The 4 bugs of quantum mechanics popular, 1.5

Posted on February 22, 2022 by rpflee

3.1 Probability value is totally objective. Wrong.

A probability value is not only partially objective, but also partially subjective. When you get a probability value, you have to specify which observer the value is with respect to. Different observers can get different probabilities for the “same” event.

Also, the same observer at 2 different times should be regarded as 2 different observers.

For example, for a fair dice, before rolling, the probability of getting an 2 is $\displaystyle{\frac{1}{6}}$ . However, after rolling, the probability of getting an 2 is either $\displaystyle{0}$ or $\displaystyle{1}$ , not $\displaystyle{\frac{1}{6}}$ . So the same person before and after getting the result should be regarded as 2 different observers.

A major fault of the many-worlds interpretation of quantum mechanics is that it uses an unnecessarily complicated language to state an almost common sense fact that any probability value is partially subjective and thus must be with respect to an observer. There is no “god’s eye view” in physics.

— Me@2017-05-10 07:45:36 AM

— Me@2022-02-14 10:36:52 AM

Wave functions encode probabilities. So each wave function is partially objective and partially observer-dependent. In other words, a wave function encodes the relationship between a physical system and an observer/experimenter.

— Me@2022-02-20

The 4 bugs of quantum mechanics popular, 1.4

Posted on February 21, 2022 by rpflee

A misnomer collection:

2.2.1.

Wave function is not a wave. It is not a physical wave.

2.2.2.

Uncertainty principle is not about uncertainty. It is not directly related to uncertainty.

Uncertainty principle is not a principle. It is not even a physical law. Instead, it is a statistical relation. It is an inequality about the standard deviations of two conjugate variables.

2.2.3.

Superposition state is not a superposition. It is not a physical superposition. It is not a superposition of physical waves.

Superposition state is not a state. Instead, it is a property of a physical system. It is a statistical property of a variable of an experimental setup.

2.2.4.

Quantum mechanics is not quantum. It is not just about quantum (particle of energy).

Quantum mechanics is not mechanics. It is not just about mechanics. It is not just physical laws. Instead, it is a set of meta-laws, laws that physical laws themselves need to follow. It is an operating system on which physical laws can run.

— Me@2022-02-20 06:44:32 AM

The 4 bugs of quantum mechanics popular, 1.3

Posted on February 21, 2022 by rpflee

The common quantum mechanics “paradoxes” are induced by 4 main misunderstandings.

1. A wave function is of a particle. Wrong.

…

2.1 A system's wave function exists in physical spacetime. Wrong.

…

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

superposition

~ lack of the existence of measuring device to provide the physical definitions for the (difference between) microscopic events

— Me@2022-02-12 10:22:09 AM

a physical variable X is in a superposition state

~ X has no physical definition

~ in the experiment-setup design, no measurement device is allowed to exist to provide a definition of different possible values of X

— Me@2022-02-18 02:04:45 PM

2.2 A superposition state is a physical superposition of a physical state. Wrong.

“Quantum state” is a misnomer. It is not a (physical) state. It is a (mathematical) property. It is a system property (of a physical variable) of an experimental-setup design.

“State” and “property” have identical meanings except that:

State is physical. It exists in physical time. In other words, a system's state changes with time.

Property is mathematical. It is timeless. In other words, a system's property does not change. (If you insist on changing a system's property, that system will become, actually, another system.)

For example, “having two wheels” is a bicycle’s property; but the speed is a state, not a property of that bicycle.

superposition state

~ physically-undefined property

In the phrase “superposition state”, the word “superposition” is also a misnomer.

A superposition state is not of physical waves, nor of physical states. Instead, it is a superposition of physical meanings of some variables in a physical system.

a physical variable X is in a superposition state

~ X is a physically-undefined property (of the physical system)

— Me@2022-02-18 02:04:45 PM

— Me@2022-02-20 06:44:32 AM

The 4 bugs of quantum mechanics popular, 1.2

Posted on February 20, 2022 by rpflee

The common quantum mechanics “paradoxes” are induced by 4 main misunderstandings.

1. A wave function is of a particle. Wrong.

…

2.1 A system's wave function exists in physical spacetime. Wrong.

…

So a wave function (for a particular variable) is an intrinsic property of a system. It is a mathematical property, not a physical state, of the physical system (the experimental setup). It does not evolve in time.

