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


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



2019.02.11 Monday (c) All rights reserved by ACHK

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.


— 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 —


— Me@2013-10-25 3:33 AM


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



2019.01.19 Saturday (c) All rights reserved by ACHK

宇宙大戰 1.2

PhD, 2.4 | 故事連線 1.1.6 | 碩士 3.4
















— Me@2019-01-01 11:20:57 PM



2019.01.01 Tuesday (c) All rights reserved by ACHK

宇宙大戰 1.1

PhD, 2.3 | 故事連線 1.1.5 | 碩士 3.3
























— Me@2018-12-20 11:06:49 PM



2018.12.20 Thursday (c) All rights reserved by ACHK

Relational quantum mechanics

EPR paradox, 10


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



2018.10.22 Monday ACHK

The Sixth Sense, 3

Mirror selves, 2 | Anatta 3.2 | 無我 3.2


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


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

— Me@2018-04-30 11:29:08 AM



2018.04.30 Monday (c) All rights reserved by ACHK

Logical arrow of time, 6.2

Source of time asymmetry in macroscopic physical systems

Second law of thermodynamics



Physics is not about reality, but about what one can say about reality.

— Bohr

— paraphrased



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



1. Physics is about what an observer can observe about reality.

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




2018.02.03 Saturday (c) All rights reserved by ACHK

The Dunning–Kruger effect

想不出來 1.2.2

The Dunning–Kruger effect is a cognitive bias in which low-ability individuals suffer from illusory superiority, mistakenly assessing their ability as much higher than it really is. Dunning and Kruger attributed this bias to a metacognitive incapacity, on the part of those with low ability, to recognize their ineptitude and evaluate their competence accurately. Their research also suggests corollaries: high-ability individuals may underestimate their relative competence and may erroneously assume that tasks which are easy for them are also easy for others.

Dunning and Kruger have postulated that the effect is the result of internal illusion in those of low ability, and external misperception in those of high ability: “The miscalibration of the incompetent stems from an error about the self, whereas the miscalibration of the highly competent stems from an error about others.”

— Wikipedia on Dunning–Kruger effect

I’ve found that people who are great at something are not so much convinced of their own greatness as mystified at why everyone else seems so incompetent.

— Paul Graham

2017.02.17 Friday ACHK


Do not be too timid and squeamish about your actions. All life is an experiment. The more experiments you make the better.

— Emerson

One experience [almost] always helps another, because the first experience betters you, to deal with the second experience; even if the first experience is unpleasant.

— Me@2011.07.16

— Me@2015.11.19

2015.11.19 Thursday (c) All rights reserved by ACHK

Quantum Indeterminacy

注定外外傳 1

Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics.

Indeterminacy in measurement was not an innovation of quantum mechanics, since it had been established early on by experimentalists that errors in measurement may lead to indeterminate outcomes. However, by the later half of the eighteenth century, measurement errors were well understood and it was known that they could either be reduced by better equipment or accounted for by statistical error models. In quantum mechanics, however, indeterminacy is of a much more fundamental nature, having nothing to do with errors or disturbance.

— Wikipedia on Quantum indeterminacy

Quantum indeterminacy is the inability to predict the behaviour of the system with 100% accuracy, even in principle.

If everything is connected , quantum indeterminacy is due to the logical fact that, by definition, a “part” cannot contain (all the information of) the “whole”.

An observer (A) cannot separate itself from the system (B) that it wants to observe, because an observation is an interaction between the observer and the observed .  

In order to get a perfect prediction of a measurement result, observer (A) must have all the information of the present state of the whole system (A+B). However, there are two logical difficulties.

First, observer A cannot have all the information about (A+B).

Second, observer A cannot observe itself to get (all of) its present state information, since an observation is an interaction between two entities. Logically, it is impossible for something to interact with itself directly. Just as logically, it is impossible for your right hand to hold your right hand itself. 

So the information observer A can get (to the greatest extent) is all the information about B, which is only part of the system (A+B) it (A) needs to know in order to get a prefect prediction for the evolution of the system B.

— Me@2015-09-14 08:12:32 PM

2015.09.15 Tuesday (c) All rights reserved by ACHK


stephengillie 64 days ago

In gaming, the concept is called a “replay”, where instead of recording the pixels on the screen in every frame, they instead record all inputs processed on every frame, and just replay them thru the same engine. The action is technically idempotent in the game world.

Where this breaks down is when features get updated between revisions. If your game patched the “jump” function to increase upward momentum from 1.1 m/s to 1.13 m/s, the Replay would be incorrect. You would be jumping onto platforms you couldn’t get up to before, moving faster, maybe even dodging enemy attacks that hit you when you played that match.

The human neuroprocessor is always changing and growing, always revising itself. Thus memories replay incorrectly. You apply old feelings to new mental patterns, and sometimes they lead to weird places. Or sometimes you mistake something easy for being difficult, because your memory data is out-of-date for your current processes. 

— Hacker News

2015.04.16 Thursday ACHK

What Is it Like to Be a Bat?

Feeling is a relationship between a particular observer and a particular observed.

So the question of “whether the color red I see is the same as the color red you see” is logically meaningless.

— Me@2015-04-06 1:13 PM

If observer B can get the memory of observer A, it is logically possible to feel another mind’s feelings (to a certain extend).

In that situation, the question of “whether B’s feeling of seeing the color red is the same as A’s” is meaningful.

— Me@2015-04-07 03:58:46 PM

2015.04.09 Thursday (c) All rights reserved by ACHK

Open Source MindOS

這段改編自 2010 年 4 月 10 日的對話。








那就即是話,你腦中的作業系統,是 Open Source 的 —— 容許別人修改。



— Me@2014.06.26


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.

— A History of Western Philosophy

— Bertrand Russell



2014.06.27 Friday (c) All rights reserved by ACHK


這段改編自 2010 年 4 月 10 日的對話。











— Me@2014.03.25

— Me@2014.03.31

2014.04.01 Tuesday (c) All rights reserved by ACHK

Universe 7

The universe as a whole is an un-observable for two reasons, one physical and one logical.

The physical reason is that the speed of light, while being the maximum possible signal transmission speed, is finite. However, the expansion of the universe, in a sense, is faster than the speed of light. So the light rays emitted by some objects can never reach your eyes, no matter how long you wait. You cannot observe everything at once at any particular moment of time.

The logical reason is that, for any observer, at least one thing in this universe it cannot observe: itself. You can never see yourself directly, just as a camera can never take a picture of itself directly.

— Me@2012-10-18 12:47:32 PM

— Me@2014-02-25 01:57:06 PM

2014.02.26 Wednesday (c) All rights reserved by ACHK