# Quantum weirdness



## KenOC (Mar 7, 2011)

Some interesting stuff that I don't begin to understand! But maybe people can post videos, experiments, or results here.

I'll start with the "delayed choice quantum eraser," an actual experiment that shows future events influencing events in the past. This shouldn't happen! (But it evidently does.) Even the presenter is puzzled.

The presentation is clear and easy to follow through animations.


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## Dim7 (Apr 24, 2009)

Probably better to familiarize oneself with the classic double slit experiment before watching that. Also quantum entanglement, as it is used in the experiment. Which by itself, being (at least seemingly so) "faster than light" causal influence, implies causal influence to the past from certain frames of reference (according to the theory of relativity). If I'm not mistaken.


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## KenOC (Mar 7, 2011)

The special theory of relativity also seems to imply that the future is fixed and already determined. This arises from the theory’s prediction that observers in certain frames of reference will see our own future before we experience it. The idea that the passage of time is simply travel through a pre-defined universe is expressed in the “block universe" theory.

Well, that's not quantum weirdness, but I guess it's weird enough!


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## Bwv 1080 (Dec 31, 2018)

SR does not imply the future is fixed or is visible

If you google "delayed choice quantum eraser" there is alot of science arguing against any alteration of past events

https://algassert.com/quantum/2016/01/07/Delayed-Choice-Quantum-Erasure.html


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## Jacck (Dec 24, 2017)

KenOC said:


> The special theory of relativity also seems to imply that the future is fixed and already determined. This arises from the theory's prediction that observers in certain frames of reference will see our own future before we experience it. The idea that the passage of time is simply travel through a pre-defined universe is expressed in the "block theory" of the universe.
> 
> Well, that's not quantum weirdness, but I guess it's weird enough!


The experiment in the video is misrepresented. There is no information coming from the future to influence the past. And there is no superliminal information transfered anywhere in quantum mechanics. If it did, it would lead to temporal paradoxes such as the grandfather paradox. The reason is that in relativity theory there is something called the relativity of simultaneity and superluminal communication would break it. And special theory of relativity is an incredibly well tested theory. But there are some mysterious correlations between measurements of entangled particles, but these correlations cannot be used to transfer any information whatsoever (for the above stated reason).

My favorite "quantum weirdness" experiment is the GHZ experiment. It is virtually unknown, but I have had 4 semesters of quantum mechanics and studying quantum weirdness has been my main motivation for physics study. It is a bit technical, but you can understand its essence from this nontechnical paper
https://www.tau.ac.il/~vaidman/lvhp/m71.pdf
http://www.physics.smu.edu/scalise/P5382fa15/Mermin1990a.pdf
David Mermin in general is a very good author on this quantum weirdness. 
Or Anton Zeilinger
https://www.amazon.com/Dance-Photons-Einstein-Quantum-Teleportation/dp/0374239665


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## Art Rock (Nov 28, 2009)

Somewhat related, in terms of whether the future is fixed or not:

I've had a number of detailed "visions" or "notions" in the past that came true quickly afterwards - coincidence or not?

Once I was listening from the 10th floor in a Houston hotel to a girl playing the piano in the foyer. She played typical American songbook stuff, without music sheets in front of her. I thought: "what would be nice now if she would play some Chopin, preferably the famous etude (op.10.3, or the way I thought about it "In mir klingt ein Lied"). Once she finished what she was playing, she took out a book with music sheets and started to play exactly that etude's melody.

When I was watching the football/soccer worldcup final 1994 on TV (Brazil-Italy, live) with my brother, I told him during kick-off: it will remain 0-0, go to a penalty shootout and Baggio will miss the decider. Exactly what happened 2 hours later.

Now, both can be dismissed as pure coincidence of course, although the details are remarkable.

