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Was Aristotle the first physicist?

March 11th, 2008

Aristotle’s Lyceum provided the world’s first comprehensive set of courses on all aspects of knowledge. Although the little room where Aristotle probably taught had space for perhaps just 10 students, the scope of the courses that he gave there, which miraculously survive today in some 30 books of his lecture notes, was phenomenal. It is hard to believe they were written by a single person.

Aristotle had an extraordinary range of interests and learning. His courses included philosophy, logic, astronomy, physics, biology, meteorology, poetry, drama, ethics, politics, psychology and economics - in fact, many of the subjects of a modern university. Some of his biological insights were not rediscovered until the 19th century and his logic was not superseded until the work of Gottlob Frege in the early part of the 20th century.

Born in northern Greece in 384 BC, Aristotle’s ideas dominated western science and philosophy for nearly 2000 years, from his death in 322 BC until Galileo’s destruction of his mechanics in 1609. Unfortunately, with the rise of modern physics over the past three centuries, Aristotle’s achievements have been eclipsed. We honour the thinkers of antiquity who guessed right - the atomic theory of Democritus, the heliocentric view of Aristarchus - but not the man who we can truly say invented science. For his physics and astronomy, Aristotle has become identified as the barrier to scientific progress in the renaissance.

After he died, Aristotle’s books, which represent perhaps just one-third of his total output, are said to have been buried in a cave in Asia Minor for 200 years. Although the Peripatetic philosopher Andronicus did prepare an edition of Aristotle’s works in Rome shortly after their rediscovery, they were entirely lost to Europe following the fall of the Roman empire. It was not until the 11th and 12th centuries - thanks to Arabic translations from the Islamic kingdoms of Sicily and Spain - that his writings were rediscovered in Europe.

摘自:http://physicsworld.com/cws/article/print/3494

What is Science

March 7th, 2008

Science (from the Latin scientia, ‘knowledge’), in the broadest sense, refers to any systematic knowledge or practice. Examples of the broader use included political science and computer science, which are not incorrectly named, but rather named according to the older and more general use of the word. In a more restricted sense, science refers to a system of acquiring knowledge based on the scientific method, as well as to the organized body of knowledge gained through such research.

Fields of science are commonly classified along two major lines: Natural sciences, which study natural phenomena (including biological life), and Social sciences, which study human behavior and societies.

These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.

Mathematics, which is sometimes classified within a third group of science called formal science, has both similarities and differences with the natural and social sciences. It is similar to empirical sciences in that it involves an objective, careful and systematic study of an area of knowledge; it is different because of its method of verifying its knowledge, using a priori rather than empirical methods. Formal science, which also includes statistics and logic, is vital to the empirical sciences. Major advances in formal science have often led to major advances in the physical and biological sciences. The formal sciences are essential in the formation of hypotheses, theories, and laws, both in discovering and describing how things work (natural sciences) and how people think and act (social sciences).

The word science comes through the Old French, and is derived from the Latin word scientia for knowledge, which in turn comes from scio. ‘I know’. The Indo-European root means to discern or to separate, akin to Greek schizein, to split, Latin scindere, to split. From the Middle Ages to the Enlightenment, science or scientia meant any systematic recorded knowledge. Science therefore had the same sort of very broad meaning that philosophy had at that time. In other languages, including French, Spanish, Portuguese, and Italian, the word corresponding to science also carries this meaning.

From classical times until the advent of the modern era, “philosophy” was roughly divided into natural philosophy and moral philosophy. In the 1800s, the term natural philosophy gradually gave way to the term natural science. Natural science was gradually specialized to its current domain, which typically includes the physical sciences and biological sciences. The social sciences, inheriting portions of the realm of moral philosophy, are currently also included under the auspices of science to the extent that these disciplines use empirical methods. As currently understood, moral philosophy still retains the study of ethics, regarded as a branch of philosophy.

Today, the primary meaning of “science” is generally limited to empirical study involving use of the scientific method.