A wave function looks like evolving in physical time because it is a (mathematical) function of time.

But being a mathematical function of time only means that you can use the wave function to calculate the probabilities of a physical variable having different particular values at different times.

.

An electromagnetic wave mathematical equation, which does not exist in physical spacetime, has its corresponding physical wave—-electromagnetic wave, which exists in physical spacetime.

However, a quantum wave function mathematical equation has no corresponding physical wave.

A wave function encodes a probability distribution; it can only correspond to a probability distribution, which is also a mathematical entity only.

A probability distribution can be a function of space and time. But that does not mean that the probability distribution exists in physical spacetime.

Any wave physical, such as electromagnetic wave, can be measured by a physical device.

In a sense, you cannot change a wave function; you can only replace it with another by replacing the physical system with another.

So whether the wave function of a variable is in superposition is an intrinsic property of a system, decided by the experiment’s designer.

Also, because of the existence of incompatible variable pairs, for any system, there must be some variables in a superposition, while others not.

— Me@2022-02-20 06:44:32 AM

The 4 bugs of quantum mechanics popular

Posted on February 19, 2022 by rpflee

The “para” in “paradox” means “meta”. The original meaning of the word “paradox” is

an error due to mixing language levels—-the object level and the meta level.

However, people have misused the word “paradox” a lot, using it to label anything unexpected. For example, in quantum mechanics, there are many so-called “paradoxes” that may be not really paradoxes.

However, among those quantum mechanics “paradoxes”, some of them are really paradoxes, whose existences are really due to mixing the object time level and the meta-time level.

The time within a story is called the “object time”. The time of the story’s writer or reader is called the “meta-time”.

The physical time in which an experiment is conducted is the object time. The time in which an experiment is designed is the meta-time. The meta-time of an experiment is its designer’s time level.

“Wave function collapse” is not a physical process. Instead, it is mathematical. It just means that we have to replace the wave function with another if we replace the system with another.

In other words, it is not a physical event that happens during the operation of the experiment. Instead, it “happens” when you replace one experiment design with another. In this sense, “wave function collapse” happens not in the experiment’s time, but in the experiment’s meta-time, the time level of the experiment designer.

wave function collapse

~ probability distribution change (replacement) due to replacing “the experiment without measurement device” with “the experiment with measuring device“ (for a particular physical variable)

The common quantum mechanics “paradoxes” are induced by 4 main misunderstandings.

1. A wave function is of a particle. Wrong.

Instead, it is of the system (the experiment setup). It is of a variable of the physical system.

Actually, a system has more than one wave functions. Each physical variable of that system has its own wave function.

2.1 A system's wave function exists in physical spacetime. Wrong.

Instead, the wave function exists in the mathematical abstract space. With respect to an individual physical variable, different physical systems give different probability distributions, which are encoded in different wave functions.

In a sense, you cannot change a wave function; you can only replace it with another by replacing the physical system with another.

— Me@2022-02-19 04:21:38 PM

Logical arrow of time, 6.4.3

Posted on February 18, 2022 by rpflee

Logical arrow of time, 6.1.3

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.

.

In other words:

In a prediction, the meta-time direction is the same as the object-time direction.

In a retrodiction, the meta-time direction is opposite to the object-time direction.

— Me@2022-02-18 06:52:27 AM

.

— 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

— Me@2013-10-25 3:33 AM

How to create a time-inverted observer?

Just invert the retrodiction direction.

Retrodiction to a backward-time observer is just equivalent to retrodiction-for-backward-time to a forward-time observer.

However, retrodiction-for-backward-time is just prediction.

In other words, retrodiction to a backward-time observer is equivalent to a prediction for a normal time direction observer.

That’s why

— 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

— Me@2013-10-25 3:33 AM

— Me@2022-02-18 06:37:59 AM

EPR paradox, 11.8

Posted on February 18, 2022 by rpflee

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

The second clue:

If in your experimental design, you have planned to activate a detector when each particle is still on its path, then this activation action itself is already part of your experimental design.

The detector and the planned action of activating it have already formed a “physical definition” that makes your experiment design to have the system being in a mixed state, instead of superposition state, since the beginning of the experiment.

Put it more accurately, since a wave function is a mathematical function, not a physical field, it does not exist in physical spacetime.

Superposition is a property for some wave functions (quantum states). So superposition is not a physical phenomenon. Instead, it is a mathematical property of some physical variables of your experimental-setup design.