However, as a teenager, I once pulled out my bicycle from the shed in the garden to go to school, and found that the wooden racks in the shed had fallen down, and flowerpots that had been stored on them were in smithereens all over the floor. When I came back late afternoon, the racks were up where they were supposed to be, and the flowerpots all OK. I dismissed this as "probably I was not quite awake this morning". The next day, the same thing - but this time the damage was still there when I came back. Together with my parents, I cleaned up the mess. Somehow I had seen a day into the future that first morning.


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## Guest (Jul 15, 2019)

KenOC said:


> The special theory of relativity also seems to imply that the future is fixed and already determined. This arises from the theory's prediction that observers in certain frames of reference will see our own future before we experience it. The idea that the passage of time is simply travel through a pre-defined universe is expressed in the "block theory" of the universe.
> 
> Well, that's not quantum weirdness, but I guess it's weird enough!


That bit about other observers seeing our own future "before" we experience it does not ring true for me. There is no such thing as "simultaneous" events unless they occur at the same location and so there is no such thing as "before" or "after" except at the same location. If an event happens before another event at a certain location the order of the events is not altered by any change of reference frame. Maybe you can cook up a scenario where a remote observer in (relatively) moving reference frame has a local time which is before your local time of an event in your future. That is a clock synchronization issue, not a causality issue, I think.

I think a stronger argument for "block time" is quantum mechanics, where entanglement can make it seem that a measurement at point A affects a measurement at point B, with implied transmission of information faster than the speed of light. That can make it seem that a measurement changes the past (in some frame of reference).

I think the salient point is that there is no way to experimentally tell if the future is fungible (we have free will) or if we are just watching the unfolding of time that already exists. (Was it predestined since the beginning of the universe that I would have a bagel this morning, or did I decide to have a bagel?) That puts it in the regime of philosophical mumbo-jumbo, not science. I don't expect a scientific answer to the question.


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## KenOC (Mar 7, 2011)

The Chinese are working hard on quantum entanglement. Two years ago:

"Less than a year after they launched the world's only quantum communications satellite, Chinese researchers have for the first time ever sent entangled photons from space to ground stations on Earth…

"Now, entanglement has been preserved in pairs of photons sent by the Chinese satellite Micius to ground stations separated by 1203 kilometres - a new record."


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## Jacck (Dec 24, 2017)

more from Mermin...
Is the moon there when nobody looks? Reality and the quantum theory
http://www-f1.ijs.si/~ramsak/km1/mermin.moon.pdf
What is quantum mechanics trying to tell us?
http://web.pdx.edu/~pmoeck/lectures/mermin_amjphys1998.pdf


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## Jacck (Dec 24, 2017)

Baron Scarpia said:


> That bit about other observers seeing our own future "before" we experience it does not ring true for me. There is no such thing as "simultaneous" events unless they occur at the same location and so there is no such thing as "before" or "after" except at the same location. If an event happens before another event at a certain location the order of the events is not altered by any change of reference frame. Maybe you can cook up a scenario where a remote observer in (relatively) moving reference frame has a local time which is before your local time of an event in your future. That is a clock synchronization issue, not a causality issue, I think.
> 
> I think a stronger argument for "block time" is quantum mechanics, where entanglement can make it seem that a measurement at point A affects a measurement at point B, with implied transmission of information faster than the speed of light. That can make it seem that a measurement changes the past (in some frame of reference).
> 
> I think the salient point is that there is no way to experimentally tell if the future is fungible (we have free will) or if we are just watching the unfolding of time that already exists. *(Was it predestined since the beginning of the universe that I would have a bagel this morning, or did I decide to have a bagel?) That puts it in the regime of philosophical mumbo-jumbo, not science. I don't expect a scientific answer to the question*.


in fact there are some scientific theorems about it
https://www.ams.org/notices/200902/rtx090200226p.pdf


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## Guest (Jul 15, 2019)

Jacck said:


> in fact there are some scientific theorems about it
> https://www.ams.org/notices/200902/rtx090200226p.pdf


There are too many things I don't understand to spend time trying to understand theorems about free will. Even if such a theorem is valid (which I seriously doubt) I have no control over whether I have free will or not, so it is not a matter of concern to me.


