在我们的盛邀之下，杨先生回顾了他在念本科和研究生阶段的经历和经验。他讲述了当时西南联大的情况，提到了清华与庚子赔款，也提到了当时中国屈辱的历史。他特别强调他当时与两位同学一起兼职教书，经常天南海北的讨论许多问题，他觉得这种讨论非常有益处，有利于真正弄懂学过的东西。杨先生说，他们当时发明了一个名词，说学物理有两种方式，一种是空中看，一种是趴着看。如果一直趴着看，就不能清楚整个的位置。但趴着看也是必要的。对任何东西的了解都是有一部分是趴着看，看得多了才可以有从空中看的能力。

杨先生说，他在西南联大的学习是非常扎实的。他那时的老师给他最大的受益就是严谨细致的作风，深厚的理论功底。而在他去美国之后的导师费米、泰勒，则是另一种风格。他们讲课不那么认真，但每天想的都是前沿的问题。杨先生评价说，泰勒每天可能有10个想法，9个半都是错的，但有半个对的就不得了。杨先生建议我们在中国式的扎实根基的基础上，多学习渗透式的学习方法，胆子大一点，不要严格划清”学过的”和”没学的”界限，局限于”知之为知之，不知为不知”的中国式学习方法。

杨先生提醒我们，中国人作实验也是做得很好的。那种认为中国人不会动手的偏见是错误的。许多人去美国的时候以为自己不会动手，其实只是没有试过。现在理论考试考的好，不一定代表你最合适的方向是理论物理。关于作实验，杨先生还回忆了他在美国作研究生的经历，杨先生说，他做了一年多实验，有一个收获是他对于做实验物理的人有了一些了解，知道了做实验物理的人在想什么，着急什么，这一点使杨先生在那以后能够与实验物理学家紧密接触，了解他们的成果，为实验物理学家提出新的建议。

在杨先生近半个小时的讲话之后，我们也提出了一些自己关心的问题。

关于学习英语，杨先生说，学英语有两个重要的方面，一是发音，一是单词。他说，对于发音，最好的办法是每天大声朗诵10分钟，把一段3分钟的文章念3遍。而提高单词量的最好方法是读小说和报纸，不要查字典，硬着头皮坚持去猜单词的意思。他当年这样看了两本书以后，英文有了很显著的提高。

我们的第二个问题是关于科学技术在当今的双重作用。杨先生语重心长的说：”首先我希望你们了解，你们生活在一个大时代里，这个大时代有两重的含义。一是指人类的生产力发展，因为现在真正学会了用科技。回顾一下一百年前，那时也有很多聪明的人，比较先进的技术，但对于转化成生产力，还做得不好。现在全世界都已经意识到科学技术的作用，而这还只是开始。这个发展不是你们个人的问题，而是全世界的发展方向。这个发展一定会使得世界的生产力继续进步，也一定会使中华民族在世界上的地位进一步提高。如果你们能够对以后人类的生产力通过科技的发展继续推进，尤其是能够为中华民族的继续发展作出贡献，我想你就可以说在你一生中作出了非常重要的事情。另一方面，科技的发展也带来了无数的、有些是现在还想不清楚的问题，这些问题几十年后毫无疑问会成为对整个人类的挑战。我想这一点是每个人都值得注意的。了解到现在是一个对整个人类的历史、中华民族的历史是一个非常重要的时代，是每个人都应该深深记在脑子里的。”

第三个问题是对于学物理的人转行的看法。杨先生认为学物理的人适应面的确很广，也应该多涉猎一些方面。他幽默地说，古人说”狡兔三窟”，我看即使不用三窟，至少不能只钻进一个方向里去。

关于物理学的价值观 

      物理学发展到今天已是一门很广泛的学问，其中有很多美妙的东西，可是这并不是每个人都能一一体会到的，这由于各人背景不同，也是很自然的事。各人的价值观念中也并不一定都是正确的，比如我喜欢的有些将来是有发展的，有些将来是没有发展的。但是价值观是必要的，这是决定你事业发展方向的基础，以及用什么方法去研究问题。从学术气氛很好的大学毕业出来的研究生当中，二十年后每个人的成就很不一样，这就是有人走对了路，有人走错了路。走对了路的人是大有发展的，走错路的人既便花很大力气也收效甚微。当然走哪条路不仅与自己的主观判断有关，还得要有机会。例如在一个大学中，没有一个教授的研究领域让你觉得是大有发展而且你又喜欢的，你就不应该在这个大学发展。因此，我认为一个人在做研究生的时候，价值观念对他的事业发展有决定性的影响。等到你自己做研究工作的时候向哪个方向进军，这就看你在念书的时候所培养出来的品味和价值判断。 

