# Importance

.

When you give importance to people,
they think that
you are always free.

.

But
[what] they don’t understand [is] that
you [have to] make yourself available for them every time.

.

.

2013.09.19 Thursday ACHK

# 量子力學 1.11

『量子力學』一定正確

『量子決定論』一定正確

」，

」，

『量子力學』由發現至今八十多年；每逢應用在引力不強的物理系統時，都會得到準確的預測。所以「量子力學」本身，極度可信。

— Me@2013.09.19

# Logical implication 2

In this distinction, material implication is a symbol at the object level, while logical implication is a relation at the meta level. In other words, material implication is a function of the truth value of two sentences in one fixed model, but logical implication is not directly about the truth values of sentences in a particular model[. It] is about the relation between the truth values of the sentences when all models are considered.

There is a close relationship between the two notions in first-order logic. It is somewhat immediate from the definitions that if holds in every model then , and conversely if then is true in every model. This relationship becomes more fuzzy when we begin to look at other logics, and in particular it can be quite fuzzy when philosophers talk about material conditionals and logical implication independent of any formal system.[1]

— Mathematics – Stack Exchange

— Oct 1 ’11 at 2:52

— Carl Mummert

[1] should be replaced by  \phi \models \psi in LaTeX code.

2013.09.18 Wednesday ACHK

# Mother Nature

Sometimes, even Mother Nature is unkind.

— Me@2011.03.31

# Always make new mistakes, 7.1

（CYW：96 和 97。）

（CYW：我有時間就做多一點。）

（CYW：但是，一份連三個小時也霸佔不到。）

（TK：一份只消磨到一個多小時。）

（CYW：無錯無錯。）

（HYC：其實有很多課題還未教，所以有很多題目還未能動筆，唯有暫時跳過。）

（TK：短題目之中，其實我只做到其中兩題。）

（TK：沒有。）

— Me@2013.09.15

# Equivalence principle, 3

NumCracker

Dear Lubos, if one takes equivalence principle as really serious at microscopic level … what should be the quanta of “inertial forces”?

Lubos Motl

The equivalence principle says that inertia is *equivalent* to gravity, that’s why it’s called the “equivalence” principle.

So if you ever construct a description of inertial forces that uses virtual particles, it’s of course gravitons, the same particles as for gravitational forces, by the equivalence principle!

Your question therefore proves that you did *not* take the equivalence principle seriously yet.

NumCracker

Amazing! So the very existence of gravitons is a frame-dependent (non-covariant) concept … thanks for answering ;-)

— Confusions about the relationships of special relativity and general relativity

— Lubos Motl

2013.09.13 Friday ACHK

# Omnipotence 3

In psychology

Early Freudianism saw a feeling of omnipotence as intrinsic to early childhood. ‘As Freud and Ferenczi have shown, the child lives in a sort of megalomania for a long period…the “fiction of omnipotence”‘. At birth. ‘the baby is everything as far as he knows – “all powerful”…every step he takes towards establishing his own limits and boundaries will be painful because he’ll have to lose this original God-like feeling of omnipotence’.

— Wikipedia on Omnipotence

2013.09.13 Friday ACHK

」，

『經典物理學』是正確的

」，

— Me@2013.09.12

# Usability 2

One good way to evaluate the usability of a program or dialog is to… try to use the mouse with just one finger.

— Joel Spolsky

2013.09.12 Thursday ACHK

# A good speaker

Definition of a good speaker:

His overrunning does not annoy you.

— Me@2011.04.27

If you do not mind if a speaker overruns a speech, he must be a good speaker.

— Me@2013.09.12

# 如夢初醒 4.1

（CYM：我很夜才睡得著覺。）

「有心栽花花不香，無心插柳柳成蔭。」

「把手緊握 什麼都沒有  把手放開 你得到一切  — 臥虎藏龍」

（CYM：但是，有時一等就要等兩個多小時，沉悶非常。）

— Me@2013.09.11

# For all, 3.2

Omnipotence 2

.

Another problem of the concept “omnipotence” (all power) is that “all” must have a domain. Without a context, “all” is meaningless.

