# 費曼誕辰：談科學精神、機率和不確定性

It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.

We have found it of paramount importance that in order to progress we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty – some most unsure, some nearly sure, but none absolutely certain.

There’s a kind of saying that you don’t understand its meaning, ‘I don’t believe it. It’s too crazy. I’m not going to accept it.’… You’ll have to accept it. It’s the way nature works. If you want to know how nature works, we looked at it, carefully. Looking at it, that’s the way it looks. You don’t like it? Go somewhere else, to another universe where the rules are simpler, philosophically more pleasing, more psychologically easy. I can’t help it, okay? If I’m going to tell you honestly what the world looks like to the human beings who have struggled as hard as they can to understand it, I can only tell you what it looks like.

For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.

「如果要我誠實的告訴你，在盡力掙扎理解的人們眼中世界是如何運作的，我只能告訴你：它就是如此。」若我們都能銘記費曼這句說話，可能就是對他來說最好的生日禮物。

# 知道和理解的分別

What I cannot create, I do not understand.

Know how to solve every problem that has been solved.

# 你也能懂量子力學

I think I can safely say that nobody understands quantum mechanics.

1. 觀察之前，如果電子的自旋量子態是「向上」和「向下」的話，那麼在觀察之後，我們會發現有 50% 機會向上、 50% 向下；
2. 觀察之前，如果電子的自旋量子態是「(向上 + 向下) 除以開方 2」和「(向上 – 向下) 除以開方 2」的話，那麼在觀察之後，我們會發現有 50% 機會向上、 50% 向下。

WTF，這不是跟沒有說過話沒有分別嗎？？？我們會問，既然做這個實驗不能分辨到底是 case 1. 還是 case 2.，根據科學精神，我們應該選擇比較簡單的那個，即是 case 1. 吧！

[上圖由 b > c > d > e 是向著雙狹縫發射越來越來電子的結果，可以清晰的看到干涉現象。更奇異的是，實驗中每次只發射一個電子，所以就證明了電子會同時穿過兩個狹縫，然後自己和自己進行干涉。圖片來源：en.wikipedia.org/wiki/Double-slit_experiment]

# 好奇心和誠實：理查．費曼 (Richard P. Feynman)

“You know, the most amazing thing happened to me tonight… I saw a car with the license plate ARW 357. Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!”

“The beauty that is there for you is also available for me, too. But I see a deeper beauty that isn’t so readily available to others. I can see the complicated interactions of the flower. The color of the flower is red. Does the fact that the plant has color mean that it evolved to attract insects? This adds a further question. Can insects see color? Do they have an aesthetic sense? And so on. I don’t see how studying a flower ever detracts from its beauty. It only adds. I don’t understand how it subtracts.”

[加州理工學院現已把所有《費曼物理學講義》免費放在網上，任何人也可以讀到費曼教的物理學：http://www.feynmanlectures.caltech.edu]

“For a successful technology, reality must take precedence over public relation, for Nature cannot be fooled.”

(費曼的報告公開於 NASA 的網頁，所有人也可以看到：http://history.nasa.gov/rogersrep/v2appf.htm)

“I can live with doubt, and uncertainty, and not knowing. I think it is much more interesting to live not knowing than have answers which might be wrong.”

“I’d hate to die twice. It’s so boring.”

《別鬧了！費曼先生》(Surely You’re Joking, Mr. Feynman!)

《你管別人怎麼想》(What Do You Care What Other People Think?)

《費曼物理學講義》(The Feynman Lectures on Physics)

《費曼手札：不休止的鼓聲》(舊書名)／《出人意表，情理之中：費曼書信集》(新書名) (Perfectly Reasonable Deviation from the Beaten Track: The Letters of Richard P. Feynman)

《這個不科學的年代》(The Meaning of It All: Thoughts of a Citizen Scientist)

《費曼的彩虹》(Feynman’s Rainbow: A Search for Beauty in Physics and in Life)

《QED：光和物質的奇異性》(QED: The Strange Theory of Light and Matter)

Tuva or Bust! (費曼的最後歷險故事)

Quantum Man: Richard Feynman’s Life in Science