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## CnC Bartok (Jun 5, 2017)

Art Rock said:


> Somewhat related, in terms of whether the future is fixed or not:
> 
> I've had a number of detailed "visions" or "notions" in the past that came true quickly afterwards - coincidence or not?
> 
> ...


I suspect this may be more useful than Einstein, Heisenberg, Feynman et al....


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## Luchesi (Mar 15, 2013)

CnC Bartok said:


> I suspect this may be more useful than Einstein, Heisenberg, Feynman et al....
> 
> Since time stops at the speed of light, what is time? Is it just merely a human convention or an imagined term like all those others (souls, unicorns, talent) which we're supposed to immediately understand and accept without any real understanding?
> 
> Time is just change. If we could put everything in the universe back the way it was yesterday, it would be yesterday, and not today (or tomorrow) .


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## Jacck (Dec 24, 2017)

Time is certainly one of the most enigmatic things. One of the interesting things about it is that it seems to be interchangable with space, hence the real entity seems to be spacetime. And different observers in the universe slice this spacetime in different coordinate systems.


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## Jacck (Dec 24, 2017)

The Quantum Experiment that Broke Reality 




this guy is good. He obviously knows what he is talking about, and he presents it without dumbing it down, as it is common with most popular science programs. Many of those have flashy graphics that only distract from the essence.


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## Luchesi (Mar 15, 2013)

Jacck said:


> Time is certainly one of the most enigmatic things. One of the interesting things about it is that it seems to be interchangable with space, hence the real entity seems to be spacetime. And different observers in the universe slice this spacetime in different coordinate systems.


Time as we watch it is merely one frame of positions and changes after another. Time is not any thing, because its direction is the same forward and backward (I mean,forward and backward in this sense is no such thing). It's merely simpler and more efficient to talk of time as if time has an existence.


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## Jacck (Dec 24, 2017)

Luchesi said:


> Time as we watch it is merely one frame of positions and changes after another. Time is not any thing, because its direction is the same forward and backward (I mean,forward and backward in this sense is no such thing). It's merely simpler and more efficient to talk of time as if time has an existence.


many physicists believe that space is not a thing either, that it is emergent out of something deeper. For example Nima Arkani-Hamed who is one of the most respected living theoretical physicists


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## Jacck (Dec 24, 2017)

BTW, it is always much better to listen to Nima - if you can follow him - than to Kaku


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## Jacck (Dec 24, 2017)

Freeman Dyson, legendary theoretical physicist, dies at 96
https://www.nationalgeographic.com/...n-legendary-theoretical-physicist-dies-at-96/


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## Strange Magic (Sep 14, 2015)

Freeman Dyson, his sometimes-estranged kayaking son George, and Dyson's physics partner Richard Feynman, are all found in one of the most enjoyable and engaging books I ever read, _The Starship and the Canoe_, by Kenneth Brower. Ken Brower, son of the environmental firebrand David Brower, became intrigued by the stories he had heard about George Dyson, the idiosyncratic kayak builder who lived high in a tree, befriended him, and--one thing leading to another--wrote a wonderful book that introduced me and many others to marvelous people.

Freeman Dyson was a strange bird, with a real mix of good, bad, and nutty ideas. Very English, though spending most of his life in the USA at the Institute for Advanced Study. Some say he should have won a Nobel along with Feynman and Schwinger but it seems he was more of a facilitator and catalyst rather than originator to Feynman and Schwinger in working out a final framework for quantum electrodynamics--sort of like David Hilbert to Einstein in formulating General Relativity.


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## Tikoo Tuba (Oct 15, 2018)

We need to realize instant communication/information . A telescope only gives us history . Surely , the existential and universal moment exists .


