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Leonard Susskind 談我的朋友理查.費曼

Leonard Susskind: My friend Richard Feynman

 

Photo of three lions hunting on the Serengeti.

講者:Leonard Susskind

2011年1月演講,2011年5月在TEDxCaltech上線

 

翻譯:洪曉慧

編輯:朱學恆

簡繁轉換:洪曉慧

後製:洪曉慧

字幕影片後制:謝旻均

 

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關於這場演講

身為天才的好友會是什麼情形?在TEDx加州理工講台上,物理學家Leonard Susskind講述了幾個關於他與傳奇人物理查.費曼的友誼故事,討論他對嚴重及不嚴重問題的非傳統處理方法。

 

關於Leonard Susskind

Leonard Susskind於史丹佛大學研究弦理論、量子場論、量子統計力學和量子宇宙學。

 

為什麼要聽他演講

Leonard Susskind是史丹佛大學物理系的Felix Bloch講座教授。他的研究興趣包括弦理論、量子場論、量子統計力學和量子宇宙學。他於1975年獲得紐約科學院頒發的Pregel獎,於1998年獲得美國物理學會頒發的J. J. Sakurai Prize獎,「因為他對強子弦模型、格點規範場論、量子色動力學和動力學對稱破缺上的開創性貢獻。」他是美國國家科學院及美國藝術與科學院成員,自2009年以來,一直擔任史丹佛大學理論物理研究所所長。

 

他最近以《黑洞戰爭:我與史蒂芬霍金並肩作戰讓世界可以接受量子力學》一書獲頒洛杉磯時報科技類圖書獎。

 

Leonard Susskind的英語網上資料

Bio: Leonard Susskind at TEDxCaltech

 

[TED科技‧娛樂‧設計]

已有中譯字幕的TED影片目錄(繁體)(簡體)。請注意繁簡目錄是不一樣的。

 

Leonard Susskind 談我的朋友理查.費曼

當我被要求這麼做時,我決定我真正想談的是我的朋友理查.費曼。我是少數的幸運者之一,真正有機會瞭解他並享受他的存在,我將要告訴你們我所知的理查.費曼。我敢肯定現場還有其他人能告訴你們他所知的理查.費曼,或許是個不同的理查.費曼。

 

理查.費曼是個相當複雜的人,他是個才華洋溢的人,當然,最重要的,他是一個非常、非常、非常偉大的科學家。他是一個演員,你們看過他的演出,我也有幸身處那些演講現場,坐在看台上聆聽,每場都相當出色。他是一位哲學家,一位鼓手,他是一位卓越的老師。理查.費曼也是一個引人注目的人,超級引人注目,他性急、無禮,充滿男子氣概,是一種勝人一籌的男子氣概。他喜愛智力競爭,他擁有超級巨大的自我,但這個男人在他的底層上擁有寬廣的空間,我的意思是,這是很大的空間,以我的情況來說,我不知道該怎麼讓其他人明白,但對我來說,是給另一個大的自我廣大的空間。嗯,沒有他的那麼大,但相當大。我跟Dick在一起時感覺總是很好(Dick是費曼的小名)。

 

跟他在一起總是很有趣,他總是讓我覺得自己很聰明。一個像這樣的人怎麼可能讓你覺得自己很聰明?不知怎麼的,他辦到了。他讓我感覺我很聰明,他讓我感覺他很聰明,他讓我感覺我們兩個都很聰明,我們兩個可以解決任何問題。事實上,我們的確有時也一起研究物理,我們從未一起發表過一篇論文,但我們確實從中得到很多樂趣。他喜歡贏,以我們有時會玩的一些男人的小遊戲來說,他不只跟我玩而已,他跟各式各樣的人玩,他幾乎總是獲勝,但當他沒有贏,當他輸了時,他會大笑,似乎跟他贏了時擁有同樣多的樂趣。

 

