

有些是相互關聯的。

It seemed like the number was just accepted as a truism.

這個數字似乎已成為不爭的事實。

Very weird.

非常奇怪。

Even worse and more suspicious was that the number was used inconsistently.

更糟糕、更可疑的是，這個號碼的使用前後不一致。

Some said it's the total length of capillaries.

有人說是毛細血管的總長度。

Some said it's just veins plus arteries and others cited it as the length of everything put together.

有人說這只是靜脈加上動脈的長度，還有人說這是所有東西加在一起的長度。

Hmm.

嗯

Something wasn't right.

不對勁

We couldn't let this go.

我們不能就這樣算了。

Getting our facts straight is critical for what we do here.

弄清事實對我們的工作至關重要。

And since we've used this fact ourselves a few times, this now felt personal.

由於我們自己也曾多次使用過這一事實，所以現在覺得這很私人。

We needed to find the original source and solve this research riddle.

我們需要找到原始出處，解開這個研究之謎。

There had to be an original source.

必須有一個原始來源。

Random Googling just turned up thousands of sites that quoted the number, no lead to the original.

在谷歌上隨便搜索一下，就能找到成千上萬個引用這個數字的網站，但卻找不到原文。

So we moved on to PubMed, a search engine for biomedical science papers.

於是，我們轉向 PubMed，這是一個生物醫學科學論文搜索引擎。

Zero results.

結果為零。

Okay, weird.

好吧，奇怪。

Maybe if we tried a few different keyword combinations.

也許我們可以嘗試一些不同的關鍵詞組合。

Nothing.

什麼都沒有

Hmm.

嗯

Hmm.

嗯

Okay, finally, we found a bunch of scientific papers, but still, not a single one referenced the original source.

好吧，我們終於找到了一堆科學論文，但仍然沒有一篇引用原始出處。

The number also showed up in two different biology textbooks.

這個數字還出現在兩本不同的生物教科書中。

We contacted the authors, but they told us the number has been circulating for decades and that they'd also be curious to know where it comes from.

我們聯繫了作者，但他們告訴我們，這個數字已經流傳了幾十年，他們也很想知道這個數字的來源。

Maybe we needed to go back to the olden days.

也許我們需要回到過去。

So we narrowed our search to the last few decades, starting with the 1990s.

是以，我們將搜索範圍縮小到最近幾十年，從 20 世紀 90 年代開始。

And would you look at that?

你能看看嗎？

We found two books, Vital Circuits by Steven Vogel and Looking at the Body by David Suzuki.

我們找到了兩本書：史蒂文-沃格爾（Steven Vogel）的《生命電路》（Vital Circuits）和大衛-鈴木（David Suzuki）的《觀察身體》（Looking at the Body）。

And it turned out Dr. Suzuki is an OG science communicator with a PhD in zoology, who started doing popular programming in the 1970s on Canadian television.

原來，鈴木博士是一位擁有動物學博士學位的老牌科學傳播者，上世紀70年代開始在加拿大電視臺做科普節目。

He has 29 honorary degrees and has written 52 books.

他擁有 29 個榮譽學位，撰寫了 52 本著作。

Impressive.

令人印象深刻。

He may either be the original source, or at least know what it is.

他可能是原始資訊來源，或者至少知道是什麼。

So we ordered Looking at the Body to look for it.

於是，我們訂購了《屍體觀察》來尋找它。

And here it is.

就在這裡。

If all the body's blood vessels were laid end to end, they would stretch 96,000 kilometers, 60,000 miles.

如果將人體的所有血管從頭鋪到尾，它們將綿延 9.6 萬公里，即 6 萬英里。

That's about two and a half times around the world.

這相當於繞地球兩圈半。

But again, no source.

但同樣沒有消息來源。

It turned out he's still around doing things in his late eighties.

原來，他年近八旬還在做著一些事情。

So we thought maybe if we asked Dr. Suzuki personally, he might know where the numbers from.

所以我們想，如果我們親自去問鈴木博士，他也許會知道這些數字是怎麼來的。

He had no public email, but a personal inquiry is possible by writing a letter to Dr. Suzuki.

他沒有公開的電子郵件，但可以寫信給鈴木博士進行個人查詢。

Very old school, very respectable.

非常老派，非常值得尊敬。

So we wrote a letter.

於是我們寫了一封信。

Dear Dr. Suzuki, we're writing to you on a matter of grave importance.

