# 眾害取其輕 10.1

The least of all evils, 10 | 地獄之路 3.2 | Good intentions 3.2

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1. 有問題一定要解決。

2. 「難受」一定要避免。

3. 任何情況下，都要避免自己或他人的難受。

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「眾害之最輕」有時可以零，有時不可以零。你只能客觀面對，不能主觀判斷。換句話說，「眾害之最輕」不一定「可以零」，亦不一定「不可以零」。

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1. 理解後背誦

2. 有用的東西就背

3. 無用的東西就不背

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— Me@2022.09.24 10:56:23 AM

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# 烹飪事實

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「善意謊言」的最大問題是，「善意」不代表「善行」，更不代表「善果」。到病人最終知道真相時，只加倍傷心。

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「我明日下午見，一位異性老朋友。你一同去嗎？」

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— Me@2022-06-12 01:08:49 PM

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# Dynamical pictures

Comparison of pictures

The Heisenberg picture is closest to classical Hamiltonian mechanics (for example, the commutators appearing in the above equations directly correspond to classical Poisson brackets). The Schrödinger picture, the preferred formulation in introductory texts, is easy to visualize in terms of Hilbert space rotations of state vectors, although it lacks natural generalization to Lorentz invariant systems. The Dirac picture is most useful in nonstationary and covariant perturbation theory, so it is suited to quantum field theory and many-body physics.

Summary comparison of evolutions

— Wikipedia on Dynamical pictures

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2022.04.05 Tuesday ACHK

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superposition

~ lack of the existence of measuring device in the definition of the experimental setup to define the difference between microscopic events in terms of the difference between observable physical events

— Me@2022-01-31 08:33:01 AM

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Note that superposition is mathematical, not physical. A wave function is not probabilities, nor a physical wave. Superposition applies only to wave functions, not to probabilities, nor to physical realities.

If superposition had been of probabilities or of physical realities, there would have been no interference patterns in the double-slit experiment.

— Me@2022-02-11 03:32:47 PM

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For example, in the double-slit experiment, if no detector is installed, the system is in a quantum superposition state.

It is not that each individual photon is in a superposition, because an individual particle has no 100% objective identity, due to the indistinguishability of identical particles. Instead, it is that the system of the whole experimental setup is in a superposition.

This applies also to other more complicated experimental setups, such the EPR experiment, the delayed-choice experiment, the delayed-choice quantum eraser, etc.

— Me@2021-01-23 12:57 AM

— Me@2022-02-11 03:29 PM

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physical definition

~ define the microscopic events in terms of observable physical phenomena such as the change of readings of the measuring device

~ define unobservable events in terms of observable events

— Me@2022-01-31 08:33:01 AM

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a definite state

~ an eigenstate

~ a state that has given a physical definition

— Me@2022-02-11 01:19:57 PM

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What we do in the present does not change the past, but changes we can see/say about the past. — Wheeler on Delayed choice quantum eraser, paraphrased, Me@2018-02-04 03:40:27 PM

Physics should deduce what an observer would observe, not what it really is, for that would be impossible. — Me@2018-02-02 12:15:38 AM

It is because, tautologically, any state that cannot be physically defined is logically and physically meaningless.

In other words, any state that has no distinguishing observable effects does not make sense. For example, if in a double-slit experiment, no detector is allowed, then it is no point to label the state either as “go-left” or as “go-right”. Instead, we have to label the state as a superposition state.

Some unobservable (aka microscopic) variables are meaningless. It is not because of any philosophical points of view, but because we have not defined those variables in terms of observables or observable events, aka physical phenomena. In other words, those variables have no physical definitions yet.

— Me@2022-02-11 03:50:59 PM

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Quantum mechanics, and physics in general, gives the rules of storytelling about reality. A story is a post hoc description of a physical event. In other words, quantum mechanics, and physics in general, is about phenomena, not noumena.

phenomenon (plural phenomena)

~ thing appearing to view

~ reality with respect to an observer

noumenon (plural noumena)

~ thing-in-itself

~ reality independent of any observers

— Me@2022-02-11 3:00 PM

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# Spinoza 3.2

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Intellect is invisible to those have none.

