Quantum coherence
The quantum description of perfectly coherent paths is called a pure state, in which the two paths are combined in a superposition. The correlation between the two particles exceeds what would be predicted for classical correlation alone (see Bell’s inequalities).
— Wikipedia on Quantum coherence
2011.09.30 Friday ACHK
誰終將聲震人間，必長久深自緘默；誰終將點燃閃電，必長久如雲漂泊。
— 尼采
Teaching is not filling a vase, but lighting a fire.
— Michel de Montaigne
Teaching is not filling a vase, but lightning a fire.
— Me@2005
教師任務 點石成金
— Me@2007.08.21
燭燃閃電 點石成金
— Me@2010.11.28
2011.09.30 Friday (c) All rights reserved by ACHK
Probability
Always make new mistakes, 6
這段改編自 2010 年 5 月 18 日的對話。
（HYC: Probability（機會率）的題目要麼就是全題對，要麼就是全題錯，令人惶恐非常。）
Probability 的題目，我自己也很驚。我暫時也沒有辦法，保證自己運算正確。那樣，你可以做些什麼，來提高準繩度呢？
你在平日做 probability 題目時，把所有犯過的錯誤，和對應的解答，都一一儲存在「魔法筆記」中。然後，你在每次做練習題目前、考試前一天 和 臨考試前的半小時，都把「魔法筆記」背誦一次。透過這個形式的反覆背誦，你就可以「免疫」：考試時，你不會再犯平日犯過的錯誤。
從這個角度看，平日犯的錯誤越多，考試的分數反而會越高。在平日沒有犯過的錯誤，你在考試就有機會錯；在平日有犯過的錯誤，你在考試就沒有機會錯，因為你已經事先「注射」了「疫苗」。
Probability 的題目最驚嚇的地方是，它們貌似幾乎沒有任何步驟。錯了一題後，想知自己在哪一步的思考有漏洞，對初學者來說，是一個不可能的任務。
「貌似沒有步驟」所衍生的另一個大問題是，在考試途中，你不知如何驗算。
（這兩個問題，我在去年破解了。 — Me@2011.09.29）
— Me@2011.09.29
2011.09.29 Thursday (c) All rights reserved by ACHK
Quantum coherence, 1
Berthold-Georg Englert, Marlan O. Scully & Herbert Walther, Quantum Optical Tests of Complementarity, Nature, Vol 351, pp 111–116 (9 May 1991) and (same authors) The Duality in Matter and Light Scientific American, pg 56–61, (December 1994). Demonstrates that complementarity is enforced, and quantum interference effects destroyed, by decoherence (irreversible object-apparatus correlations), and not, as was previously popularly believed, by Heisenberg’s uncertainty principle itself.
— Wikipedia on Complementarity (physics)
2011.09.28 Wednesday ACHK
If your life gets better and better, you will not miss the past.
時常緬懷過去，代表你的生活情況越來越差。
— Me@2011.09.25
2011.09.28 Wednesday (c) All rights reserved by ACHK
這段改編自 2010 年 3 月 6 日的對話。
對話比演講或者寫作容易得多，因為對話時，你只需要考慮第一句說什麼，然後根據對方的反應，就自動知道第二句應該說什麼。除了第一句之外，你幾乎毋須作任何的盤算。
只要把自己和別人的對話錄音，然後把那些錄音改編成文章。就可以完全避免了「缺乏寫作靈感」的問題。
— Me@2011.09.27
… if you can’t get started, tell someone what you plan to write about, then write down what you said …
— Writing, Briefly
— Paul Graham
2011.09.27 Tuesday (c) All rights reserved by ACHK
The broad notion is that “mass there influences inertia here”.
— Wikipedia on Mach principle
Mach principle states that the inertial mass of an object is due to (the gravitational influences of) other objects.
In other words, the inertial mass of an object is due to the gravitational mass of itself and the gravitational masses of other objects.
— Me@2011.09.24
2011.09.27 Tuesday (c) All rights reserved by ACHK
change = delete the old one + create a new one
— Me@2010.11.28
2011.09.26 Monday (c) All rights reserved by ACHK
年年齡 9
2004 年，我參加碩士畢業禮時，
大學副校長會同畢業生逐一握手和合照留念。
我和他握了手，我就立刻「擺 pose」（擺姿勢／作態）。當我剛剛「擺 pose」，開始對著攝影機鏡頭微笑之際，
攝影師就說：「下一位。」
人生就是那樣：當你企圖「擺 pose」時，就已經是「下一位」。
— Me@2007
2011.09.26 Monday (c) All rights reserved by ACHK
“A purpose of life” is to locally decrease the entropy
which is pretty unusual among the natural phenomena.
— Ten new things modern physics has learned about time
— Lubos Motl
2011.09.25 Sunday ACHK
His burning passion was to help the world stop wasting his time.
— I’m Feeling Lucky, p. xiii
— Douglas Edwards
2011.09.25 Sunday ACHK
即使在假日，如果有四個小時可以集中到精神，去做需要高度思考的工作，就已經十分難得。
就算是專業的數學家，有些每天最多只可以用四個小時去研究數學。[1] 其餘時間則用來處理其他事務性質工作，例如教學。
— Me@2011.09.24
[1] I Want to Be a Mathematician, by Paul R. Halmos
2011.09.24 Saturday (c) All rights reserved by ACHK
AdS/CFT correspondence 4
AdS/CFT is a unification of field theory and string theory – a kind of spectacular meta-unification, too.