我記得他曾經告訴我一個故事,關於學生們對他開的一個玩笑,他們帶他-我想這是為了他的生日,他們帶他去吃午餐,一個在Pasadena賣三明治的地方,那間店可能還在,我不知道。他們的特色是名人三明治,你可以點一客瑪麗蓮夢露三明治,或一客亨佛萊鮑嘉三明治。學生們提前去那裡,他們說好大家都點費曼三明治,一個接一個的,他們進去點了費曼三明治。費曼喜歡這個故事,他告訴我這個故事,他真的很快樂而且開懷大笑。當他說完這個故事,我對他說,「Dick,我想知道費曼三明治和Susskind三明治之間有什麼差別?」不加思索的,他說:「嗯,它們大致上相同,唯一的區別就是Susskind三明治的火腿比較多。」火腿就是指壞傢伙(笑聲)。嗯,我剛好那天反應很快,我說,「是啊,但少了很多大香腸(baloney,亦有鬼扯之意)。」

 

(笑聲)

 

但事實上,費曼三明治有很多火腿,但絕對沒有大香腸。費曼比任何事都討厭的就是矯飾的智慧,虛假、錯誤的詭辯、專業術語。我記得在80年代某個時候,80年代中期,Dick和我及Sidney Coleman巧遇了幾次,在舊金山某個非常有錢的人家裡,我們在舊金山吃晚餐,那個有錢人最後一次邀請我們時,他也邀了幾位哲學家,那些人是心靈哲學家,他們的專長是意識哲學,他們滿嘴各式各樣的專業術語,我試著記起那些字眼,「一元論」、「二元論」,四處充斥著這類話語,我不知道這些東西是什麼意思,Dick也不知道,Sydney也搞不清楚這些。

 

那我們談了什麼?嗯,當你們談論心智時會談到什麼?有一件事,很顯然會談到的一件事是,機器可以成為一個心智產物嗎?你能建造出一種像人類般思考,具有意識的機器嗎?我們坐在一起,談論到這一點-我們當然沒有解決這個問題,哲學家的問題在於,他們用哲學思考它們什麼時候應該會成為科學上的變異,這畢竟是一個科學問題,在Dick身邊這麼做是非常、非常危險的,費曼讓他們得到-一頓狠狠攻擊,讓他們大吃一驚,這很殘酷、很有趣-噢,這很有趣,但真的很殘酷,他真的讓他們很漏氣。

 

但令人驚奇的是,費曼必須提早一點離開,他不太舒服,所以得提早一點離開,Sidney跟我與兩個哲學家一起離開,令人驚奇的是,這些傢伙飄飄然的,他們太高興了,他們遇上這個偉人,他們受教於他,他們雖臉上無光,卻在其中享受到大量樂趣,這是很特別的事,我意識到費曼有某種非凡之處,即使在他做這些事的時候。

 

Dick是我的朋友,我一向叫他Dick,Dick和我確實有一點關係,我想我跟他之間的或許是一種特殊的關係,我們喜歡對方,我們喜歡同一種事物,我也喜歡那種男人的智力遊戲,有時我會獲勝,大多時候是他贏,但我們都喜歡這種遊戲,Dick越來越相信,在某個時刻,他和我有某種相似的個性,我不認為他是對的,我認為我們之間唯一相似的一點是,我們都喜歡談論自己,但他堅信這一點。他很好奇,這個男人好奇的令人難以置信,他想了解它是什麼、為什麼是。這跟以下這件趣事有關。

 

有一天我們正走著,當時是在法國,在La Zouche,1976年,我們處於人生巔峰,我們處於人生巔峰,費曼對我說,他說,「Leonardo」,他之所以叫我Leonardo,是因為我們在歐洲,他正在練習法語,他說,「Leonardo,你小時候跟母親比較親近還是父親?」我說:「嗯,我真正的英雄是我的父親,他是個工人,有五年級的教育程度,他是一位熟練的機械工,他教我如何使用工具,他教導我所有關於機械的東西,他還教我畢氏定理,但他不是稱它為三角形的斜邊,他稱它為最短距離。」費曼的眼睛突然大睜,就像燈泡一樣亮起來,然後他說,他和他父親之間基本上的關係也正是這樣,事實上,有某段時刻他一直堅信,成為一個好物理學家,跟你父親擁有過這樣的關係非常重要。我很抱歉在這裡發表性別歧視談話,但事實上情況就是這樣。