      我给大家的另一个建议是，兴趣不要太窄。我占了一个非常大的便宜，是因为我一方面在做基本粒子物理或者叫做高能物理研究，另一方面我又对统计物理很有兴趣。一个人能够跨两个学科有很多好处：一个好处是因为做研究时一般不可能马上取得势如破竹的成功，多半的时候是做不出来，很苦恼，如果另一个方向有兴趣的话则可以去干一干，反而有些成果，可以调节你自己的心理状态；另外，不同的领域常常可有互相借鉴之处，交叉渗透。例如，高能物理和统计力学在50年代是没有关系的。当时我在普林斯顿高等研究所工作，头一年做高能物理，第二年开始做统计物理，做得很成功，我那时候写的三篇文章都是那个领域的经典之作。有些原本看起来是没有关系的领域，可能走到更深一层是一回事情。假如一个人对两个领域都了解的话，那么他就有可能做出重要的贡献。20世纪末的各种领域，不仅是物理学内部，也包括生物学、信息科学，化学都要交叉渗透，假如一个人兴趣广的话，可以做出重要的贡献。我再举一个简单的例子，比如你们生病的时候，要用CATScan(计算机辅助层析扫描)。它的发明人之一是一个理论物理学家，他因为对计算机发生兴趣，对医学也有兴趣，又是理论物理学家，就把这些领域结合起来，因此发明了CATscan的原理。所以我想，在很早的时候就对好几个领域发生兴趣是一个好的开端。 

东西方教育方式的比较 

      关于东西方教育各自的长处、短处，我认为是一个很重要的问题，曾经思考过很长时间。我曾在西南联大受过很好的教育，这对我一生受用无穷；我在芝加哥大学攻读博士学位的两年半期间，也学到了很多东西。我感到，在东西方教育的环境中所学到的东西确有很大的分别，我想我很幸运得到两方面的收益。 

      我在西南联大时念的是书本上的知识，按照中国的教育传统，老师都是很负责任的。当时教授我量子力学的是王竹溪先生，我所记的笔记都是非常系统化、非常深入的。芝加哥大学是学季制度(quarterssystem)，我也选了一个量子力学，是泰勒(Taylor)所教的，泰勒当时三十多岁，已经很有名望，后来他成了“氢弹之父”。我发现他的教法与王先生的教法完全不一样，王先生总是事先准备得很好，讲义写下来是很扎实的。而泰勒非常之忙，我们觉得他很多时候根本没准备。我已经学过这个课，所以他讲的东西我多半都知道。有时候我看见他“误入歧途”，想出一个方法，后来又推翻。初学者或许不喜欢他的讲课方式，看着有点乱七八糟的，你不知道他现在讲的呆一会儿是不是又说不对了。可是我看起来很有启发。我看到了泰勒想力图走出困境的摸索过程。他不是急于知道这个公式是否是从另一个公式导出，而是要了解一个物理的形象，比如他对分子跟原子物理中的选择规则有直觉的感觉。所以，我认识到中国的教育是用逻辑的方法，不太注意直觉；而泰勒的学习是直觉式的，他常常不能告诉你他思考的逻辑步骤。我得出的结论是，这两种办法都非常重要。 

　　所以，总结一下中国与美国的教育方法(尤其是与美国一些物理学家的学习思想方法)的不同点，中国是一步一步走，而象泰勒是注重直觉。这两种方法都很重要。一个人最好能训练成两种能力兼备，既有直觉，又能将其用逻辑的步骤推理出来，将有助于更深地理解事物。我曾在一篇文章中说，中国的教育方法是推导式的，先将最基本的物理定理告诉学生，让他们一步一步推演下去；美国则是归纳式的，不是从基本原则开始，而是从现象开始，再从中提取其精神。如果一个人对这两种方法融汇贯通就好了。