親愛的鈴木博士，我們給您寫信是為了一件非常重要的事情。

What is the original source for the 100,000 kilometers?

10 萬公里的原始出處是什麼？

Our internet video and our sanity depend on it.

我們的網絡視頻和理智都取決於此。

Pretty please.

拜託了

Respectfully yours, Kurzgesagt fact checkers.

Kurzgesagt 事實核查人員謹此致敬。

Three weeks later, we actually got a reply.

三週後，我們真的收到了回覆。

Dear weird internet people.

親愛的網絡怪人

Unfortunately, Dr. Suzuki does not recall the source of this available to look it up.

遺憾的是，鈴木博士不記得這一資訊的來源，無法查找。

Good luck with your project.

祝你的項目好運。

You're going to need it.

你會需要它的。

Kind regards, public information coordinator.

謹致問候，公共信息協調員。

Okay.

好的

They didn't quite use these words and were actually really nice, but still bummer.

他們並沒有說這些話，實際上態度很好，但還是很掃興。

Maybe the 1992 popular science book by Steven Vogel, a Duke University biomechanics professor would be more helpful.

杜克大學生物力學教授史蒂文-沃格爾（Steven Vogel）1992 年出版的科普讀物或許更有幫助。

It has this sentence, combined length of pipes, 100,000 kilometers, 60,000 miles, more than twice around the earth at the equator.

它有這樣一句話：管道的總長度為 10 萬公里，即 6 萬英里，在赤道上繞地球兩圈多。

So the book talks about this on one of its 300 pages, but where is the source?

那麼，這本書在其 300 頁中的一頁談到了這一點，但來源在哪裡呢？

Unfortunately, there's only a list of 93 references and sources with no indication where in the book they're pointing to.

遺憾的是，書中只有一份 93 條參考文獻和資料來源的清單，卻沒有說明這些參考文獻和資料來源在書中的什麼位置。

Our original source may be in one of the papers, books, and articles in this list.

我們的原始資料可能來自本列表中的論文、書籍和文章。

Ouch.

哎喲

Reading all of those would take weeks.

讀完所有這些需要幾周時間。

Was this really or had we got lost in the forest of human knowledge, looking for answers to questions nobody's asking and nobody cares about, but we'd wasted so much time already.

這究竟是真的，還是我們在人類知識的森林中迷失了方向，在尋找無人問津、無人關心的問題的答案，但我們已經浪費了太多的時間。

So we decided to just do that one by one.

所以我們決定一個一個來。

And now for a change, we just got stupidly lucky for no particular reason.

現在，我們換了一種方式，我們只是愚蠢地走運了，沒有什麼特別的原因。

We decided to check the sources from last to first.

我們決定檢查從最後到最先的資訊來源。

And it turned out the very source we checked first was what we were looking for.

結果發現，我們首先查看的資訊來源正是我們要找的。

A scientific American article from 1959, the micro circulation of the blood.

1959 年的一篇美國科普文章《血液的微循環》。

So we got a scan of this 65 year old science magazine, and there it was.

於是，我們拿到了這本 65 年前的科學雜誌的掃描件，它就在那裡。

But this was still not the original source.

但這仍然不是原始來源。

But it did reference where it got the number from.

但它確實提到了數字的來源。

The anatomy and physiology of capillaries, a 1922 book by August Kroll, winner of a Nobel Prize for medicine.

毛細血管的解剖學和生理學》，1922 年諾貝爾醫學獎得主奧古斯特-克羅爾的著作。

He probably knew what he was talking about.

他可能知道自己在說什麼。

So we ordered his book and bingo, we got the original source.

於是，我們訂購了他的書，結果我們得到了原始資料。

The book is a collection of Kroll's lectures and was highly praised by experts at the time.

該書是克羅爾的演講集，受到當時專家的高度讚揚。

It summarizes his research and adds new experiments, ideas, and hypotheses.

它總結了他的研究，並增加了新的實驗、想法和假設。

So here it was, the original source, used thousands of times for over a century.

這就是它，一個多世紀以來被使用了數千次的原始資料。

Supposing a man's muscles to weigh 50 kilograms, and his capillaries to number 2000 per square millimeter, the total length of all these tubes put together must be something like 100,000 kilometers, or two and a half times around the globe and their total surface 6300 square meters.