 

他說他絕對堅信這是必要的,是年輕物理學家成長過程中的必要部份,身為Dick的他當然想證實一下,他想出去做一個實驗,所以他這麼做了,他走了出去,做了一個實驗,他問所有他認為是好物理學家的朋友說,「你是受到母親或是父親的影響?」毫無例外的-所有在場的都是男性,毫無例外的,每一個人都說,「我的母親」(笑聲)。這讓這個理論沉入歷史的垃圾桶中,但他非常興奮,他畢竟曾遇見某個人,我跟父親之間的經歷就與他跟他父親一樣,有一段時間,他確信這就是我們相處得那麼好的原因。我不知道。也許吧。誰知道?

 

但讓我告訴你們一點關於費曼這個物理學家的事,費曼的風格-不,風格不是正確的形容詞,風格會讓你想到他可能戴過的領結或穿過的西裝,這是某種比那些更深刻的東西,但我想不出其他字眼來形容它。費曼的科學風格,總是尋找問題最簡單、最基本的可能解答,如果不可行,你就必須使用某些更具想像力的東西,但毫無疑問的部分是,向人們顯示他能想得比他們更簡單,是他最大的喜悅和快樂。但他也深信,他真的相信,如果你不能簡單解釋某種東西,你就不會瞭解它。1950年代,人們正試著瞭解超流體氦是如何作用的。

 

有一個來自俄羅斯數學物理學家的理論,這是一個複雜的理論,我會盡快告訴你們這是什麼理論,這是一個超級複雜的理論,充滿了非常困難的積分和公式和數學等等,它多少有點作用,但不是非常有用,它唯一可以運用的部份是,當氦原子相距非常非常遙遠時,氦原子間的距離必須非常遙遠,不幸的是,這是液態的氦原子,正好彼此緊靠。

 

費曼決定自己多少算是業餘氦物理學家,他將設法弄清楚,他有一個想法,一個非常清楚的想法,他將設法找出這個數量龐大的原子其量子波函數是什麼模樣,他試著想像,藉由為數不多的簡單法則引導,這為數不多的簡單法則非常非常簡單,第一個是當氦原子接觸時會彼此相斥,其中的含義是,這個波函數必定會趨近於零,當氦原子互相接觸時,它必定會消失。另一個事實是,在基態時,即量子系統的最低能量狀態,波函數總是非常平滑,有最低的波數。

 

於是,他坐了下來,我想像他只有用一張紙和一隻筆,他試著把它寫出來,也真的寫出來了,是你能想到的最簡單函數,其中有個邊界條件,即當粒子接觸時,這個波函數消失,其中間部份是平滑的,他寫下了一個簡單的式子,它是如此簡單,事實上,我懷疑一個真正聰明的高中生,甚至不用學過微積分,就能瞭解他寫下的東西,他寫下的東西就是這麼簡單,解釋了當時所知的一切關於液態氦的性質,還有一些其他的事。

 

我一直懷疑這些專家,真正的氦物理學專家對這一點是否有點不好意思,他們擁有超級強大的技術,卻無法同樣做到這一點。順帶一提,我將會告訴你們什麼是超級強大的技術,就是費曼圖這個技術。

 

(笑聲)

 

他於1968年再次做到了這個,1968年時,在我自己的大學中,我當時不在那裡,但1968年時他們正探索質子的結構,質子顯然是由一堆小粒子組成,大家多少知道這一點,而分析它的方法,當然,就是費曼圖,費曼圖就是為了這個而構建的,為了瞭解粒子實驗的進行過程,非常簡單,只需取一個質子,相當快速的用一個電子撞擊它,這就是費曼圖用來處理的事。唯一的問題是,費曼圖很複雜,難以積分,如果你能將它們全部解出,就會得到一個非常精確的理論,但你無法做到,它們太複雜了,人們試著做出它們,你可以做個一階圖,別擔心一階圖,一階、兩階-也許你可以做一個三階圖,但除此之外,你什麼都不能做。