— Arthur Schopenhauer

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A stupid man’s report of what a clever man says is never accurate, because he unconsciously translates what he hears into something that he can understand.

— p.83

— Chapter XI. Socrates

— A History of Western Philosophy (1945)

— Bertrand Russell

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（安：根據羅素的講法，有很多人學習深奧學問時，所謂的「明白」，未必是真正的明白，因為他們會不自覺地，把那些新知識，翻譯成自己明白的版本；即是夾硬用，舊知識的語言，以理解新知識。Paul Graham 說在小時候，曾經用這個方法，去學習數學；即是將數學概念，翻譯成日常生活的概念。）

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（安：我記得是。當然，我可以記錯。但是，有沒有講過，或者誰講過，並不是重點。重要的是，那些講法，有沒有道理。

Everything which exists, exists either in itself or in something else.

That which cannot be conceived through anything else must be conceived through itself.

— Baruch Spinoza

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— Me@2022-02-03 12:09:36 PM

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# A Whole New World

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Do not ask your children to strive for extraordinary lives. Such striving may seem admirable, but it is the way of foolishness. Help them instead to find the wonder and the marvel of an ordinary life. Show them the joy of tasting tomatoes, apples and pears. Show them how to cry when pets and people die. Show them the infinite pleasure in the touch of a hand. And make the ordinary come alive for them. The extraordinary will take care of itself.

— William Martin

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I can show you the world
Shining, shimmering, splendid
Tell me, princess, now when did
You last let your heart decide?

Take you wonder by wonder
Over, sideways and under
On a magic carpet ride

A whole new world
A new fantastic point of view
No one to tell us, “No”
Or where to go
Or say we’re only dreaming

— Aladdin’s A Whole New World

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2022.01.24 Monday ACHK

# 超時空接觸 3

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— Me@2022-01-23 11:34:20 PM

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— Ludwig Wittgenstein

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— Me@2009.09.16

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# Logical arrow of time, 6.4.2

Logical arrow of time, 6.1.2

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The source of the macroscopic time asymmetry, aka the second law of thermodynamics, is the difference between prediction and retrodiction.

In a prediction, the deduction direction is the same as the physical/observer time direction.

In a retrodiction, the deduction direction is opposite to the physical/observer time direction.

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— guess —

If a retrodiction is done by a time-opposite observer, he will see the entropy increasing. For him, he is really making a prediction.

— guess —

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— Me@2013-10-25 3:33 AM

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A difference between deduction and observation is that in observation, the probability is updated in real time.

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each update time interval ~ infinitesimal

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In other words, when you observe a system, you get new information about that system in real time.

Since you gain new knowledge of the system in real time, the probability assigned to that system is also updated in real time.

— Me@2020-10-13 11:27:59 AM

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# 大腦物理性損毀不是比喻

99.85%的人不會，終身被匪欺騙教育，大腦已經物理性損毀了，假如說匪的謊言灌輸有20層，那麼絕大多數人遭鐵拳之後的反思，最多只能突破一兩層，達到“我愛國所以要說話”的程度，離理解台人港人藏人維人還非常遠，至少還需要十幾個層次的突破。所以覺醒者極少極少，而且沒有力量。很悲哀，但事實如此。

— 李穎

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People do not change. They die, replaced by other people.

Most people do not change. They die, replaced by a new generation of people.

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You cannot change the people around you, but you can change the people you choose to be around.

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2020.02.15 Saturday ACHK

# 少補習

— Me@2017-11-09 01:26:59 PM

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# 無限旅程 3.2

The main use of doing academic works is to enlarge your personal world.

Just like travel: travel in itself is useless, unless you are going to live there.

— Me@2011.10.11

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… or the travel experience travels with you.

