diff 3b
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Mostly it is loss which teaches us about the worth of things.
— Arthur Schopenhauer
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Anything that does not change you cannot see, because it falls into the background.
你不會到留意「正常」的事物，因為，它們會化成「背景」。
— Me@2011.04.22
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想知一件事物的價值，你先要嘗試失去它。
你不會到留意「正常」的事物，因為腦部毋須處理「正常」的事物，所以會自動忽略它們，以節省資源去解決「問題」。（「問題」就是不如意的事物。）
— Me@2011.04.24
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2011.04.24 Sunday (c) All rights reserved by ACHK
A physical object is observable if and only if it breaks a symmetry.
— Professor Renbao Liu
2011.04.23 Saturday ACHK
網誌時代 10
我發覺我和學生的對話中，來來去去都是回答同一堆的問題，例如：
「我快要考試，但來不及溫習。我應該怎麼辦呢？」
「我溫習了的東西，幾日之後就忘記了。」
「我那天用了兩個小時，研究一題數學題目，結果其他東西沒有足夠時間去完成。」
「昨天是假期，我原本打算早上九時起來溫習。但是，我睡到十一時才醒，斷送了兩個小時，令我內疚非常。結果，我花了整天的時間去內疚，不能專心溫習。」
人所遇到的問題，有一部分是共通的，而又不斷重複。
— Me@2011.04.23
2011.04.23 Saturday (c) All rights reserved by ACHK
By abstracting away the very concept of looping, you can implement looping any way you want, including implementing it in a way that scales nicely with extra hardware.
Without understanding functional programming, you can’t invent MapReduce, the algorithm that makes Google so massively scalable. The terms Map and Reduce come from Lisp and functional programming. MapReduce is, in retrospect, obvious to anyone who remembers from their 6.001-equivalent programming class that purely functional programs have no side effects and are thus trivially parallelizable.
The very fact that Google invented MapReduce, and Microsoft didn’t, says something about why Microsoft is still playing catch up trying to get basic search features to work, while Google has moved on to the next problem: building Skynet^H^H^H^H^H^H the world’s largest massively parallel supercomputer. I don’t think Microsoft completely understands just how far behind they are on that wave.
— Can Your Programming Language Do This?
— Joel Spolsky
2011.04.22 Friday ACHK
complete set 知識完備集合
= critical mass of knowledge
— Me@2010.11.17
2011.04.21 Thursday (c) All rights reserved by ACHK
一步 1.2
這段改篇自 2010 年 5 月 1 日的對話。
所以，你做任何一部分時，應該用紙遮蓋著之後的部分，讓自己看不到它們，直到你完成眼前的部分為止。那樣，一方面，你不會被之後的部分所分心。另一方面，你的心理負擔會輕盈了一些。
試想想，當你正在做 a 部分，萬一不慎看到 b 部分，而又發覺不是立刻懂做的話，你的心裡就會產生不必要的不安，從而減低你做到 a 部分的機會。
（CKY：這個技巧，好像是在催眠著自己。）
不要輕視這些小動作的重要性。考試有很大部分，是在鬥心理狀態管理。心理狀態管理得好，勝算會大很多。
— Me@2011.04.21
2011.04.21 Thursday (c) All rights reserved by ACHK
The importance of gauge theories for physics stems from the tremendous success of the mathematical formalism in providing a unified framework to describe the quantum field theories of electromagnetism, the weak force and the strong force. This theory, known as the Standard Model, accurately describes experimental predictions regarding three of the four fundamental forces of nature, and is a gauge theory with the gauge group SU(3) × SU(2) × U(1). Modern theories like string theory, as well as some formulations of general relativity, are, in one way or another, gauge theories.
— Wikipedia on Gauge theory
2011.04.18 Monday ACHK
You can spend your whole life trying to be popular, but at the end of the day, the size of the crowd at your funeral will be largely dictated by the weather.
— Frank Skinner
你可以花一生的時間，令到自己受歡迎；但是，你的喪禮將會有多少人出席，還要視乎當日的天氣。
— Me@2010.07.16
2011.04.18 Monday (c) All rights reserved by ACHK
網誌時代 9.3
（安：回想以前，我們的對話內容之中，其實有很多也值得化成文字。幾年前的對話，我們沒有錄音，沒有紀錄下來，真的有一點點可惜。）
可惜的程度不大。重點是，你我還健在。真正重要的內容，在往後的對話中，自然會重新出現。不會重新出現的，即是無關痛癢。
— Me@2011.04.17
2011.04.17 Sunday (c) All rights reserved by ACHK
In mathematics and physics, a soliton is a self-reinforcing solitary wave (a wave packet or pulse) that maintains its shape while it travels at constant speed. Solitons are caused by a cancellation of nonlinear and dispersive effects in the medium.
Dispersion and non-linearity can interact to produce permanent and localized wave forms. Consider a pulse of light traveling in glass. This pulse can be thought of as consisting of light of several different frequencies. Since glass shows dispersion, these different frequencies will travel at different speeds and the shape of the pulse will therefore change over time. However, there is also the non-linear Kerr effect: the refractive index of a material at a given frequency depends on the light’s amplitude or strength. If the pulse has just the right shape, the Kerr effect will exactly cancel the dispersion effect, and the pulse’s shape won’t change over time: a soliton.
— Wikipedia on Soliton
2011.04.17 Sunday ACHK
No one cares what operating system you run as long as it stays up.
— Bruce Perens
That’s why the best choice of software is often no software — and barring that, as little software as you can possibly get away with, and even then, only from the most reputable and reliable sources.