 

費曼說,「忘了這一切,只要把質子想成是一群小粒子的集合,一群小粒子」,他稱它們為部分子,他說,「只要把它想成是一群移動得相當快的部分子。」因為它們真的移動得相當快,相對論說,其內部的移動變得非常緩慢,電子突然間撞擊,它就像是質子突然被快速撞擊,你們看到了什麼?你們看到了一群凍結的部分子,它們不會移動,因為它們不會移動,在實驗期間,你不須擔心它們如何移動,你不須擔心它們之間的作用力,你只需將它想成是一群凍結的部分子,這就是分析這些實驗的關鍵。非常有效,它確實-有人說革命不是一個好字眼,我想沒錯,所以我不會說這是革命,但這肯定讓我們對質子的瞭解有非常、非常深入的進展,對其他粒子來說也是。

 

嗯,我還要告訴你們更多一些,關於我和費曼之間的關係,他是什麼樣的人,但我看到只剩半分鐘時間,所以我想,就用以下內容做個結束。我實在不認為費曼會喜歡這場盛會,我想他會說「我不需要這個」。但我們應該如何向費曼致敬?我們應該怎麼做,才是真正向費曼致敬?我想答案是,我們應該盡可能把我們三明治中的大香腸拿掉,來向費曼致敬。

 

謝謝。

 

(掌聲)

 

以下為系統擷取之英文原文

About this talk

What's it like to be pals with a genius? Onstage at TEDxCaltech, physicist Leonard Susskind spins a few stories about his friendship with the legendary Richard Feynman, discussing his unconventional approach to problems both serious and ... less so.

About Leonard Susskind

Leonard Susskind works on string theory, quantum field theory, quantum statistical mechanics and quantum cosmology at Stanford. Full bio and more links

Transcript

I decided when I was asked to do this that what I really wanted to talk about was my friend Richard Feynman. I was one of the fortunate few that really did get to know him and enjoyed his presence. And I'm going to tell you the Richard Feynman that I knew. I'm sure there are other people here who could tell you about the Richard Feynman they knew, and it would probably be a different Richard Feynman.

Richard Feynman was a very complex man. He was a man of many, many parts. He was, of course, foremost a very, very, very great scientist. He was an actor. You saw him act. I also had the good fortune to be in those lectures, up in the balcony. They were fantastic. He was a philosopher; he was a drum player; he was a teacher par excellence. Richard Feynman was also a showman, an enormous showman. He was brash, irreverent -- he was full of macho, a kind of macho one-upsmanship. He loved intellectual battle. He had a gargantuan ego. But the man had somehow a lot of room at the bottom. And what I mean by that is a lot of room, in my case -- I can't speak for anybody else -- but in my case, a lot of room for another big ego. Well, not as big as his, but fairly big. I always felt good with Dick Feynman.

It was always fun to be with him. He always made me feel smart. How can somebody like that make you feel smart? Somehow he did. He made me feel smart. He made me feel he was smart. He made me feel we were both smart, and the two of us could solve any problem whatever. And in fact, we did sometimes do physics together. We never published a paper together, but we did have a lot of fun. He loved to win. With these little macho games we would sometimes play -- and he didn't only play them with me, he played them with all sorts of people -- he would almost always win. But when he didn't win, when he lost, he would laugh and seem to have just as much fun as if he had won.

I remember once he told me a story about a joke that the students played on him. They took him -- I think it was for his birthday -- they took him for lunch. They took him for lunch to a sandwich place in Pasadena. It may still exist; I don't know. Celebrity sandwiches was their thing. You could get a Marilyn Monroe sandwich. You could get a Humphrey Bogart sandwich. The students went there in advance, and they arranged that they would all order Feynman sandwiches. One after another, they came in and ordered Feynman sandwiches. Feynman loved this story. He told me this story, and he was really happy and laughing. When he finished the story, I said to him, "Dick, I wonder what would be the difference between a Feynman sandwich and a Susskind sandwich." And without skipping a beat at all, he said, "Well, they'd be about the same. The only difference is a Susskind sandwich would have a lot more ham," ham, as in bad actor. (Laughter) Well, I happened to have been very quick that day, and I said, "Yeah, but a lot less baloney."