　学习数学与学习物理的关系 

      数学和物理学都是很重要的，两方面都比较强的同学很容易对于该侧重哪方面学习觉得迷惑：如果选择了物理，数学学到什么程度不至于拖物理的后腿；如果选择数学，许多物理知识是否可以不学了?这与我刚才谈到的自己的价值观有很大的关系。我可以举一个简单的例子。我在清华园生活时，我父亲在科学馆有一个办公室，暑假时他就常叫我到他的办公室，教我一点数学问题，等差级数啦、“鸡兔同笼”啦……等到我在美国教育孩子时也教他们，他们也学得很快，但是他们与我不同的地方是，他们学会一年以后我再去问他们，已经忘得干干净净了。可是我记得很清楚，这因为我当时学习的时候有一种奇妙的感受，这种感受促使我去牢牢记住它。这就是一个最基础的价值观–如果你认为你在这个方面有所天赋，就值得多下功夫。 

      我认为算学是很奇妙的一门学问。20世纪的数学变化无穷，在不同的领域数学家们发现了一些规律，并把它们合并在一起，例如数论讲的东西是讨论离散的问题，而拓扑学讨论的是连续的。可是近几十年来，数学家们发现离散同连续有很大关系，这是一个重要的方向。近三四十年来还发现，数学与理论物理有着极为密切的关系。不过数学家的价值观与物理学家的价值观是不一样的。虽然在很多重要的领域物理学与数学是结合在一起的，但是二者的研究方向和它的传统是截然不同的。如果你的兴趣在于物理，那么对于物理与数学的共同领域应当从物理的价值观出发去认识。数学有很大的引诱力，一个人研究数学可以被它迷住，也就是完全接受了数学的价值观，这样的人不适合研究物理，这是因为他的思路已经同做物理研究的人不一样了。这样的话他最好放弃他做物理研究的初衷，干脆研究数学。我认为如果一个人有志于物理，数学确实不必研究太深。有一个物理学家叫费曼，他讲话容易过火，他说数学对于物理没用，物理学家所需要的数学一个星期便可发明出来，用不着去专门学数学。这话虽过火，但也有点道理。我在西南联大时学过高等微积分，还看了一些现代分析学的书，学过一门数理统计的课，到芝大以后就没有再念很多的数学，只念过一个学期陈省身先生教的微分几何。后来到了做研究的时候，我自己又学了一些椭圆型方程和李群论。我认为搞理论物理的人数学学到某种程度就可以了，到需要的时候再去补一些新知识，这是最容易成功的道路。 

理论物理与实验物理

      三四十年以前，外国人对中国人有个印象，就是中国人不会动手，只会搞理论研究。比如台湾50年代的许多学生到美国去，都是学理论物理。可是今天已完全不是这么回事，现在美国科学院院士中，在物理方面，中国血统的人不止15人，绝大多数都是做实验的。这个原因是当初有一个错误的印象，许多人之所以去学习理论物理，不是因为不会做实验物理，是因他们没有接触过实验物理，没有经验，许多人自然而然就想学理论物理，但实际上他们改做实验物理做得很好，所以才会有这么多美国科学院院士。丁肇中从台湾过去是去念理论物理的，后来遇到一个有名的物理学家–密歇根大学教授乌伦贝克，说物理还是以实验为基础，于是改行搞实验物理，后来大有成就。现在，许多中国血统的优秀实验物理学家当初都是想学理论的。如果同学们是斟酌自己是做理论物理还是做实验物理时，我想不要因为自己没有实验经验就不敢碰实验物理。

http://www.nytimes.com/2007/12/19/education/19physics.html?_r=1&hp&oref=slogin

Erik Jacobs for The New York Times

Prof. Walter H. G. Lewin, No. 1 on the most downloaded list at iTunes U for a while, with objects he uses for his physics lessons.

• comments
• Sign In to E-Mail or Save This
• Print
• Share
  • Del.icio.us
  • Digg
  • Facebook
  • Newsvine
  • Permalink

By SARA RIMER

Published: December 19, 2007

CAMBRIDGE, Mass. — Walter H. G. Lewin, 71, a physics professor, has long had a cult following at M.I.T. And he has now emerged as an international Internet guru, thanks to the global classroom the institute created to spread knowledge through cyberspace.

Skip to next paragraph

Web Lectures

Here are links to some of Professor Lewin’s online physics lectures.