In a sense, instead of existing at the time level of the experiment and the observer, a wave function exists at the meta-time level, the time level of the experiment-setup designer.

So it is meaningless to say “the experimental setup is in a superposition state (or not) in the beginning of the experiment”.

Instead, whether a system is in superposition or not (with respect to a particular variable) is an intrinsic property of your experimental setup design, which includes not just objects and devices, but also operations.

“Wave function collapse” is not a physical event that happens during the operation of the experiment. Instead, it “happens” when you replace one experiment design with another.

— Me@2022-02-16 10:45:01 AM

If the experimenter does not follow the original experiment design, such as not turning on the detector at the pre-defined time, then he is actually doing another experiment, which will have a completely different probability distribution (for any particular variable).

— Me@2022-02-14 10:35:27 AM

An experiment-setup design is composed of not only objects and devices, but also operations. A different experiment-setup design will give a different probability distribution for any particular physical variable.

Also, a different observer will see a different probability distribution for any particular physical variable. The same observer at different times actually should be regarded as different observers.

In other words, “where and when an observer should do what during the experiment” is actually part of your experimental-setup design, defining what probability distribution (for any particular variable) you (the observer) will get.

— Me@2022-02-18 07:40:14 AM

EPR paradox, 11.7

Posted on February 17, 2022 by rpflee

…

Even in this stranger case, all experimental results are still consistent with special relativity (aka causality), because wave functions are not physical quantities. Instead, they are mathematical quantities for calculating probabilities, which themselves are also mathematical quantities, for predicting experimental results.

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

(Me@2022-02-17 03:34:27 PM: I think I have the answer now. I plan to publish it soon. But I keep the following as a record of thoughts.)

A further strangeness is that

~ How come the results are always consistent when the EPR pair has no definite states before ~~measurement~~ the activation of at least one detector?

~ How does the universe to do such bookkeeping for a system exists across several light-years when the physical variables are still in superposition when the pair is emitted from the source?

~ … when the difference of possible values (such as the difference of spin-up and spin-down) still have no physical definition yet?

~ … when the difference of possible values have not yet defined by the difference of possible readings of a detector (before any detector is allowed to be installed-and-activated)

However, this kind of strangeness also happens in classical physics, for example:

1. How come energy is always conserved? How is energy conservation “executed”?

2. How does probability work? How does the universe work to fulfill the predicted probability patterns?

— Me@2022-02-11 12:47:14 AM

A clue (but not yet the whole final solution) is that probability is with respect to observers.

— Me@2022-02-11 10:13:36 AM

A probability is partially objective and partially subjective. So a wave function, which is used for calculating probabilities, is also partially objective and partially subjective.

A major fault of the many-worlds interpretation of quantum mechanics is that it uses an unnecessarily complicated language to state an almost common sense fact that any probability value is partially subjective and thus must be with respect to an observer.

— Me@2022-02-14 10:36:52 AM

— Me@2022-02-14 10:35:27 AM

EPR paradox, 11.6

Posted on February 16, 2022 by rpflee

What is more difficult to understand is the non-classical part:

What if, instead of turning on a detector before the time of emitting, we turn it on after the pair is emitted but before either of them has reached its destination?

…

In the common (but inaccurate) language, the action of activating a detector has collapsed the wave function of the system.

Would the pair of (such as) spin values be correlated?

(Me@2022-02-16 12:07:25 AM: I think I have the answer now. I plan to publish it soon. But I keep the following as a record of thoughts.)

There are 2 possibilities.

(I do not know which of them is true, because I have not yet found an actual experiment that has tested against them.)

[guess]

They are correlated only in the statistical sense.

…

Every pair is correlated.

This is stranger than the first case, because if the two detectors are several light-years apart, the whole system exists across those light-years. The strangeness is the fact that even for a system-across-light-years, operations at one end can influence the probability of an event at the other end.

For the time being, I guess that the second case is the true one.

Even if the first case is the true one, it is still strange because it implies that an action at one part of the system influences the statistical properties of another part, which may be several light-years away.

[guess]

— Me@2022-02-11 12:47:14 AM

Bug fixes:

1.1 It is not the particle’s state that is in a superposition or not, but the system’s state.

2.1 We need to specify which observer that the wave function is with respect to.

A wave function is for an observer to calculate the probabilities of different possible results in an experiment.