假設一個人的肌肉重 50 千克，毛細血管每平方毫米有 2000 根，那麼所有這些管道的總長度加起來肯定有 10 萬千米，或者說繞地球兩圈半，總面積為 6300 平方米。

While other scientists had speculated on the length of all the capillaries before, Kroll was the first to make a real estimate based on experiments.

雖然其他科學家也曾推測過所有毛細血管的長度，但克羅爾是第一個根據實驗做出真實估計的人。

Something very solid.

非常堅實的東西。

Okay, and now that we were here, was it correct?

好吧，既然我們已經到了，那這是正確的嗎？

Kroll's book includes this rather cryptic table without calculations or explanations.

克羅爾的書中有一張相當隱晦的表格，沒有計算也沒有解釋。

It seems to have been obvious to him, but not to us looking at it a century later.

這對他來說似乎是顯而易見的，但對一個世紀後的我們來說卻並非如此。

We needed to actually read the book.

我們需要真正讀一讀這本書。

In a very breakthrough science-y kind of way, Kroll just winged it.

從科學突破的角度來看，克羅爾只是 "插翅難飛"。

In a nutshell, he cut muscle samples from different animals, started counting, and made some rule-of-thumb assumptions.

簡而言之，他從不同的動物身上切下肌肉樣本，開始計數，並根據經驗做出一些假設。

Today, we know that his assumptions about the density of capillaries in humans was quite off.

今天，我們知道他對人體毛細血管密度的假設有很大偏差。

On top of that, he used a kind of idealized bodybuilder human weighing 143 kilograms with 50 kilograms of pure muscle mass.

此外，他還使用了一種理想化的健美運動員，體重 143 千克，純肌肉量 50 千克。

And this finally gave him the very pleasing number of 100,000 kilometers.

最終，他獲得了 10 萬公里這個令人欣喜的數字。

It would be unfair to blame Kroll.

指責克羅爾是不公平的。

This was just a small ancillary fact he probably calculated for elemental to his body of work.

這只是他可能計算出的他的作品中的一個小小的附帶事實。

But he was a world expert, so his incorrect number was used in scientific papers, spread, and became dogma, eventually entirely detached from the original source.

但他是一位世界級專家，是以他的錯誤數字被用於科學論文中，並傳播開來，成為教條，最終完全脫離了原始來源。

At this point in our research, over a year had passed.

此時，我們的研究已經過去了一年多。

So just to be sure, we did another Google search and, while we were caught up in our personal mission to find the source, up to the neck in old books, writing letters to Canada, scientists quietly published a paper, not really getting a lot of attention from anybody.

為了確保萬無一失，我們又在谷歌上搜索了一下，當我們沉浸在尋找源頭的個人使命中，埋頭於舊書，給加拿大寫信時，科學家們悄悄地發表了一篇論文，並沒有引起任何人的注意。

They calculated a new number, a way more accurate estimate.

他們計算出了一個新的數字，一個更準確的估計數字。

If we had just waited another year, we could have saved doing all that work.

如果我們再多等一年，就可以省去這些工作了。

Hmm.

嗯

So, now, here it is.

所以，現在，它就在這裡。

According to the newest science, the length of all the capillaries in a human is somewhere between 9,000 and 19,000 kilometers.

根據最新的科學研究，人類所有毛細血管的長度大約在 9 000 到 19 000 公里之間。

Very impressive, but not enough to go the world.

非常了不起，但還不足以走向世界。

A sort of conclusion.

一種結論。

If you look up the question today, you'll likely still not find the real answer, but thousands of sources, among them one Kurzgesagt video, using the wrong number, and it will probably stay like that for a while.

如果你今天查找這個問題，你很可能仍然找不到真正的答案，但成千上萬的資訊來源，其中包括一個 Kurzgesagt 視頻，都使用了錯誤的數字，而且可能會保持一段時間。

In all this time, why did nobody bother to double check this?

這麼長時間以來，為什麼沒有人去仔細檢查一下呢？

Well, because the reality is it's extremely hard and time-consuming.

嗯，因為現實情況是，這非常困難而且耗時。

As we mentioned before, it took us a year and a great deal of luck to get to the bottom of this on our own.

正如我們之前提到的，我們花了一年的時間，靠自己的運氣才弄清了真相。

Investing this time and effort while you're writing a paper is just not feasible for most scientists or science communicators.