摘录自:http://www.answers.com/science

量子多体参考书

March 2nd, 2008

这些书我都有纸版。

  1. 蔡建华,龚昌德等,《量子统计的格林函数理论》
  2. Fetter, Walecka, 《多粒子系统的量子理论》,Quantum Theory of Many Particle Systems (1971)
  3. A. A. Abrikosov 等,《统计物理学中的量子场论方法》
  4. G. D. Mahan, Many-Particle Physics
  5. J. W. Negele, Henri Orland, Quantum Many-Particle Systems
  6. Nato Nagaosa, Quantum Field Theory in Condensed Matter Physics
  7. 文小刚,《量子多体理论》

2008春季课表

March 2nd, 2008

量子多体:(第1-9周),周三下午 13:30 - 15:15,学楼409;周五下午 15:30 - 17:15,学楼107
自然科学史:(第2-13周),周三晚上 19:00 - 21:50,逸夫楼 404

我手上的一些《生物物理》参考书

January 26th, 2008

以下是我收集的一些《生物物理》方面参考书,不包括电子版。

Physics and Biology, M.V. Volkenstein (1982)

一本很精炼的概念书,国内有中文版;

生物物理学,赵南明等(2000)

不多的以生物物理为书名的中文书,适合研究生或本科生学习的入门书;

Mathematical Biology, J.D. Murray 2nd edition (1998)

已经是生物数学了,讨论了不少相关数学模型,大多属于微分方程或偏微分方程;

软物质物理学导论,陆坤权等(2006)

书名叫软物质,某些章节属于生物物理方面的,适合相关领域研究生入门阅读;

生物物理学概论,W. 休斯(1979)

这是我从yijun处借来的,一本很老的书,复旦大学译。

亚洲狮 vs 华南虎

January 10th, 2008

亚洲狮是印度的国宝,目前仅在印度的吉尔森林中有300头野生亚洲狮,当然世界各地动物园里还会有不少圈养的。从这一点亚洲狮比华南虎幸运的多,300头可不是个小数字。

这300 头狮子绝大多数生活在1450平方公里的保护区内,是上世纪初由一位印度王子保护的,起初只有12头狮子。这300头狮子的基因是高度趋同的,如果作 DNA鉴定的话,它们就像同卵双胞胎。由于亚洲狮的基因库很小,70%-80%的精子有缺陷,所以300头狮子听起来很多,但它们的前景并不乐观。需要说 明的是狮子处于食物链的最高端,1450平方公里的保护区养活不了300头狮子,最近的调查发现已经有40头狮子从保护区内溜了出来。

与 华南虎事件比较:镇坪县,人口不足7万,总面积1503平方公里,植被覆盖率82.4%,计划建设1000平方公里的自然生态保护区。对群众举报的华南虎 活动频繁的城关镇文彩村、曾家镇向阳村、上竹乡湘坪村、以及钟保镇青林村等四个地带,共150-200平方公里的范围实行特别保护地特别保护措施。从数字 猜测即便这150-200平方公里里面有几只老虎,野生华南虎的前景也不乐观,有时候人的愿望是美好的,但事实终究是事实。

参考:国家地理中文版 2001年 6月号

物理学在生物与医学中的重要应用

January 6th, 2008

译自The impact of physics on biology and medicine中的表格,总结得很全面。

物理学 生物医学
静力学 骨科
动力学 心脏运动
弹性力学 骨科
流体静力学 血压
流体动力学 循环系统
声学 听诊器,超声,超声成像
电磁学 所有生命过程
磁学 核磁共振成像
光与光学 光学显微镜、激光治疗、光纤
热学与热力学 热平衡(Heat balance)
分子运动论 布朗运动、渗透作用、扩散
原子物理与波谱学 NMR中化学位移、激光应用于医学
分子物理 遗传学、抗体、蛋白质结构、电子显微镜
紫外与红外 消毒、成像技术
X射线 放射医学、计算机断层扫描(computed tomograhy,CT)
量子力学 电子显微镜
相对论 同步辐射成像
晶体学 蛋白质结构
固体物理和半导体物理 计算机技术,闪烁成像(scintigraphy)
核物理 核医学、放射治疗、放射性同位素标记
放射性 正电子发射断层成像(Positron emission tomography,PET)
基本粒子物理 派介子疗法(Pion therapy)
加速器,回旋加速器 肿瘤治疗,霍奇金病(Hodgkin’s disease)
天文学及天体物理 发现氦,治疗哮喘(吸入氦-氧混合气体)