— Me@2019-09-15 10:53:15 PM

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# Logical arrow of time, 7

When we imagine that we know and keep track of all the exact information about the physical system – which, in practice, we can only do for small microscopic physical systems – the microscopic laws are time-reversal-symmetric (or at least CPT-symmetric) and we don’t see any arrow. There is a one-to-one unitary map between the states at times “t1” and “t2” and it doesn’t matter which of them is the past and which of them is the future.

A problem is that with this microscopic description where everything is exact, no thermodynamic concepts such as the entropy “emerge” at all. You might say that the entropy is zero if the pure state is exactly known all the time – at any rate, a definition of the entropy that would make it identically zero would be completely useless, too. By “entropy”, I never mean a quantity that is allowed to be zero for macroscopic systems at room temperature.

But whenever we deal with incomplete information, this one-to-one map inevitably disappears and the simple rules break down. Macroscopic laws of physics are irreversible. If friction brings your car to a halt and you wait for days, you won’t be able to say when the car stopped. The information disappears: it dissipates.

— The arrow of time: understood for 100 years

— Lubos Motl

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If there is a god-view, there is no time arrow.

Time arrow only exists from a macroscopic point of view. Microscopically, there is no time arrow.

If there is a god-view that can observe all the pieces of the exact information, including the microscopic ones, there is no time arrow.

Also, if there is a god-view, there will be paradoxes, such as the black hole information paradox.

Black hole complementarity is a conjectured solution to the black hole information paradox, proposed by Leonard Susskind, Larus Thorlacius, and Gerard ‘t Hooft.

Leonard Susskind proposed a radical resolution to this problem by claiming that the information is both reflected at the event horizon and passes through the event horizon and cannot escape, with the catch being no observer can confirm both stories simultaneously.

— Wikipedia on Black hole complementarity

The spirit of black hole complementarity is that there is no god-view. Instead, physics is always about what an observer can observe.

— Me@2018-06-21 01:09:05 PM

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# Logical arrow of time, 6.4

The source of the macroscopic time asymmetry, aka the second law of thermodynamics, is the difference of prediction and retrodiction.

In a prediction, the deduction direction is the same as the physical/observer time direction.

In a retrodiction, the deduction direction is opposite to the physical/observer time direction.

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— guess —

If a retrodiction is done by a time-opposite observer, he will see the entropy increasing. For him, he is really doing a prediction.

— guess —

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— Me@2013-10-25 3:33 AM

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The existence of the so-called “the paradox of the arrow of time” is fundamentally due to the fact that some people insist that physics is about an observer-independent objective truth of reality.

However, it is not the case. Physics is not about “objective” reality.  Instead, physics is always about what an observer would observe.

— Lubos Motl

— paraphrased

— Me@2019-01-19 10:25:15 PM

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# 宇宙大戰 1.2

PhD, 2.4 | 故事連線 1.1.6 | 碩士 3.4

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（問：我也遇過類似的情境。

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（問：那樣，如果要「複雜地說」呢？）

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— Me@2019-01-01 11:20:57 PM

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# 宇宙大戰 1.1

PhD, 2.3 | 故事連線 1.1.5 | 碩士 3.3

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（問：你好似講到，人類那麼危險？）

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（問：人類真的那麼危險嗎？）

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（問：我也遇過類似的情境。

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（問：那樣，如果要「複雜地說」呢？）

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— Me@2018-12-20 11:06:49 PM

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# Relational quantum mechanics

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Relational quantum mechanics (RQM) is an interpretation of quantum mechanics which treats the state of a quantum system as being observer-dependent, that is, the state is the relation between the observer and the system. This interpretation was first delineated by Carlo Rovelli in a 1994 preprint, and has since been expanded upon by a number of theorists. It is inspired by the key idea behind special relativity, that the details of an observation depend on the reference frame of the observer, and uses some ideas from Wheeler on quantum information.

,,,

Relational solution

In RQM, an interaction between a system and an observer is necessary for the system to have clearly defined properties relative to that observer. Since the two measurement events take place at spacelike separation, they do not lie in the intersection of Alice’s and Bob’s light cones. Indeed, there is no observer who can instantaneously measure both electrons’ spin.