對於大多數科學家或科學傳播者來說，在撰寫論文時投入這樣的時間和精力是不可行的。

If a number seems safe and is used by credible sources, most people, including us, end up quoting a secondary source or worse.

如果一個數字看起來很安全，而且被可靠的來源使用，那麼包括我們在內的大多數人最終都會引用第二手資料，甚至更糟。

Also, it's just such a nice round number that will stick with you once you've heard it.

此外，這個圓圓的數字也很好聽，聽過之後會讓人記憶猶新。

Facts that seem beautiful tend to survive much longer.

看似美好的事實往往能存活得更久。

But that's exactly the problem, isn't it?

但這正是問題所在，不是嗎？

The most interesting stories survive on the internet, and often, with each retelling, they get more exciting and memorable.

最有趣的故事都會在互聯網上流傳，而且往往每複述一次，它們就會變得更加精彩、更加令人難忘。

It takes a lot of energy to get to the bottom of things, and a factoid is easily repeated, so misinformation can persist.

刨根問底需要耗費大量精力，而且一個事實很容易被重複，是以錯誤信息會持續存在。

When we started this research, we didn't think we'd end up here.

當我們開始這項研究時，我們沒想到會在這裡結束。

You, dear viewer, got a little peek into the kinds of mazes we have to navigate just to tell you our short science-y stories.

親愛的觀眾朋友們，為了給你們講述我們的科學小故事，我們不得不穿越重重迷宮。

They are as true as we can possibly make them.

它們是我們所能做到的最真實的東西。

We'll run into the same traps as everybody else from time to time.

我們時不時會遇到和其他人一樣的陷阱。

But we're doing our best to correct misinformation, give more context, and bring you the latest science on any topic we cover.

但我們會盡最大努力糾正錯誤資訊，提供更多的背景資料，併為您帶來我們所報道的任何話題的最新科學資訊。

See you next time.

下次再見

Challenging common wisdom and following the evidence can sometimes lead you to places you don't expect to end up.

挑戰常識和遵循證據有時會把你帶到意想不到的地方。

If you want to do more good in the world, approaching it like a scientist or a researcher could open up new ideas and career paths you didn't know existed.

如果你想在這個世界上做更多好事，像科學家或研究人員那樣去做，可能會開闢出你不知道的新思路和職業道路。

Today's sponsor 80,000 Hours can help you on this journey. 80,000 Hours is a non-profit career advice organization that wants to help people find fulfilling careers that also do a lot of good in the world.

今天的贊助商 80,000 小時可以在這條路上為您提供幫助。80,000 小時是一家非營利性職業諮詢機構，希望幫助人們找到充實的職業，同時也為世界做很多好事。

And their advice is free, without any hidden cost or fee later on.

而且他們的建議是免費的，沒有任何隱藏成本或後續費用。

Like us, they care a lot about making sure their work is based on the best available evidence and consultation with experts.

和我們一樣，他們也非常重視確保自己的工作以現有的最佳證據和專家諮詢為基礎。

So they've spent the last decade compiling and conducting research into topics like how much impact can one person actually have?

是以，他們花了十年時間對一些主題進行了彙編和研究，比如一個人究竟能產生多大的影響？

And what are the best ways to make a positive difference on important global issues?

在重要的全球性問題上發揮積極作用的最佳方式是什麼？

Turns out, following a well-known career path isn't your only option to achieve that goal.

事實證明，追隨一條眾所周知的職業道路並不是實現這一目標的唯一選擇。

In fact, there may be many paths that make an even bigger difference in the world that you may not have even heard of.

事實上，可能有很多道路會給世界帶來更大的變化，而這些道路你可能聞所未聞。

The time you'll spend on your career is probably your biggest opportunity to have an impact.

你在職業生涯中花費的時間可能是你產生影響的最大機會。

If you want to make the most of it, join the newsletter now and get a free copy of their in-depth career guide sent to your inbox.

如果您想充分利用它，現在就加入時事通訊，免費獲得一份發送到您收件箱的深度職業指南。

Just sign up at 80,000hours.org in a nutshell. support of our patrons they are a huge safety net for us and allow us to work on our videos until they're perfect if you also want to support us in our mission of creating factful and reliable content that makes you go whoa come join our patreon flock in return you'll receive perks like your own kotzgesagt burp exclusive behind-the-scenes insights into our work or sneak peeks of our next topics become a patron become a part of kotzgesagt and help us provide trustworthy science content on the internet

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