科学史上最漂亮的10个物理实验

January 6th, 2008

英国的物理网喜欢各种有趣的评选活动。比如他们曾在2002年评出了科学史上最漂亮的10个物理实验

  1. 单电子双缝干涉实验(Young’s double-slit experiment applied to the interference of single electrons)
  2. 伽利略的落体实验(Galileo’s experiment on falling bodies),1600s
  3. 密立根油滴实验(Millikan’s oil-drop experiment),1910s
  4. 牛顿三棱镜分光实验(Newton’s decomposition of sunlight with a prism),1665-1666
  5. 杨氏干涉实验(Young’s light-interference experiment),1801
  6. 卡文迪什扭摆实验测量万有引力常数(Cavendish’s torsion-bar experiment),1798
  7. 厄拉多塞测量地球的直径(Eratosthenes’ measurement of the Earth’s circumference),公元前三世纪
  8. 伽利略斜面实验(Galileo’s experiments with rolling balls down inclined planes),1600s
  9. 卢瑟福散射实验(Rutherford’s discovery of the nucleus),1911
  10. 傅科摆(Foucault’s pendulum),1851

未上榜的著名实验还有:

  • 阿基米德的王冠实验: Archimedes’ experiment on hydrostatics
  • 罗默测量光速实验:Roemer’s observations of the speed of light
  • 焦耳热功当量实验:Joule’s paddle-wheel heat experiments
  • 雷诺层流实验:Reynolds’s pipe flow experiment
  • 马赫声冲击波实验:Mach & Salcher’s acoustic shock wave
  • 迈克尔逊-莫雷实验:Michelson-Morley measurement of the null effect of the ether
  • 伦琴发现麦克斯韦位移电流:Röntgen’s detection of Maxwell’s displacement current
  • 奥斯特电磁感应实验:Oersted’s discovery of electromagnetism
  • 布拉格X-射线散射实验:The Braggs’ X-ray diffraction of salt crystals
  • 爱丁顿观测到星光被太阳偏转实验:Eddington’s measurement of the bending of starlight
  • 斯特恩-盖拉赫实验:Stern-Gerlach demonstration of space quantization
  • 薛定谔猫理想实验:Schrödinger’s cat thought experiment
  • Trinity test of nuclear chain reaction
  • 吴健雄验证宇称不守恒:Wu et al.’s measurement of parity violation
  • Goldhaber’s study of neutrino helicity
  • 费曼O圈实验:Feynman dipping an O-ring in water,费曼在挑战者号航天飞机失事调查委员会上把O形密封圈丢进冰水中证明低温可使橡胶变脆,由此解开了失事的谜团。

设想中的载人火星飞行

January 6th, 2008

1.从地球出发:火星基地由航天飞机衍生的巨型火箭发射。

01_marsbase.jpg
2.第一站:火星探险队的人员和设备在国际空间站短暂停留。

02_marsbase.jpg
3.奔向火星:将使用基于太阳能的电力推进。

03_marsbase.jpg
4.进入火星大气层。

04_marsbase.jpg
5.在火星着陆:将必要的人员和设备从飞船上卸下来。

05_marsbase.jpg
6.火星居住仓充气:供宇航员在火星上居住使用。

06_marsbase.jpg
7.宇航员建立火星科学考察站。

07_marsbase.jpg
8.宇航员使用钻探设备采集火星表面的土壤。

08_marsbase.jpg
9.宇航员进行火星极地探险。

09_marsbase.jpg
10.宇航员使用连接在笔记本电脑上的显微镜进行研究。

10_marsbase.jpg
11.宇航员采集并研究火星上的岩石,也许能找到火星生命的化石呢。

11_marsbase.jpg
12.火星探险队由多国宇航员组成。

12_marsbase.jpg
13.我们的火星基地。

13_marsbase.jpg
14.是回家的时候了。

14_marsbase.jpg
注:译自Space.com

什么是伪科学

January 6th, 2008

What is Pseudoscience?