(Laughter)

The truth of the matter is that a Feynman sandwich had a load of ham, but absolutely no baloney. What Feynman hated worse than anything else was intellectual pretense -- phoniness, false sophistication, jargon. I remember sometime during the 80s, the mid-80s, Dick and I and Sidney Coleman, we met a couple of times up in San Francisco at some very rich guy's house -- up in San Francisco for dinner. And the last time the rich guy invited us, he also invited a couple of philosophers. These guys were philosophers of mind. Their specialty was the philosophy of consciousness. And they were full of all kinds of jargon. I'm trying to remember the words -- "monism," "dualism," categories all over the place. I didn't know what those things meant, neither did Dick -- neither did Sydney for that matter.

And what did we talk about? Well, what do you talk about when you talk about minds? One thing, this one obvious thing to talk about -- can a machine become a mind? Can you build a machine that thinks like a human being, that is conscious? We sat around and we talked about this -- we of course never resolved it. But the trouble with the philosophers is that they were philosophizing when they should have been science-iphizing. It's a scientific question after all. And this was a very, very dangerous thing to do around Dick Feynman. Feynman let them have it -- both barrels, right between the eyes. It was brutal, it was funny -- ooh, it was funny. But it was really brutal. He really popped their balloon.

But the amazing thing was -- Feynman had to leave a little early. He wasn't feeling too well, so he left a little bit early. And Sidney and I were left there with the two philosophers. And the amazing thing is these guys were flying. They were so happy. They had met the great man; they had been instructed by the great man; they had an enormous amount of fun having their faces shoved in the mud; and it was something special. I realized there was something just extraordinary about Feynman, even when he did what he did.

Dick, he was my friend. I did call him Dick. Dick and I did have a little bit of a rapport. I think it may have been a special rapport that he and I had. We liked each other; we liked the same kind of things. I also liked the kind of intellectual macho games. Sometimes I would win, mostly he would win, but we both enjoyed them. And Dick became convinced at some point that he and I had some kind of similarity of personality. I don't think he was right. I think the only point of similarity between us is we both like to talk about ourselves. But he was convinced of this. And he was curious. The man was incredibly curious. And he wanted to understand what it was and why it was that there was this funny connection.

And one day we were walking. We were in France. We were in La Zouche. We were up in the mountains, 1976. We were up in the mountains, and Feynman said to me, he said, "Leonardo." The reason he called me Leonardo is because we were in Europe and he was practicing his French. And he said, "Leonardo, were you closer to your mother or to you father when you were a kid?" And I said, "Well, my real hero was my father. He was a working man, had a fifth grade education. He was a master mechanic, and he taught me how to use tools. He taught me all sorts of things about mechanical things. He even taught me the Pythagorean theorem. He didn't call it the hypotenuse, he called it the shortcut distance." And Feynman's eyes just opened up. He went off like a light bulb. And he said he had had basically the exact same relationship with his father. In fact, he had been convinced at one time that, to be a good physicist, that it was very important to have had that kind of relationship with your father. I apologize for the sexist conversation here, but this is the way it really happened.

He said that he had been absolutely convinced that this was necessary -- the necessary part of the growing up of a young physicist. Being Dick, he, of course, wanted to check this. He wanted to go out and do an experiment. So, well he did. He went out and did an experiment. He asked all his friends that he thought were good physicists, "Was it your mom or your pop that influenced you?" And to a man -- they were all men -- to a man, every single one of them said, "My mother." (Laughter) There went that theory down the trashcan of history. But he was very excited that he had finally met somebody who had the same experience with my father as he had with his father. And for some time, he was convinced that this was the reason we got along so well. I don't know. Maybe. Who knows?