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## Phil loves classical (Feb 8, 2017)

I have a theory. That light is both a wave and particles the same time, not either/or. Imagine you holding a garden hose and you shake the hose back and forth. The water drops represent particles, and the oscillating pattern of the shaking back and forth will produce something like a sine wave. It's basic science that certain wavelengths /frequencies produce certain colours. The fact white light contains all those wave lengths the same time is through a type of multiplexing, the same way that data signals are combined in transmission over a single optical fiber, or other medium. So light consists of many hoses shaking at different rates. 

The reasoning of the quantum eraser is flawed since it assumes the light is either wave or particle at a given moment or instance. Those photons that get split and detected at various detectors share the same properties (same phase angle, etc.). So it's no wonder they behave the same way. It isn't that the result of one detector predicts the results of the another, and the results are the same with or without delay. The moment the photons go through the slits at a certain pinpoint location, they share the same properties.


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## aleazk (Sep 30, 2011)

Phil loves classical said:


> I have a theory. *That light is both a wave and particles the same time, not either/or*. Imagine you holding a garden hose and you shake the hose back and forth. The water drops represent particles, and the oscillating pattern of the shaking back and forth will produce something like a sine wave. It's basic science that certain wavelengths /frequencies produce certain colours. The fact white light contains all those wave lengths the same time is through a type of multiplexing, the same way that data signals are combined in transmission over a single optical fiber, or other medium. So light consists of many hoses shaking at different rates.
> 
> The reasoning of the quantum eraser is flawed since it assumes the light is either wave or particle at a given moment or instance. Those photons that get split and detected at various detectors share the same properties (same phase angle, etc.). So it's no wonder they behave the same way. It isn't that the result of one detector predicts the results of the another, and the results are the same with or without delay. The moment the photons go through the slits at a certain pinpoint location, they share the same properties.


That's simply not possible in quantum mechanics. A quantum system behaves in a wave-like way when its state after passing through the slits is a position eigenstate (the position of the slits), and in a particle-like/localized way when its state has a definite direction angle with respect to the orthogonal direction to the plane containig the slits, i.e., is an eigenstate of linear momentum p. But, since according to the fundamental relation of quantum mechanics [x,p]=i, that's is, momentum and position don't commute, then there isn't any state that can be an eigenstate of both p and position x at the same time. See this for the details.


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## Phil loves classical (Feb 8, 2017)

aleazk said:


> That's simply not possible in quantum mechanics. A quantum system behaves in a wave-like way when its state after passing through the slits is a position eigenstate (the position of the slits), and in a particle-like/localized way when its state has a definite direction angle with respect to the orthogonal direction to the plane containig the slits, i.e., is an eigenstate of linear momentum p. But, since according to the fundamental relation of quantum mechanics [x,p]=i, that's is, momentum and position don't commute, then there isn't any state that can be an eigenstate of both p and position x at the same time. See this for the details.


From what I understand what you're saying and from the paper, I'm not implying an individual particle or photon has wave-like properties in a localized way, but that the wave function of light is what determines the instances of angle/momentum properties of specific particles. Although the wave and particles properties can be separately observed, they are not necessarily independent.


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## Jacck (Dec 24, 2017)

Phil loves classical said:


> From what I understand what you're saying and from the paper, I'm not implying an individual particle or photon has wave-like properties in a localized way, but that the wave function of light is what determines the instances of angle/momentum properties of specific particles. Although the wave and particles properties can be separately observed, they are not necessarily independent.


from what I understand it is a property of the Fourier transform
https://chem.libretexts.org/Bookshe...Quantum_Mechanics_and_the_Fourier_Transfor m


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## Luchesi (Mar 15, 2013)

If what we experience as bits of mass (particles) are merely bumps in their respective fields then it gets very murky to describe what's going on. It's an extremely foreign world to us, but I guess it has to be this way for the universe to come out of nothing but spacetime. 

I like the idea that as the particle is observed - it's already in a new universe (a new timeline) and we’re dragged along with it. I mean, the act of observing drags us into a new timeline in the Many Worlds interpretation and there's no going back to our earlier universe. How else could it be?