• A Demonstration of Electrostatics
• Trajectories of Objects in Freefall
• How a Rocket Lifts Off
• A Lecture on Pendulums

Enlarge This Image

Courtesy Markos Hankin and M.I.T.

Professor Lewin demonstrates physics of pendulums.

Readers’ Comments

What do you think of taking classes online?

• Post a Comment »

Professor Lewin’s videotaped physics lectures, free online on the OpenCourseWare of the Massachusetts Institute of Technology, have won him devotees across the country and beyond who stuff his e-mail in-box with praise.

“Through your inspiring video lectures i have managed to see just how BEAUTIFUL Physics is, both astounding and simple,” a 17-year-old from India e-mailed recently.

Steve Boigon, 62, a florist from San Diego, wrote, “I walk with a new spring in my step and I look at life through physics-colored eyes.”

Professor Lewin delivers his lectures with the panache of Julia Child bringing French cooking to amateurs and the zany theatricality of YouTube’s greatest hits. He is part of a new generation of academic stars who hold forth in cyberspace on their college Web sites and even, without charge, on iTunes U, which went up in May on Apple’s iTunes Store.

In his lectures at ocw.mit.edu, Professor Lewin beats a student with cat fur to demonstrate electrostatics. Wearing shorts, sandals with socks and a pith helmet — nerd safari garb — he fires a cannon loaded with a golf ball at a stuffed monkey wearing a bulletproof vest to demonstrate the trajectories of objects in free fall.

He rides a fire-extinguisher-propelled tricycle across his classroom to show how a rocket lifts off.

He was No. 1 on the most downloaded list at iTunes U for a while, but that lineup constantly evolves. The stars this week included Hubert Dreyfus, a philosophy professor at the University of California, Berkeley, and Leonard Susskind, a professor of quantum mechanics at Stanford.

Last week, Yale put some of its most popular undergraduate courses and professors online free. The list includes Controversies in Astrophysics with Charles Bailyn, Modern Poetry with Langdon Hammer and Introduction to the Old Testament with Christine Hayes.

M.I.T. recently expanded its online classes by opening a site aimed at high school students and teachers. Judging from his fan e-mail, Professor Lewin, who is among those featured on the new site, appeals to students of all ages.

Some of his correspondents compare him to Richard Feynman, the free-spirited, bongo-playing Nobel laureate who popularized physics through his books, lectures and television appearances.

With his wiry grayish-brown hair, his tortoiseshell glasses and his intensity, Professor Lewin is the iconic brilliant scientist. But like Julia Child, he is at once larger than life and totally accessible.

“We have here the mother of all pendulums!” he declares, hoisting his 6-foot-2, 170-pound self on a 30-pound steel ball attached to a pendulum hanging from the ceiling. He swings across the stage, holding himself nearly horizontal as his hair blows in the breeze he created.

The point: that a period of a pendulum is independent of the mass — the steel ball, plus one professor — hanging from it.

“Physics works!” Professor Lewin shouts, as the classroom explodes in cheers.

“Hi, Prof. Lewin!!” a fan who identified himself as a 17-year-old from China wrote. “I love your inspiring lectures and I love MIT!!!”

A fan who said he was a physics teacher from Iraq gushed: “You are now my Scientific Father. In spite of the bad occupation and war against my lovely IRAQ, you made me love USA because you are there and MIT is there.”

Professor Lewin revels in his fan mail and in the idea that he is spreading the love of physics. “Teaching is my life,” he said.

The professor, who is from the Netherlands, said that teaching a required course in introductory physics to M.I.T. students made him realize “that what really counts is to make them love physics, to make them love science.”

He said he spent 25 hours preparing each new lecture, choreographing every detail and stripping out every extra sentence.

“Clarity is the word,” he said.

Fun also matters. In another lecture on pendulums, he stands back against the wall, holding a steel ball at the end of a pendulum just beneath his chin. He has just demonstrated how potential energy turns into kinetic energy by sending the ball flying across the stage, shattering a pane of glass he had bolted to the wall.

Now he will demonstrate the conservation of energy.

“I am such a strong believer in the conservation of energy that I am willing to risk my life for it,” he says. “If I am wrong, then this will be my last lecture.”

He closes his eyes, and releases the ball. It flies back and forth, stopping just short of his chin.