伪科学一词最早出现在1843年,是由一个希腊词根 pseudo 和一个拉丁词根 scientia 组成。pseudo 对应英文为 false,scientia对应英文为 science。false,有虚伪,虚假,错误,捏造等含义;scientia 指知识或某一领域内的学问。pseudoscience 一词在使用时常含贬义,汉语一般译为伪科学。

关于伪科学(pseudoscience)一词的定义是有争议的,通常的定义是:

自称为科学,但又不遵循科学方法的知识或理论。

伪科学貌似科学,但无法用科学方法予以检验。在西方,骨相学(Phrenology),占星术(astrology)等被认为是典型的伪科学。

19世纪卡尔·波普尔提出可证伪性(falsifiability)是区分科学与非科学(包括伪科学)的标准。比如:

上帝创造了宇宙(God created the universe)。

就是不可证伪的,所以这样的知识属于非科学,它们在科学的领域之外。按照波普尔的可证伪原则:哲学、数学、神学、宗教等都不是科学。但波普尔并未给出非科学与伪科学的清楚划分。他列举星相学、精神分析为伪科学的代表,而爱因斯坦的相对论为科学的代表。

1978年,Paul Thagard 提出将那些在相当长时间内比其他竞争理论发展缓慢的理论区分出来,会有助于我们判定伪科学。原文:

Paul Thagard (1978) proposed that pseudoscience is primarily
distinguishable from science when it is less progressive than
alternative theories over a long period of time, and the
selective and or lack of attempts by proponents to solve
problems with the theory.

1984年,Mario Bunge 提出将“信仰领域”(belief fields)和“研究领域”区分开,会有助于我们判定伪科学。

科学哲学家保罗·费耶阿本德(Paul Feyerabend)认为,在社会科学领域,区分科学与非科学是不可能的,也是不必要的。而且在科学的某个领域内适用的判定(伪科学)标准未必适用于其他领域。Thagard (1978)从社会学的角度就伪科学问题讨论:

教育人们科学是如何地区别于伪科学是努力让公众不要漠视科学的哲学努力。

原文

elucidation of how science differs from pseudoscience is the
philosophical side of an attempt to overcome public neglect of
genuine science.

根据美国1988年关于公众科学知识的调查,50%的成年美国人反对进化论,88%的人认为占星术是科学。

伪科学标志小结

1. 含混,夸大或无法验证的断言(Use of vague, exaggerated or untestable claims)
2. 对理论超级自信(Over-reliance on confirmation rather than refutation)
3. 对其他专家的检验缺乏开放态度(Lack of openness to testing by other experts)
4. 缺乏进展(Lack of progress)
5. 过于个人化(Personalization of issues)

科 学也是区别于启示(revelation), 神学(theology), 或属灵的(spirituality)。如果不自称是科学的或与公认科学事实违背,使用启示的方法获得知识不被认为是伪科学。(注:这里的讨论与西方基督 教传统有关,托马斯·阿奎那认为信仰和理性是获得知识的两个可靠来源,但它们都只在各自领域内适用,不互相冲突,见:关于上帝“存在”的说明。托马斯·阿奎那是经院哲学的代表,罗马天主教会的官方哲学。)