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## aleazk (Sep 30, 2011)

Phil loves classical said:


> From what I understand what you're saying and from the paper, I'm not implying an individual particle or photon has wave-like properties in a localized way, but that *the wave function of light is what determines the instances of angle/momentum properties of specific particles. Although the wave and particles properties can be separately observed, they are not necessarily independent.*


Mm, what you say sounds somewhat similar to the pilot wave theory.


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## Sad Al (Feb 27, 2020)

The Many Worlds interpretation is very cheap. Everyone has one


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## Luchesi (Mar 15, 2013)

Sad Al said:


> The Many Worlds interpretation is very cheap. Everyone has one


You like one universe and nothing else was ever outside of it?

Welcome to the forum!


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## aleazk (Sep 30, 2011)

Luchesi said:


> *Time as we watch it is merely one frame of positions and changes after another.* Time is not any thing, because its direction is the same forward and backward (I mean,forward and backward in this sense is no such thing). It's merely simpler and more efficient to talk of time as if time has an existence.


I agree. Actually, that's a _relational_ view of time, that is, you use matter and its changing states to define time. I have done, and still doing, work about the role in quantum gravity of relational space and time.


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## Jacck (Dec 24, 2017)

aleazk said:


> I agree. Actually, that's a _relational_ view of time, that is, you use matter and its changing states to define time. I have done, and still doing, work about the role in quantum gravity of relational space and time.


matter does not exist, there are only quantum fields with their creation and annihilation operators. And how do you use those to define time? But there is likely something off with our theries, when the measured and the computed values of the cosmological contant differ by 120 orders of magnitude :lol:


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## aleazk (Sep 30, 2011)

Jacck said:


> matter does not exist, there are only quantum fields with their creation and annihilation operators. And how do you use those to define time? But there is likely something off with our theries, when the measured and the computed values of the cosmological contant differ by 120 orders of magnitude :lol:


Quantum fields are matter. I define matter as any thing that can carry energy. Quantum fields carry energy, therefore are matter. My work is indeed done using quantum fields. At the level of classical fields, you can define spacetime in a straightforward way. At the level of the quantized gravitational field, so far I have been able only to define space. I'm working on an idea for time, but so far is only an idea.


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## Jacck (Dec 24, 2017)

aleazk said:


> Quantum fields are matter. I define matter as any thing that can carry energy. Quantum fields carry energy, therefore are matter. My work is indeed done using quantum fields. At the level of classical fields, you can define spacetime in a straightforward way. At the level of the quantized gravitational field, so far I have been able only to define space. I'm working on an idea for time, but so far is only an idea.


but time and energy do not commute (there is Heisenberg uncertainty relation between them) analogous to the wave/particle duality. So maybe time and energy are different aspects of the same thing.


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## aleazk (Sep 30, 2011)

Jacck said:


> but time and energy do not commute (there is Heisenberg uncertainty relation between them) analogous to the wave/particle duality. So maybe time and energy are different aspects of the same thing.


I didn't say it had to have a defined energy value, but just the property of being able to carry energy. Anyway, the energy-time uncertainty relations are not even true uncertainty relations because time is not an operator in standard quantum mechanics, but just an external real parameter with zero dispersion. There's an atempt by Pauli to define a time operator to make those relations true, but is unsatisfactory. Finally, well, time and energy are indeed related, since, in a Hamiltonian formulation, the energy, i.e., the Hamiltonian of the system, generates the time translation of states in phase space.


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## Sad Al (Feb 27, 2020)

Jacck said:


> matter does not exist, there are only quantum fields with their creation and annihilation operators.


You mean that quantum fields are ontologically real but matter isn't? My understanding is that Einstein thought that space is ontologically real but quantum fields aren't?


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## aleazk (Sep 30, 2011)

Fields are the only ontologically real things. And they are matter as per the definition of the term I gave before. Particles are just quanta of the fields and cannot be taken as ontologically real since their existence depends on the choice of a coordinate system: you can have zero particles in an inertial frame but a thermal bath of particles in an accelerated one, this is called the Unruh effect.