The key to the RQM analysis is to remember that the results obtained on each “wing” of the experiment only become determinate for a given observer once that observer has interacted with the other observer involved. As far as Alice is concerned, the specific results obtained on Bob’s wing of the experiment are indeterminate for her, although she will know that Bob has a definite result. In order to find out what result Bob has, she has to interact with him at some time ${\displaystyle t_{3}}$ in their future light cones, through ordinary classical information channels.

The question then becomes one of whether the expected correlations in results will appear: will the two particles behave in accordance with the laws of quantum mechanics? Let us denote by ${\displaystyle M_{A}(\alpha )}$ the idea that the observer ${\displaystyle A}$ (Alice) measures the state of the system ${\displaystyle \alpha}$ (Alice’s particle).

So, at time ${\displaystyle t_{2}}$, Alice knows the value of ${\displaystyle M_{A}(\alpha )}$: the spin of her particle, relative to herself. But, since the particles are in a singlet state, she knows that

${\displaystyle M_{A}(\alpha )+M_{A}(\beta )=0,}$

and so if she measures her particle’s spin to be ${\displaystyle \sigma }$, she can predict that Bob’s particle ( ${\displaystyle \beta }$ ) will have spin ${\displaystyle -\sigma }$. All this follows from standard quantum mechanics, and there is no “spooky action at a distance” yet. From the “coherence-operator” discussed above, Alice also knows that if at ${\displaystyle t_{3}}$ she measures Bob’s particle and then measures Bob (that is asks him what result he got) — or vice versa — the results will be consistent:

${\displaystyle M_{A}(B)=M_{A}(\beta )}$

Finally, if a third observer (Charles, say) comes along and measures Alice, Bob, and their respective particles, he will find that everyone still agrees, because his own “coherence-operator” demands that

${\displaystyle M_{C}(A)=M_{C}(\alpha )}$ and ${\displaystyle M_{C}(B)=M_{C}(\beta )}$

while knowledge that the particles were in a singlet state tells him that

${\displaystyle M_{C}(\alpha )+M_{C}(\beta )=0.}$

Thus the relational interpretation, by shedding the notion of an “absolute state” of the system, allows for an analysis of the EPR paradox which neither violates traditional locality constraints, nor implies superluminal information transfer, since we can assume that all observers are moving at comfortable sub-light velocities. And, most importantly, the results of every observer are in full accordance with those expected by conventional quantum mechanics.

— Wikipedia on Relational quantum mechanics

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2018.10.22 Monday ACHK

# The Sixth Sense, 3

Mirror selves, 2 | Anatta 3.2 | 無我 3.2

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You cannot feel your own existence or non-existence. You can feel the existence or non-existence of (such as) your hair, your hands, etc.

But you cannot feel the existence or non-existence of _you_.

— Me@2018-03-17 5:12 PM

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Only OTHER people or beings can feel your existence or non-existence.

— Me@2018-04-30 11:29:08 AM

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# Logical arrow of time, 6.2

Source of time asymmetry in macroscopic physical systems

Second law of thermodynamics

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— Bohr

— paraphrased

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Physics should deduce what an observer would observe,

not what it really is, for that would be impossible.

— Me@2018-02-02 12:15:38 AM

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2. Whatever an observer can observe is a consistent history.

observer ~ a consistent story

observing ~ gathering a consistent story from the quantum reality

3. Physics [relativity and quantum mechanics] is also about the consistency of results of any two observers _when_, but not before, they compare those results, observational or experimental.

4. That consistency is guaranteed because the comparison of results itself can be regarded as a physical event, which can be observed by a third observer, aka a meta observer.

Since whenever an observer can observe is consistent, the meta-observer would see that the two observers have consistent observational results.

5. Either original observers is one of the possible meta-observers, since it certainly would be witnessing the comparison process of the observation data.

— Me@2018-02-02 10:25:05 PM

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# The Sixth Sense, 2

It is difficult only for the others.

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It is also true when you are stupid.

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2018.01.26 Friday ACHK