2.2 There is no “god’s eye view” in physics.

Every physical event must be described with respect to an observer. Every physical event, even if the event is “to compare observation results”, must be described with respect to an observer. — Me@2017-05-10 07:45:36 AM

2.3 A wave function is mathematical, not physical.

It is a mathematical function for an observer to calculate the probabilities. It is not something existing in physical spacetime. Thus superposition is also not something existing in physical spacetime. So it is meaningless to ask if the system state is in a superposition at a particular time.

Instead, whether a system is in superposition or not (with respect to a particular variable) is an intrinsic property of your experimental setup design, which includes not just objects and devices, but also operations.

“Wave function collapse” is not a physical event that happens during the operation of the experiment. Instead, it “happens” when you replace one experiment design with another.

— Me@2022-02-16 10:45:01 AM

EPR paradox, 11.5

Posted on February 16, 2022 by rpflee

Black hole information paradox, 2.2.5

What is more difficult to understand is the non-classical part:

What if, instead of turning on a detector before the time of emitting, we turn it on after the pair is emitted but before either of them has reached its destination?

Since neither of the detectors at the two end destinations is activated in the beginning, the entangle variables are still physically-undefined (i.e. in a superposition) at that moment the pair is emitted.

However, while the particles are still on the way, at the moment one of two detectors is first activated, the entangled variables get their physical definitions. The system state is no longer in a superposition state. Instead, it becomes a mixed state. In other words, the system has become a classical system (with respect to those entangled variables).

In the common (but inaccurate) language, the action of activating a detector has collapsed the wave function of the system.

Would the pair of (such as) spin values be correlated?

(Me@2022-02-16 12:07:25 AM: I think I have the answer now. I plan to publish it soon. But I keep the following as a record of thoughts.)

There are 2 possibilities.

(I do not know which of them is true, because I have not yet found an actual experiment that has tested against them.)

[guess]

They are correlated only in the statistical sense.

Individual pair of values may be not correlated, but a lot of pairs that have the same superposition (at time of emitting) will form that statistical pattern that is indistinguishable from the one that predicted with the assumption that every pair is correlated.

In analogy, in the double-slit experiment, an individual dot on the final screen cannot tell whether the particle was in a superposition. It is only after a lot of dots forming on the final screen, we can check whether there is an interference pattern. When the interference appears (and we assume that the wave function that governs every particle is the same), we say that every particle is in a superposition state. Or put it more accurately, the system is in the same superposition state before each particle has reached the screen.

Every pair is correlated.

[guess]

— Me@2022-02-11 12:47:14 AM

EPR paradox, 11.4

Posted on February 14, 2022 by rpflee

Black hole information paradox, 2.2.4

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

In the EPR experiment, if at least one of the detectors at the two end destinations is already turned on at the time of emitting, then (the system that contains) the pair is NOT in a superposition since the beginning.

The entangled variables (that the detector measures) are already physically defined by the detector’s potential behaviors. The system state is already a mixed state, not a superposition.

superposition

~ lack of the existence of measuring device to provide the physical definitions for the (difference between) microscopic events

— Me@2022-01-31 08:33:01 AM

— Me@2022-02-12 10:22:09 AM

With respect to that pair of entangled variables, the experiment setup is just a classical one, which directly follows Aristotle’s 3 laws of logic.

For any proposition $\displaystyle{A}$ , either $\displaystyle{A}$ is true or $\displaystyle{\text{NOT}~A}$ is true, but not both.

There is nothing non-classical about the correlation between the (such as) spin values of the pair.

What is more difficult to understand is the non-classical part:

What if, instead of turning on a detector before the time of emitting, we turn it on after the pair is emitted but before either of them has reached its destination?

— Me@2022-02-11 12:47:14 AM

EPR paradox, 11.3

Posted on February 13, 2022 by rpflee

Black hole information paradox, 2.2.3

It shouldn’t be so surprising that unitarity survives completely while causality doesn’t. After all, the basic postulates of quantum mechanics, including unitarity, the probabilistic interpretation of the amplitudes, and the linearity of the operators representing observables, seem to be universally necessary to describe physics of any system that agrees with the basic insights of the quantum revolution.

On the other hand, geometry has been downgraded into an effective, approximate, emergent aspect of reality. The metric tensor is just one among many fields in our effective field theories including gravity.