— Unification as a source of certainty
— Lubos Motl
2011.09.24 Saturday ACHK
Have you ever stood and stared at it, marveled at its beauty, its genius? Billions of people just living out their lives, oblivious. Did you know that the first Matrix was designed to be a perfect human world, where none suffered, where everyone would be happy? It was a disaster. No one would accept the program, entire crops were lost. Some believed we lacked the programming language to describe your perfect world, but I believe that, as a species, human beings define their reality through misery and suffering. The perfect world was a dream that your primitive cerebrum kept trying to wake up from. Which is why the Matrix was redesigned to this, the peak of your civilization. I say your civilization, because as soon as we started thinking for you it really became our civilization, which is of course what this is all about. Evolution, Morpheus, evolution. Like the dinosaur. Look out that window. You had your time. The future is our world, Morpheus. The future is our time.
— Agent Smith
— The Matrix
2011.09.24 Saturday ACHK
唔識就飛（完全版）1.4
這段改編自 2010 年 5 月 18 日的對話。
當年，如果我不是嚴格執行這個「唔識就飛」政策的話，你現在就見不到我。
我在 純數學科 的高考時，七題 Section A 的題目之中，竟然有四題不懂做。那是非常驚嚇的事情，因為 Section A 的都是較短較淺的題目，而我卻有超過一半不懂做。我在平日練習時，通常也不會那麼差，偏偏在真正考試的那一次，有出人意表的劇情。如果發生在你身上，你會有什麼感受？
幸好，我在平日的練習中，已習慣了「唔識就飛」：想不通的話，就立刻先做下一題，或者同一題的下一部分。在原定的時間編排中，我應該花一小時在 Section A 和兩小時在 Section B。但是，因為有四題不懂的緣故，我在 35 分鐘左右就「完成」了 Section A，立刻跳去做 Section B。那樣，我就「儲存」了一些時間。完成 Section B 後，我還剩下 25 分鐘，去處理 Section A。
結果，那四題都給我想通了。
如果我不是平時訓練有素，我就不會有那樣的心理素質，去嚴格執行「唔識就飛」。執行不到「唔識就飛」，我就會在考試中浪費很多時間，導致我 純數學科 不合格，繼而入不到大學。入不到大學，我就不會是老師，你就不會在現在見到我。
— Me@2011.09.23
2011.09.23 Friday (c) All rights reserved by ACHK
In fact, all the dualities in string theory are obviously examples of unification. The electric charge is unified with the momentum of a particle; this insight was already known to Kaluza or at least Klein. That’s true because the electric charge is the generator of an isometry in a new 5th circular dimension – which is the momentum in this direction.
— Unification as a source of certainty
— Lubos Motl
2011.09.22 Thursday ACHK
Software in small becomes hardware in big:
Part of your intelligence hardware
is your intelligence software installed when you were small.
— Me@2011.09.21
.
.
2011.09.21 Wednesday (c) All rights reserved by ACHK
上班 8 | 自然定律 1.2
這段改編自 2010 年 3 月 6 日的對話。
（安：你講過，Stephen Covey 的講法，通常也不會不切實際。你所舉的例子是，有一個讀者問他：「我想開一間咖啡館，哪我好不好辭去我的工作呢？」Stephen Covey 回答：「不要。先留住你現時的職位。執行你的理想往往比你想像中困難。所花的時間亦會比你想像中長。最好是先留住你現時的工作，然後用工餘的時間經營咖啡館的事務。〔如果你在咖啡館成功前就辭去現時的工作的話，你很可能沒有足夠金錢維生。〕」
「留住現時的工作，然後用工餘的時間經營自己的理想」我覺得十分合理，適合絕大多數人。但是，執行起來，我遇到一個實際的困難，就是 …）
沒有工餘時間？
（安：不是。我有工餘時間。而且，我的工餘時間，比一般受僱人士為多。但是，我在工餘時間的精神很差，集中不到心智去實行自己的理想，例如閱讀。
而我又覺得，每天一早去上班，其實就等於將自己最有精神的時段，去做一大堆近乎毋須任何思考的事務性質工作，十分可惜。）
其實，不只是上班，在讀書時代，也會遇到同樣的問題。大學時期，日間要上課和參加課外活動等，晚上回家後，即使有時間，也已經沒有精神去做功課和溫習。
我當時的解決方法是，回家後立刻睡覺，早上起來才工作。我有時會在晚上九時半睡覺，然後在凌晨三時半起來讀書。有時則會在十時半睡覺，四時起來。一般來說，我可以工作至七時半。平均而言，我每天也有三至四個小時高度集中的時間。
後來，我才發現，有不少人也用這個方法。例如，數學家陳省身每天也是凌晨起來研究數學，而日間則用來處理一些事務性質工作。
— Me@2011.09.21
2011.09.21 Wednesday (c) All rights reserved by ACHK
My high school teachers in mathematics were excellent. We studied rather advanced topics in mathematics. I had no difficulty with them.
However, I was rather disappointed that my physics teacher was not good enough. The fundamental intuition in physics was not established during my high school year. I regretted it up to now.
— Shing-Tung Yau
2011.09.19 Monday (c) All rights reserved by ACHK
緣份 4
Life is a lot of problems.
You are the solutions.
— Me@2011.09.19
2011.09.19 Monday (c) All rights reserved by ACHK
Physics Town 
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