伪科学与前科学

前 科学(protoscience)指的是科学建立之前所形成的理论,如化学的前身是炼金术,医学的前身是巫术等。费耶阿本德认为很难在科学,前科学,伪科 学之间进行区分。如前科学很容易与伪科学混淆,但前科学在科学发展的历史过程中是有价值的。(注:炼金术的基本理论或根本目的是:将贱金属变为贵金属。用 化学的概念看,这是错误的,但炼金术使用的基本方法,如使用天平对质量进行精确测量对导致化学的产生是极其关键的。)

科学与伪科学的分界问题

经过一个多世纪科学哲学家(或科学史家)与科学家在多个学科领域的对话,尽管大家对科学方法有很大程度上的认同,科学与伪科学的分界问题仍然是个有争议的问题。

很多被贴上伪科学标签的研究者及其理论的支持者质疑分界太过严厉,一些现在被接纳为科学的领域曾被认为是伪科学或具有伪科学的某些标志,如结果没有可重复性,缺少可证伪性。(注:维基百科中未给出参考文献。)

有些理论家认为实验验证本身并非一定是科学方法,科学史家托马斯·库恩认为在他的理论(范式理论)和卡尔·波普尔的理论中实验方法并不是决定性的因素。

原文can testing play a quite decisive role?

Daniel Rothbart 认为科学的重要标志并非实验的成功,很多真科学往往已经被实验否定。

原文

the defining feature of science does not seem to be experimental success, for most clear cases of genuine science have been experimentally falsified

这 是否意味着科学理论必须能够解释所有与其竞争的其他理论所无法解释的现象,在经验上与竞争理论相冲突并导致与竞争理论不一样的实验结果。这样一个理论是科 学的或非科学的就依赖于历史的环境。如果它比同时代的其他解释更好,就意味着科学进步。比如在古希腊,很多领域,如:迷信(superstition), 宗教(religion),魔法(magic)和神秘(the occult)被认为是正统的科学。这就是科学理论相互竞争的模型,Rothbart 认为这并不是一个完全有效的模型。(注:在古希腊,即便是苏格拉底这样死于渎神指控的哲学家,他认为自己是信神的。更具体一点,托勒密的地心说当时在预言 天文现象时要比日心说更有优越性。)

库恩认为相互竞争的范式(注:科学史家拉卡托斯称之为科学研究纲领。)之间的竞争很容易导致相互漫骂,他们会各自向公众寻求支持,而公众是缺乏判断竞争理论的能力的。科学哲学家 Larry Laudan 更认为伪科学一词并无科学意义,它大多时候描述了我们的情绪:

如果我们需要站出来并进行理性的讨论,我们会冒出伪科学或不科学这样的词汇,它们完全是空洞的说法并仅仅对我们的情绪有影响。

原文

“If we would stand up and be counted on the side of reason, we ought to drop terms like ‘pseudo-science’ and ‘unscientific’ from our vocabulary; they are just hollow phrases which do only emotive work for us”.

哈佛大学心理学教授 Richard McNally 认为:伪科学一词仅仅是在传媒争论中快速否定对方的煽动性的废话。

原文

“The term ‘pseudoscience’ has become little more than an inflammatory buzzword for quickly dismissing one’s opponents in media sound-bites”

科学共同体

库恩是当代最有影响力的科学史家,他从社会学的角度看待科学的问题,科学家是以共同方法、价值观(范式)组织起来的社会群体,科学共同体的工作(一般体现为科学期刊内的文章)是典型的科学工作。

曾经被认为是伪科学的科学

在科学史中我们甚至可以找到曾经被(科学共同体内)大多数学者认为是伪科学的理论后来又成为大家公认的理论,如:著名的大陆漂移学说。

科 学家有时会因为理论缺少可能的实验检测,而称该理论为伪科学,比如宇宙论就曾被认为是伪科学。(注:说到宇宙学,我立刻想到的是“针尖上能占多少个天使” 这样的中世纪哲学问题。)现在很热门的弦论(string theory)也因为同样的理由被一些物理学家批评。如:李·斯莫林(Lee Smolin)的The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next.一书。

参考阅读

  1. Answers: Pseudoscience
  2. Book Review: The Trouble with Physics