— Coding Horror
— by Jeff Atwood
The greatest of rulers hardly dwells upon the minds of his subjects,
Lesser than this they forever draw near and laud him with great praise,
Lesser than this the people are held in his frightening awe and fear,
Lesser than this the people revile and curse him.
太上，下知有之；
其次，親而譽之；
其次畏之；
其次侮之。
— Laozi (Wikisource translation)
2011.04.16 Saturday ACHK
這段改篇自 2010 年 5 月 1 日的對話。
有很多類型的題目，驗算不會花太多時間，所以我建議你做完每一題後，就立刻驗算。驗算以後，發覺正確的話，你以後就毋須再看那一題，心理壓力會小了一點。
要減輕心理包袱的話，另外還有一個考試技巧。做任何一題時，不要讓自己看到下一題的東西，因為下一題的資料一定對你正在做的那一題沒有幫助。還有，做某一題的某一部分時，不要讓自己看到下一部分的東西。
上次提過，為什麼 section B（乙部）的每一題，都要分 a, b, c, d 四部分呢？
那是因為 section B 都是比較深的題目。如果一開始就問你 d 部分的話，大部分人都不會做到。倒轉來說，a, b 部分的舖排，其實是給考生的提示。由於是提示，所以會比較簡單容易，不會比 section A 的短題目深。
但是，不會有情況，要你運用 b 部分的結果，來做 a 部分。又不會有情況，要你運用 c 部分的結果，來做 b 部分。既然之後的部分，對你沒有任何幫助，那就不應該理會它。反而，你應該專心思考你當時的部分。
所以，你做任何一部分時，應該用紙遮蓋著之後的部分，讓自己看不到它們，直到你完成眼前的部分為止。那樣，一方面，你不會被之後的部分所分心。另一方面，你的心理負擔會輕盈了一些。
試想想，當你正在做 a 部分，萬一不慎看到 b 部分，而又發覺不是立刻懂做的話，你的心裡就會產生不必要的不安，從而減低你做到 a 部分的機會。
— Me@2011.04.16
2011.04.16 Saturday (c) All rights reserved by ACHK
In chemistry, a catalyst is any substance that increases the rate of a desired chemical reaction without itself being consumed.
— Hacking Matter, p.159
2011.04.14 Thursday ACHK
We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct.
Said to Wolfgang Pauli after his presentation of Heisenberg’s and Pauli’s nonlinear field theory of elementary particles, at Columbia University (1958), as quoted in Symposium on Basic Research (1959) by Dael Lee Wolfle, p. 66
Your theory is crazy, but it’s not crazy enough to be true.
— Niels Bohr
2011.04.14 Thursday ACHK
網誌時代 9.2 | 種子意念 6.2
在寫網誌時，我的心態是，重點不是要分毫不差地紀錄原文，而是透過你我的對話，帶動我的寫作靈感。
我和你的「心靈作業系統」（思考模式）有相似的地方，所以，有時即使是較為深刻抽象的內容，都可以用很精簡的對話來描述。不好處是，其他的大部分人，因為和我們的思考背景不同，如果我把「原聲」輯錄成文字的話，他們不會明白，我們究竟在說什麼。
（安：無錯。我們對話時，不自覺地省略了很多我們的共同背景知識。你把那些背景知識都寫出來，令到一般的平民百姓都能夠明白。這一點本身就很 amazing。）
這就解釋了為何一天的錄音聲帶，我要花兩個月時間去整理加工，如果我一天寫一篇文章的話。
— Me@2011.04.13
2011.04.13 Wednesday (c) All rights reserved by ACHK
Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems.
“Atomic Physics and the Description of Nature” (1934)
— Niels Bohr
2011.04.13 Wednesday ACHK
If you are not lost, you are not a leader.
You are not lost only if you have someone else to follow.
— Me@2010.11.14
沒有不迷惘的領袖；
不感到迷惘的，就不叫做領袖。
— Me@2010.11.14
2011.04.12 Tuesday (c) All rights reserved by ACHK
這段改篇自 2010 年 5 月 1 日的對話。
「微積分」的概念，可能會比其他課題抽象，因為牽涉到「無限大」和「無限小」。但是，「微積分」的運算，說穿了，只是一大堆公式的背誦，不是什麼抽象的思考。你可以把學習「微積分」，看成學習一個「高級乘數表」的過程。
你在計算乘數時，並不會有什麼抽象的思維。你所做的，只是把乘數表背出來。所以，平時我說「我懂做乘數」並不是指，我對「乘數」有什麼深刻的了解。「我懂做乘數」的意思是，我背誦了「乘數表」，而且純熟到它已變成了我的自然反應。
（再者，想要對「乘數」的意思有深刻的了解，並不是那麼簡單容易。例如，5 x 2 = 5 + 5 ； 5 x 3 = 5 + 5 + 5。那樣，「5 x 2.1」究竟是什麼意思呢？）
同理，想要「微積分」的運算做得好，並不是要花大量時間，做抽象的思考，去了解「微積分」背後的終極真相。反而，你真正需要做的，只是把「微分（公式）表」和「積分表」背誦好，再加大量的練習，令到它們變成了你的條件反射。
— Me@2011.04.12
In mathematics you don’t understand things. You just get used to them.
— John Von Neumann
2011.04.12 Tuesday (c) All rights reserved by ACHK
People strongly tend to think probability is evenly distributed across as many unknowns as are present, whether it is or not (Fox and Levav, 2004:637).
— Wikipedia on Monty Hall problem
2011.04.11 Monday ACHK
Today you are you,
that is truer than true.
There is no one alive
who is youer than you.
— Dr. Seuss
2011.04.11 Monday ACHK
Physics Town 
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