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## Sad Al (Feb 27, 2020)

aleazk said:


> Fields are the only ontologically real things. And they are matter as per the definition of the term I gave before. Particles are just quanta of the fields and cannot be taken as ontologically real since their existence depends on the choice of a coordinate system: you can have zero particles in an inertial frame but a thermal bath of particles in an accelerated one, this is called the Unruh effect.


FNo, fields are not ontologically real. Quote: "what Maxwell's equations actually describe are fields of operators on Hilbert space. Those operators are quantum fields, which most people agree are not real but merely spectacularly successful calculational devices"

http://www.ehu.eus/aitor/irakas/mes/Reference/mermin.pdf


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## aleazk (Sep 30, 2011)

Sad Al said:


> FNo, fields are not ontologically real. Quote: "what Maxwell's equations actually describe are fields of operators on Hilbert space. Those operators are quantum fields, which most people agree are not real but merely spectacularly successful calculational devices"
> 
> http://www.ehu.eus/aitor/irakas/mes/Reference/mermin.pdf


That's just a common opinion you hear from some physicists from time to time. But it's not backed by a serious ontological analysis, just vague intuitions that, ultimately, don't actually imply what they think when made more precise. In general, they are based on the wrong idea that somehow quantum physics destroyed realism. Check this book* for the basics of semantic and ontological analysis of physical theories, and of quantum physics in particular (note that this book is not about the so-called "interpretations" of qm, but about the basic philosophical tools and analysis that you need to do before even trying to make such interpretations; most of them cannot pass the most basic filter of having a consistent semantics... not even to mention the hand wavy declamations like "quantum fields are mere calculational devices".)

*I'm sure the pdf is somewhere on the internet.


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## Luchesi (Mar 15, 2013)

I wish we as humans could experience the proposed higher dimensions, the Calabi Yau shapes and the hidden vibrational (spin) states all around us - and of all that Dark Matter that's out there. We can only develop the mathematical concepts, abstract and seemingly very incomplete.


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## philoctetes (Jun 15, 2017)

aleazk said:


> That's just a common opinion you hear from some physicists from time to time. But it's not backed by a serious ontological analysis, just vague intuitions that, ultimately, don't actually imply what they think when made more precise. In general, they are based on the wrong idea that somehow quantum physics destroyed realism. Check this book* for the basics of semantic and ontological analysis of physical theories, and of quantum physics in particular (note that this book is not about the so-called "interpretations" of qm, but about the basic philosophical tools and analysis that you need to do before even trying to make such interpretations; most of them cannot pass the most basic filter of having a consistent semantics... not even to mention the hand wavy declamations like "quantum fields are mere calculational devices".)
> 
> *I'm sure the pdf is somewhere on the internet.


I'm surprised you would dismiss Mermin so casually... I like the section where he reminds us that all we're trying to do is calculate dynamic trajectories of the things most people call matter..


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## aleazk (Sep 30, 2011)

philoctetes said:


> I'm surprised you would dismiss Mermin so casually... I like the section where he reminds us that all we're trying to do is calculate dynamic trajectories of the things most people call matter..


A casual statement doesn't need more than that to dismiss it... it's really a vacuous statement, since a physical theory is much more than just a calculational tool. To explain semantics and ontology of physical theories would require a book, you cannot pretend I'm going to do that here. Of course, one liners like the one by Mermin (he's not the first I heard saying that) are much more easy to state, understand, and propagate


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## Luchesi (Mar 15, 2013)

"In a new study, scientists fired beams of muon neutrinos and antineutrinos from the J-PARC facility at Tokai, Japan. They identified how many electron neutrinos and antineutrinos arrived at the Super-Kamiokande detector 295km away.
Scientists also observed differences in the ways that neutrinosor antineutrinos changed the flavor. They ended up discovering that neutrinos more likely to change than antineutrinos."


This is suspected to be why more matter than antimatter survived in the early universe.


https://www.techexplorist.com/neutrinos-explain-universe-exists/31674/


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