— Black hole information puzzle

— Lubos Motl

identical particles

~ some particles are identical, except having different positions

~ some particle trajectories are indistinguishable

.

trajectory indistinguishability

~ particle identity is an approximate concept

~ causality is an approximation

.

spacetime is defined by causality

~ so spacetime is also an approximation

— Me@2022-02-11 12:47:14 AM

— Me@2022-02-13 03:38:35 PM

EPR paradox, 11.2

Posted on February 12, 2022 by rpflee

Black hole information paradox, 2.2.2

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

.

superposition

~ lack of the existence of measuring device to provide the physical definitions for the (difference between) microscopic events

— Me@2022-01-31 08:33:01 AM

— Me@2022-02-12 10:22:09 AM

In the EPR experiment, how come the two always correlate if there are no definite states before the measurements?

When you actually know the results of your experiment, it does affect your expectations of the faraway results if there are correlations – and correlations are almost always there iff the two subsystems have interacted or been in contact in the past). — Lubos Motl

Microscopically, there is no time, in the sense that all the (past and future) quantum states have one-one correspondences. All results are deterministic. No causality violation required nor allowed. — Me@2016-10-14 07:55:48 PM

This is called quantum determinism, which may or may not be correct. But quantum determinism, even if true, is not necessary for explaining the EPR experiment, if we understand that:

1. Superposition is mathematical, not physical.

2. “Wave function collapse” is mathematical, not physical. It just means that we have to replace the wave function with another if we replace the system with another.

The system before and after the detectors activated should be regarded as two distinct systems. In other words, when you activate the detectors, you have actually replaced a system-without-detectors with a system-with-detectors.

“Wave function collapse” replaces the pure state wave function with a mixed state wave function. In other words, it replaces the pure state of superposition with a mixed state of eigenstates. In other other words, it replaces quantum probability with classical probability.

Before opening the box, the cat is not in a superposition state. Instead, it is in a mixed state.

The uncertainty is classical probability, which is due to lack of detailed knowledge, not quantum probability, which is due to lack of definition (in terms of physical phenomena difference).

— Me@2022-01-29 10:38:19 PM

— Me@2022-02-12 10:28:57 AM

EPR paradox, 11.1

Posted on February 11, 2022 by rpflee

Black hole information paradox, 2.2.1

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

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

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

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

.

a definite state

~ an eigenstate

~ a state that has given a physical definition

— Me@2022-02-11 01:19:57 PM

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 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

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

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

時光起源

Posted on January 5, 2022 by rpflee

The Origin of Time

這段改編自 2021 年 12 月 5 日的對話。

昨日的那段影片說，個別的粒子，其實都是質量零；以光速行走，感受不到時間。

但是，把一堆粒子圈成一件東西的話，那件東西整體而言，就會有質量；就會低於光速行走；就會感受到時間。

變相來說，時間的來源就是，你將一堆粒子組成一個物件、一個身份、一個自我時，那個自我就會，感受到時間。

— Me@2022-01-04 12:23:25 PM

To form an object (an observer), the component particles cannot all always move at light speed in the same direction, for that would prevent the object as a whole from feeling time.

Anything moving at the speed of light cannot feel the passage of time. If a set of particles all moves at light speed in the same direction all the time, they cannot feel time either as individuals or as a whole; so they cannot form an “object”.

To form an object (an observer), the component particles need to interact. So some component particles need to move in other directions sometimes.

An object requires an internal structure to exist and evolve. The component particles need to interact in order to evolve as a single identity. So different particles need to move in different directions sometimes. As a result, the component particles as a whole, aka “the object”, will move slower than light.

— Me@2021-12-08 08:09:17 AM

Logical arrow of time, 9.4

Posted on August 7, 2021 by rpflee

The second law of thermodynamics’ derivation (Ludwig Boltzmann’s H-theorem) is with respect to an observer.

How does an observer keep losing microscopic information about a system?

— Me@2017-02-12 07:37:54 PM

This drew the objection from Loschmidt that it should not be possible to deduce an irreversible process from time-symmetric dynamics and a time-symmetric formalism: something must be wrong (Loschmidt’s paradox).

The resolution (1895) of this paradox is that the velocities of two particles after a collision are no longer truly uncorrelated. By asserting that it was acceptable to ignore these correlations in the population at times after the initial time, Boltzmann had introduced an element of time asymmetry through the formalism of his calculation.

— Wikipedia on Molecular chaos

Physical entropy’s value is with respect to an observer.