But let me tell you a little bit about Feynman the physicist. Feynman's style -- no, style is not the right word. Style makes you think of the bow tie he might have worn or the suit he was wearing. There's something much deeper than that, but I can't think of another word for it. Feynman's scientific style was always to look for the simplest, most elementary solution to a problem that was possible. If it wasn't possible, you had to use something fancier. But no doubt part of this was his great joy and pleasure in showing people that he could think more simply than they could. But he also deeply believed, he truly believed, that if you couldn't explain something simply you didn't understand it. In the 1950s, people were trying to figure out how superfluid helium worked.

There was a theory. It was due to a Russian mathematical physicist, and it was a complicated theory. I'll tell you what that theory was soon enough. It was a terribly complicated theory full of very difficult integrals and formulas and mathematics and so forth. And it sort of worked, but it didn't work very well. The only way it worked is when the helium atoms were very, very far apart. The helium atoms had to be very far apart. And unfortunately, the helium atoms in liquid helium are right on top of each other.

Feynman decided, as a sort of amateur helium physicist, that he would try to figure it out. He had an idea, a very clear idea. He would try to figure out what the quantum wave function of this huge number of atoms looked like. He would try to visualize it, guided by a small number of simple principles. The small number of simple principles were very, very simple. The first one was that, when helium atoms touch each other, they repel. The implication of that is that the wave function has to go to zero, it has to vanish when the helium atoms touch each other. The other fact is that the ground state, the lowest energy state of a quantum system, the wave function is always very smooth -- has the minimum number of wiggles.

So he sat down -- and I imagine he had nothing more than a simple piece of paper and a pencil -- and he tried to write down, and did write down, the simplest function that he could think of which had the boundary conditions that the wave function vanish when things touch and is smooth in between. He wrote down a simple thing. It was so simple, in fact, that I suspect a really smart high school student, who didn't even have calculus, could understand what he wrote down. The thing was that that simple thing that he wrote down explained everything that was known at the time about liquid helium and then some.

I've always wondered whether the professionals, the real professional helium physicists, were just a little bit embarrassed by this. They had their super-powerful technique, and they couldn't do as well. Incidentally, I'll tell you what that super-powerful technique was. It was the technique of Feynman diagrams.

(Laughter)

He did it again in 1968. In 1968, in my own university -- I wasn't there at the time -- but in 1968, they were exploring the structure of the proton. The proton is obviously made of a whole bunch of little particles. This was more or less known. And the way to analyze it was, of course, Feynman diagrams. That's what Feynman diagrams were constructed for -- to understand particles. The experiments that were going on were very simple. You simply take the proton, and you hit it really sharply with an electron. This was the thing the Feynman diagrams were for. The only problem was that Feynman diagrams are complicated. They're difficult integrals. If you could do all of them, you would have a very precise theory. But you couldn't; they were just too complicated. People were trying to do them. You could do a one loop diagram. Don't worry about one loop. One loop, two loops -- maybe you could do a three loop diagram, but beyond that you couldn't do anything.

Feynman said, "Forget all of that. Just think of the proton as an assemblage of little particles -- a swarm of little particles." He called them partons. He called them partons. He said, "Just think of it as a swarm of partons moving real fast." Because they're moving real fast, relativity says the internal motions go very slow. The electron hits it suddenly. It's like taking a very sudden snapshot of the proton. What do you see? You see a frozen bunch of partons. They don't move, and because they don't move during the course of the experiment, you don't have to worry about how they're moving. You don't have to worry about the forces between them. You just get to think of it as a population of frozen partons. This was the key to analyzing these experiments. Extremely effective, it really did -- somebody said the word revolution is a bad word. I suppose it is, so I won't say revolution -- but it certainly evolved very, very deeply our understanding of the proton, and of particles beyond that.

Well, I had some more that I was going to tell you about my connection with Feynman, what he was like, but I see I have exactly half a minute. So I think I'll just finish up by saying I actually don't think Feynman would have liked this event. I think he would have said, "I don't need this." But how should we honor Feynman? How should we really honor Feynman? I think the answer is we should honor Feynman by getting as much baloney out of our own sandwiches as we can.

Thank you.

(Applause)
 


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