“Physics works!” Professor Lewin shouts. “And I’m still alive!”

Chasing rainbows hooked Mr. Boigon, the San Diego florist. He was vacationing in Hawaii when he noticed the rainbow outside his hotel every afternoon. Why were the colors always in the same order?

When he returned home, Mr. Boigon said in a telephone interview, he Googled rainbows. Within moments, he was whisked to M.I.T. Lecture Hall No. 26-100. Professor Lewin was in front of a few hundred students.

“All of you have looked at rainbows,” he begins. “But very few of you have ever seen one. Seeing is different than looking. Today we are going to see a rainbow.”

For 50 minutes, he bounds across the stage, writing equations on the blackboard and rhapsodizing about the “amazing” and “beautiful” physics of rainbows. He explains how the colors always appear in the same order because of how light refracts and reflects in the water droplets.

For the finale, he creates a rainbow by shining a bright light into a glass sphere containing a single drop of water.

“There it is!” Professor Lewin cries.

“Your life will never be the same,” he tells his students. “Because of your knowledge, you will be able to see way more than just the beauty of the bows that everyone else can see.”

“Professor Lewin was correct,” Mr. Boigon wrote in an e-mail message to a reporter. “He made me SEE … and it has changed my life for the better!!”

“I had never taken a course in physics, or calculus, or differential equations,” he wrote to Professor Lewin. “Now I have done all that in order to be able to follow your lectures. I knew the name Isaac Newton, but nothing about Newtonian Mechanics. I had heard of the likes of Einstein, Galileo.” But, he added that he “didn’t have a clue on earth as to what they were all about.”

“I walk down the street analyzing the force of a boy on skateboard or the recoil of a carpenter using a nail gun,” he wrote. “Thank you with all my heart.”

http://www.nytimes.com/2007/12/19/education/19physics.html?_r=1&hp&oref=slogin

Erik Jacobs for The New York Times

Prof. Walter H. G. Lewin, No. 1 on the most downloaded list at iTunes U for a while, with objects he uses for his physics lessons.

• comments
• Sign In to E-Mail or Save This
• Print
• Share
  • Del.icio.us
  • Digg
  • Facebook
  • Newsvine
  • Permalink

By SARA RIMER

Published: December 19, 2007

CAMBRIDGE, Mass. — Walter H. G. Lewin, 71, a physics professor, has long had a cult following at M.I.T. And he has now emerged as an international Internet guru, thanks to the global classroom the institute created to spread knowledge through cyberspace.

Skip to next paragraph

Web Lectures

Here are links to some of Professor Lewin’s online physics lectures.

• A Demonstration of Electrostatics
• Trajectories of Objects in Freefall
• How a Rocket Lifts Off
• A Lecture on Pendulums

Enlarge This Image

Courtesy Markos Hankin and M.I.T.

Professor Lewin demonstrates physics of pendulums.

Readers’ Comments

What do you think of taking classes online?

• Post a Comment »

Professor Lewin’s videotaped physics lectures, free online on the OpenCourseWare of the Massachusetts Institute of Technology, have won him devotees across the country and beyond who stuff his e-mail in-box with praise.

“Through your inspiring video lectures i have managed to see just how BEAUTIFUL Physics is, both astounding and simple,” a 17-year-old from India e-mailed recently.

Steve Boigon, 62, a florist from San Diego, wrote, “I walk with a new spring in my step and I look at life through physics-colored eyes.”

Professor Lewin delivers his lectures with the panache of Julia Child bringing French cooking to amateurs and the zany theatricality of YouTube’s greatest hits. He is part of a new generation of academic stars who hold forth in cyberspace on their college Web sites and even, without charge, on iTunes U, which went up in May on Apple’s iTunes Store.

In his lectures at ocw.mit.edu, Professor Lewin beats a student with cat fur to demonstrate electrostatics. Wearing shorts, sandals with socks and a pith helmet — nerd safari garb — he fires a cannon loaded with a golf ball at a stuffed monkey wearing a bulletproof vest to demonstrate the trajectories of objects in free fall.

He rides a fire-extinguisher-propelled tricycle across his classroom to show how a rocket lifts off.

He was No. 1 on the most downloaded list at iTunes U for a while, but that lineup constantly evolves. The stars this week included Hubert Dreyfus, a philosophy professor at the University of California, Berkeley, and Leonard Susskind, a professor of quantum mechanics at Stanford.

