Ben Chen: Freeman Dyson: By the Book； Questions and answers with Freeman J. Dyson 2015.8.12〈從量子力學到太空文明——思索人類未來的人〉

Ben Chen

2016年2月16日 · The New York Times ·




Freeman Dyson談書和作家
本人著作中，最喜歡且有個人意義者：
“Disturbing the Universe” 《宇宙波瀾》第一本書.". I put my heart and soul into it. "而且在記憶猶新、感覺還在時完成之。「when memories were fresh and feelings still raw.」

對門外漢而言，最好的數學和物理書是哪一本？
都是舊書：
"Men of Mathematics,” by Eric Bell, published in 1937,
“Space, Time and Gravitation,” by Arthur Eddington, published in 1920.
Bell的書，吸引了那一代許多年輕人變成數學家。
Eddington的書，以一種可以理解的方式，讓愛因斯坦在歐美世界得到非常大的名聲，比在德國更有名。
他的傳記：
Maverick Genius: The Pioneering Odyssey of Freeman Dyson
原先和作者Phillip F. Schewe意見不合，不予合作。而且拒絕在出版之前先看內容。結果發現居然寫得比預期的好，兩人言歸於好。
Q:最欣賞的小說主角是哪一位？
A:The child Emily in “A High Wind in Jamaica,”
"在人類百萬年演化過程中，要在沒有法律的生存環境下得以存活下來，父母必須愛小孩，即使小孩做了很多壞事；小孩必須無情又可愛---"
"To have survived for millions of years in the lawless world of human evolution, parents must love children even when children do evil, and children must be ruthless and lovable. Emily is ruthless and lovable."

科學棋談

〈從量子力學到太空文明——思索人類未來的人〉

普林斯頓高等研究院，少數頂尖學者方能受邀進駐的學術殿堂。在這裡不須教書、不須產出論文，完全不受俗務干擾，只須專心思考；愛因斯坦、馮·紐曼、哥德爾、狄拉克、包立、李政道與楊振寧、……等大破大立的科學巨擘都曾在此駐足。在這柏拉圖天空的繁星之中，卻有一位連博士學位都沒有，而且不像其他學者來來去去，他一待就超過一甲子，直到2020年過世為止。

這位與眾不同的科學家就是今天恰逢百歲冥誕的戴森（Freeman Dyson）。他於1923年12月15日出生在英格蘭一個人口不到萬人的小鎮，自小嶄露數學天份，四歲時就曾試圖計算太陽有多少原子；他姊姊記得年幼的他總是被百科全書包圍著，不時埋首在紙上做計算。

戴森於1941年進入劍橋大學三一學院，但因第二次世界大戰戰情吃緊，他也加入空軍擔任分析師，直到戰爭結束後才重返校園取得大學文憑。1947年，戴森到美國康乃爾大學留學，跟著德裔物理學家貝特（Hans Bethe）做研究。戴森就是在這裡認識了大他五歲，卻已經擔任教授的費曼，兩人從此成為至交。

當時物理學家想要結合量子力學與狹義相對論，建立量子電動力學，以便正確描述光與帶電粒子間的交互作用，但是在計算過程中卻會產生無限大的數值，顯然與實際不符。為了解決這個問題，費曼在1948年發展出費曼圖來表述路徑積分，成功透過重整化抵消無限大。但是這種圖解的方式與傳統數學大相逕庭，令當代的物理學家感到愕然而難以接受；當時唯一的知音就只有戴森。

在此同時，哈佛大學教授施溫格（Julian S. Schwinger）與日本的朝永振一郎教授也各自以正統方法，發表重整化的方程式，只不過相當複雜。戴森很快看出他們的方程式和費曼圖可互相對應，兩者其實是一體的兩面，他於1949年發表論文，闡述兩者的連結，為量子電動力學的完備性補上臨門一腳。

最後費曼、施溫格與朝永振一郎三人共同獲頒1965年的諾貝爾物理學獎。施溫格與楊振寧都為戴森沒有得獎而大抱不平，但戴森自己倒是不以為意，他說：「如果你想贏得諾貝爾獎，就應該長期專注於某個深刻而重要的問題，至少十年不放。這可不是我的風格。」