“All” does not mean “infinite”. Instead:

all

~ exhausted

~ nothing missing

— Me@2013-09-07 8:54 PM

.

Without a proper definition of “all”, mixing language levels is inevitable. Mixing levels could create self-reference, in turn could create logical contradictions.

A logical contradiction due to mixing different language levels is called a “paradox”.

A classic example is:

If X is omnipotent, X can create a stone that it cannot lift. Then X is not omnipotent, because there is a stone it cannot lift.

So omnipotence is a self-contradictory concept.

— Me@2020-04-06 09:58:46 PM

.

.

# Meaningful 13

e.g. 人生的意義 ~ 人生的下一步

life ~ keeps changing

death ~ stops changing

— Me@2013-09-08 12:17:56 PM

# 量子力學 1.9

「重言句」是詞語之間的關係。「重言句」的正確與否，你只要觀察句子之中，各個字詞的意思，就可以判斷得到，而毋須對外在世界，作任何形式的觀察或者實驗。所以，「重言句」的代價是，它沒有任何訊息內容。意思是，它對這個世界無所描述，導致你不能從它身上，去了解外在世界。例如，究竟冰箱內，有西瓜還是沒有西瓜呢？

— Me@2013.09.10

# The Illusion of Gravity, 2

We are also familiar with some curved spaces. Curvature comes in two forms, positive and negative. The simplest space with positive curvature is the surface of a sphere. A sphere has constant positive curvature. That is, it has the same degree of curvature at every location (unlike an egg, say, which has more curvature at the pointy end).

The simplest space with negative curvature is called hyperbolic space, which is deﬁned as space with constant negative curvature. This kind of space has long fascinated scientists and artists alike. Indeed, M. C. Escher produced several beautiful pictures of hyperbolic space …

— The Illusion of Gravity

— Juan Maldacena

2013.09.09 Monday ACHK

— 孫子兵法

Throw your soldiers into positions whence there is no escape, and they will prefer death to flight. If they will face death, there is nothing they may not achieve. Officers and men alike will put forth their uttermost strength.

Soldiers when in desperate straits lose the sense of fear. If there is no place of refuge, they will stand firm. If they are in hostile country, they will show a stubborn front. If there is no help for it, they will fight hard.

— The Art of War (Sun)/Section XI

When there is no choice, there is no uncertainty.

You do not have to use any brainpower to make any decisions.

So you take the actions directly.

— Me@2011.04.26

choice ~ uncertainty

fear ~ the feeling of uncertainty

no choice ~ no fear

— Me@2013.09.08

# Allow no exceptions 4

（HYC：做兩份呢？）

「Allow no exceptions」（不容有例外）的意思是，你安排了每星期做一份「Mathematics and Statistics」past paper 的話，就要做到一份，不少不多。「做多一份」和「做少一份」，同樣都是害己不淺，因為在這一科「做多了一份」，其實就相當於在另一科「做少了一份」，除非你有無限的時間。

1. 心情欠佳，提不起勁；

2. 書桌亂七八糟，似乎需要先行整理一下；

3. 電視劇大結局；

4. 男朋友打電話給你，要和你分手；

— Me@2013.09.06

— 改編自阿拉伯諺語

— Me@2013.09.06

# Black hole information paradox, 3

Among these insights that have convinced Hawking, you find Matrix theory and especially the AdS/CFT correspondence. Gravity in asymptotically AdS spaces has an equivalent description in terms of a conformal field theory living on its boundary. This conformal field theory is manifestly unitary and has no room for destruction of the information. This answers an equivalent question about gravity, too.

This brings most sane physicists to the opinion that the information is preserved and gravitational physics is not that special after all. But it does not give us a quantitative, calculable framework that would explain how does the information get out of the black holes and what do these subtle correlations that remember the initial state look like.

— Hawking and unitarity

— Lubos Motl

2013.09.05 Thursday ACHK

# Try something impossible

— 孔子

.

Sometimes you have to try something “impossible”, because you are looking for exceptions.

Even if you cannot find any existing exceptions, you may still be able to create some new ones, in case the opportunity cost is still acceptable.

— Me@2013-08-19 12:37:42 AM

.

.

— Me@2013.09.04