Last week, Yale put some of its most popular undergraduate courses and professors online free. The list includes Controversies in Astrophysics with Charles Bailyn, Modern Poetry with Langdon Hammer and Introduction to the Old Testament with Christine Hayes.

M.I.T. recently expanded its online classes by opening a site aimed at high school students and teachers. Judging from his fan e-mail, Professor Lewin, who is among those featured on the new site, appeals to students of all ages.

Some of his correspondents compare him to Richard Feynman, the free-spirited, bongo-playing Nobel laureate who popularized physics through his books, lectures and television appearances.

With his wiry grayish-brown hair, his tortoiseshell glasses and his intensity, Professor Lewin is the iconic brilliant scientist. But like Julia Child, he is at once larger than life and totally accessible.

“We have here the mother of all pendulums!” he declares, hoisting his 6-foot-2, 170-pound self on a 30-pound steel ball attached to a pendulum hanging from the ceiling. He swings across the stage, holding himself nearly horizontal as his hair blows in the breeze he created.

The point: that a period of a pendulum is independent of the mass — the steel ball, plus one professor — hanging from it.

“Physics works!” Professor Lewin shouts, as the classroom explodes in cheers.

“Hi, Prof. Lewin!!” a fan who identified himself as a 17-year-old from China wrote. “I love your inspiring lectures and I love MIT!!!”

A fan who said he was a physics teacher from Iraq gushed: “You are now my Scientific Father. In spite of the bad occupation and war against my lovely IRAQ, you made me love USA because you are there and MIT is there.”

Professor Lewin revels in his fan mail and in the idea that he is spreading the love of physics. “Teaching is my life,” he said.

The professor, who is from the Netherlands, said that teaching a required course in introductory physics to M.I.T. students made him realize “that what really counts is to make them love physics, to make them love science.”

He said he spent 25 hours preparing each new lecture, choreographing every detail and stripping out every extra sentence.

“Clarity is the word,” he said.

Fun also matters. In another lecture on pendulums, he stands back against the wall, holding a steel ball at the end of a pendulum just beneath his chin. He has just demonstrated how potential energy turns into kinetic energy by sending the ball flying across the stage, shattering a pane of glass he had bolted to the wall.

Now he will demonstrate the conservation of energy.

“I am such a strong believer in the conservation of energy that I am willing to risk my life for it,” he says. “If I am wrong, then this will be my last lecture.”

He closes his eyes, and releases the ball. It flies back and forth, stopping just short of his chin.

“Physics works!” Professor Lewin shouts. “And I’m still alive!”

Chasing rainbows hooked Mr. Boigon, the San Diego florist. He was vacationing in Hawaii when he noticed the rainbow outside his hotel every afternoon. Why were the colors always in the same order?

When he returned home, Mr. Boigon said in a telephone interview, he Googled rainbows. Within moments, he was whisked to M.I.T. Lecture Hall No. 26-100. Professor Lewin was in front of a few hundred students.

“All of you have looked at rainbows,” he begins. “But very few of you have ever seen one. Seeing is different than looking. Today we are going to see a rainbow.”

For 50 minutes, he bounds across the stage, writing equations on the blackboard and rhapsodizing about the “amazing” and “beautiful” physics of rainbows. He explains how the colors always appear in the same order because of how light refracts and reflects in the water droplets.

For the finale, he creates a rainbow by shining a bright light into a glass sphere containing a single drop of water.

“There it is!” Professor Lewin cries.

“Your life will never be the same,” he tells his students. “Because of your knowledge, you will be able to see way more than just the beauty of the bows that everyone else can see.”

“Professor Lewin was correct,” Mr. Boigon wrote in an e-mail message to a reporter. “He made me SEE … and it has changed my life for the better!!”

“I had never taken a course in physics, or calculus, or differential equations,” he wrote to Professor Lewin. “Now I have done all that in order to be able to follow your lectures. I knew the name Isaac Newton, but nothing about Newtonian Mechanics. I had heard of the likes of Einstein, Galileo.” But, he added that he “didn’t have a clue on earth as to what they were all about.”

“I walk down the street analyzing the force of a boy on skateboard or the recoil of a carpenter using a nail gun,” he wrote. “Thank you with all my heart.”