是的，戴森在普林斯頓高等研究院中猶顯得風格迴異。院長歐本海默於1953年提供他終身職時，大概以為聘到一位量子力學的理論物理學家，不料三年後他就和氫彈之父泰勒一起合作，為通用動力公司設計絕對安全的核反應爐 TRIGA (因為溫度上升時，所使用的鈾氫鋯核燃料的反應速率反而會下降)。至今這種反應爐仍在世界各地的醫院、大學和研究機構使用中（我國清華大學校園內的核反應爐也是這型）。

1957年，戴森乾脆請假一年，跑去參加民間發起的獵戶座計畫，幫忙設計以核能為動力的火箭，用來探索太空。不過這計畫後來因為1963年的《部分禁止核試驗條約》國際公約而終止；戴森自己正是推動這項公約的主要人物之一，因為他見到美蘇的核武競賽越演越烈，寧可放棄核能的發展。

但戴森從未放棄探索宇宙的熱情。他除了寫過中子星、脈衝星等天文物理的論文，他還拋出許多極具創意的點子，例如在彗星上種植基因改造的樹(「戴森樹」，Dyson Tree)；只有一公斤重、可利用星塵為材料進行自我複製的自動機(「星雞」，Astrochicken) 適合漫長的太空旅行；還有將整個恆星包圍起來的「戴森球」(Dyson Sphere)，如此便可汲取恆星的所有熱輻射做為能源，供人類進行大規模的太空移民。

戴森曾引用哲學家柏林（Isaiah Berlin）的比喻，將偉大的科學家分成兩種：狐狸與刺蝟。他說：

「狐狸對每件事都感興趣，總是輕易地從一個問題跳到另一個問題。刺蝟只對少數他們認為是基本的問題感興趣，而且會花上數年或數十年的時間在同一個問題上。偉大發現大多是刺蝟找到的，多數小發現則是狐狸找到的。科學需要刺蝟也需要狐狸才能健康成長，刺蝟深入挖掘事物的本質，狐狸則探索我們這神奇宇宙的複雜細節。愛因斯坦是隻刺蝟，費曼則是隻狐狸。」

戴森當然也是狐狸，而且是隻眺望未來、思索人類文明何去何從的狐狸。

按：本文改寫自收錄於《 #科學史上的今天》的〈科學需要刺蝟，也需要狐狸〉

所有心情：

1717

Freeman Dyson: By the Book
The physicist, mathematician and author, most recently, of “Dreams of Earth and Sky” says the best books he knows about mathematics and physics are nearly a hundred years old.

MOBILE.NYTIMES.COM

Questions and answers with Freeman J. Dyson

What does the iconic physicist think about the Pluto flyby, the Iran nuclear deal, and how his scientific legacy might be affected by his contrarian climate-change views?

Jermey N. A. Matthews

12 八月 2015

Bookends:

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Now 91 years old, mathematical physicist Freeman Dyson continues to churn out fresh opinions and original ideas. He is well known for his contributions to quantum electrodynamics and random matrix theory, among other things. However, he also expresses broad views and visions in book reviews and essays, including on topics as varied as space exploration, genetic engineering, and nuclear weapons.

Freeman Dyson at the 2013 Dreams of Earth and Sky celebration in honor of his 90th birthday and 60th year as a professor at IAS. CREDIT: Andrea Kane

Two collections of Dyson’s writings were released earlier this year, within a month of each other: Dreams of Earth and Sky (New York Review of Books, 2015) and Birds and Frogs: Selected Papers, 1990–2014 (World Scientific, 2015). “One of the joys of both books is the pleasure of getting to know Dyson better,” writes theoretical physicist Frank Wilczek in his review for this month’s issue of Physics Today. Dreams of Earth and Sky, geared for the general reader, is a selection of Dyson’s reviews for the New York Review of Books. The second offering, Birds and Frogs “is more varied and on the whole more technical,” writes Wilczek.

Physics Today caught up with Dyson recently to talk about his new books and about his views on current issues.

PT: What prompted you to assemble these two collections around the same time? And what's new or different about them?