— Me@2017-02-12 07:37:54 PM

This “paradox” can be explained by carefully considering the definition of entropy. In particular, as concisely explained by Edwin Thompson Jaynes, definitions of entropy are arbitrary.

As a central example in Jaynes’ paper points out, one can develop a theory that treats two gases as similar even if those gases may in reality be distinguished through sufficiently detailed measurement. As long as we do not perform these detailed measurements, the theory will have no internal inconsistencies. (In other words, it does not matter that we call gases A and B by the same name if we have not yet discovered that they are distinct.) If our theory calls gases A and B the same, then entropy does not change when we mix them. If our theory calls gases A and B different, then entropy does increase when they are mixed. This insight suggests that the ideas of “thermodynamic state” and of “entropy” are somewhat subjective.

— Wikipedia on The mixing paradox

— Wikipedia on Gibbs paradox

Causal diamonds in time travel

Posted on April 17, 2021 by rpflee

Quantum mechanics is a set of rules that allows an observer to predict, explain, and/or verify observations (and especially their mutual relationships) that he has access to.

…

No observer can detect inconsistencies within the causal diamonds. However, inconsistencies between “stories” as told by different observers with different causal diamonds are allowed (and mildly encouraged) in general (as long as there is no observer who could incorporate all the data needed to see an inconsistency).

— Raphael Bousso is right about firewalls

— Lubos Motl

There is no “god’s eye view” in physics.

— Me@2021-04-17 03:12:58 PM

Macroscopic time is with respect to an observer. Actually, physics is with respect to an observer.

In the real universe, any observer’s observations must be consistent. When two observers compare their observations, their results must be consistent, because the comparison itself is an observation of an observer.

Time travel in the absolute sense is logically impossible. Let’s assume that it is logically possible.

If a time travel story follows the principle of “an observer’s observations must be consistent”, each character in that story must see a consistent timeline, even if different characters’ timelines may be inconsistent. That is fine as long as such inconsistent observers never meet to compare their results.

If two of such observers choose to meet to compare their results, the action to “meet to compare” itself will render the results consistent. It is similar to the resolution of the twin paradox in special relativity.

There is no “god’s eye view” in physics. Every physical event must be described with respect to an observer. Every physical event, even if the event is “to compare observation results”, must be described with respect to an observer.

— Me@2017-05-10 07:45:36 AM

Universal wave function, 21

Posted on April 9, 2021 by rpflee

For all, 9

A problem of universal wave function (universe) is that universe is a relative concept.

Another problem is that wave function is also.

— Me@2017-05-10 05:46:44 PM

— Me@2021-04-09 06:25:07 PM

universe ~ 100%

But 100% of what?

— Me@2021-04-09 05:20:23 PM

The wave function is expressed in terms of basis state vectors.

So it will have a different form if you choose a different basis.

— Me@2021-04-09 06:29:20 PM

Logical arrow of time, 9.1

Posted on April 4, 2021 by rpflee

The source of asymmetry:

For prediction of the future, the result is what the observer/calculator can actually see.

For retrodiction of the past, the result is not.

— Me@2017-07-09 12:03:27 PM

— Me@2021-04-04 12:28:34 PM

Conscious time, 2

Posted on March 30, 2021 by rpflee

If no one has any kind of date, records, memories, or evidence about the past, retro-diction MAY be the same as prediction. But in such a case, it is by definition not our “past” any more.

— Me@2013-08-08 3:11 PM

If no one has any kind of date, records, memories, or evidence about the past, then consciousness ceases to exist.

We, as conscious beings, cannot exist anymore.

— Me@2021-03-30 4:08 PM

Physics Town

continues

Category Archives: quantum decoherence

The 4 bugs of quantum mechanics popular, 1.5

The 4 bugs of quantum mechanics popular, 1.4

The 4 bugs of quantum mechanics popular, 1.3

The 4 bugs of quantum mechanics popular, 1.2

The 4 bugs of quantum mechanics popular

Logical arrow of time, 6.4.3

EPR paradox, 11.8

EPR paradox, 11.7

EPR paradox, 11.6

EPR paradox, 11.5

EPR paradox, 11.4

EPR paradox, 11.3

EPR paradox, 11.2

EPR paradox, 11.1

時光起源

Logical arrow of time, 9.4

Causal diamonds in time travel

Universal wave function, 21

Logical arrow of time, 9.1

Conscious time, 2