DYSON: The simultaneous publication of the two books was unexpected and unplanned.Dreams of Earth and Sky is a collection of book reviews published by the New York Review of Books. It is a sequel to The Scientist as Rebel (New York Review Collections, 2006). Birds and Frogs is a collection of writings—everything except for book reviews—published by World Scientific. It is a sequel to an earlier volume of selected papers published by the American Mathematical Society.

PT: The reviewer highlights your appreciation for the virtues of blunders and of wrong theories. At what point in your career did you begin developing these appreciations?

DYSON: I did not think much about blunders and wrong theories until I read the books by Mario Livio (Brilliant Blunders, Simon & Schuster, 2013) and Margaret Wertheim (Physics on the Fringe, Walker Books, 2011) and wrote reviews of them. Writing reviews gives me a chance to think new thoughts and express new opinions. Sometimes the opinions are sincere and sometimes not. Reviews are intended to entertain as well as educate.

PT: Three hot topics in the news right now are the Pluto flyby, the Iran nuclear deal, and thenew $100 million SETI initiative. What, briefly, is your reaction to each of these issues? And what do you say about them in your new books?

DYSON: My reaction to the Pluto flyby: A magnificent achievement. It will take a year and a half to send back to Earth the information collected in a couple of days. We will not know what we have discovered until the information comes back.

My reaction to the nuclear deal with Iran: Enthusiastic approval. This was long overdue. Iran is like China, an ancient and gifted civilization, to be treated with respect even when we disagree. It is far better for us to learn to live with them as equals rather than to tell them how to behave.

My reaction to the Milner SETI initiative: A mixture of good and bad. It is good to keep SETI observations going ahead at a sustainable level. It is bad to give the public the impression that this cannot be done for less than a hundred million dollars. I have in mind the unfortunate history of Bob Forward's Project Cyclops. Cyclops gave the public the wrong idea that SETI was an expensive and extravagant folly, with the result that sustained support of SETI became more difficult. There is one important difference between Milner and Forward. Milner is supporting his project with real money. Forward did not.

I said nothing in the new books about any of these three topics.

PT: Are you ever concerned that your contrarian view of climate science will become as much a part of your legacy as all the other contributions you’ve made to science? Or do you embrace that possibility?

DYSON: I do not care what my legacy will be. To me the most beautiful aspect of science is that it is a collaborative enterprise, with a multitude of people from all over the world taking part. In the long run, it does not matter who discovered what. We all share the joy of discovery even if we do not share the credit. I am happy to be skeptical about the prevailing dogma concerning climate change, whether or not it turns out that I am right. As a scientist, I can disagree vigorously with my colleagues and still remain friends.

PT: What projects—a book or something else, personal or professional—do you have on the horizon?

DYSON: My next publishing project is a book of letters. My mother preserved the weekly letters that I wrote to her as a dutiful son for 30 years. These letters contain a record of historic events as they appeared at the time, without the distortion of hindsight. I still need to select and edit the letters, and to write comments to explain the context and identify the characters. After that, I have no plans.

PT: What books are you currently reading?

DYSON: The last three books that I have read were biographies of famous physicists. I wrote reviews of all of them for the New York Review of Books, too late to be included in Dreams of Earth and Sky. I recommend all of them to readers of Physics Today. They are Half-life: The Divided Life of Bruno Pontecorvo (Basic Books, 2015) by Frank Close, Einstein: His Space and Times (Yale University Press, 2015) by Steven Gimbel, and Planck: Driven by Vision, Broken by War (Oxford University Press, 2015) by Brandon Brown.

By a remarkable coincidence, these three lives exemplify precisely the three alternatives described by my late colleague [the economist] Albert Hirschman in his classic book, Exit, Voice, and Loyalty: Responses to Decline in Firms, Organizations, and States (Harvard University Press, 1970). Hirschman is discussing the three possible responses of a person who belongs to a big organization where things are going badly. Exit means giving up the struggle to influence events. Voice means standing firm and speaking out against evil. Loyalty means keeping quiet and making compromises with evil. Pontecorvo chose exit, Einstein chose voice, and Planck chose loyalty. Each of them paid the price for his choice, just as Hirschman described it.

For more about Dyson, you can read the recent biography Maverick Genius (Thomas Dunne Books/St. Martin’s Press, 2013) by Phillip Schewe and the Physics Today review of that book.