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Thought experiments in science

Are thought experiments nothing more than verbal arguments in disguise, or do they have a different status and come close in their persuasiveness to actual experiments?

Sir Isaac Newton
Sir Isaac Newton

Dr. Marius Cohen Galileo

Titus Lucretius (Lucretius) Crocus was a Roman poet and philosopher who lived in the first century BC. In his work "On the Nature of Things" he tried to prove the infinity of space through this thought experiment: suppose space has a limit. If someone approaches this border and throws a spear at him, then either the spear will cross what we mistakenly thought was the border and thus we will be proven wrong, or the spear will recoil back. However, in order for the spear to recoil, some body (a wall, for example) must stand in its way, and since this body needs to be located beyond the border, then again it is not a real border to the space.

We do not want to discuss here the validity of Lucretius's argument, but to show how thought experiments, which are often identified with modern physics, accompany us throughout the history of human reason. The ability to conceive a thought experiment is a by-product of our ability to predict the results of a possible action based on our knowledge of the world. We use our imagination and our understanding of how the world works to hypothesize the possible outcomes of an experiment, which we are usually unable or unwilling to actually perform. It was clear to Lucretius that it was not possible to go as far as a place that might be considered the limit of space, but this did not prevent the philosopher from speculating what would happen if someone succeeded in doing so.

In the modern era, there are many thinkers and scientists who proposed thought experiments, the most famous of which are: Galileo Galilei, Isaac Newton, James Clerk Maxwell, Albert Einstein and Ernst Mach. The purpose of these imaginary experiments is often to convince of the truth or falsity of a principle or theory, and many of them have become classics of modern science.

But what is the epistemological and scientific status of thought experiments? Some argue that such experiments are nothing more than ordinary arguments that use figurative language, while others believe that thought experiments have a special status and are different from verbal arguments, and have a persuasive ability approaching that of ordinary, actual laboratory experiments. So that we can discuss the different positions regarding the status of thought experiments in science, we will review two of the most famous thought experiments (without discussing their validity).

Galileo vs. Aristotle

Aristotle, the great philosopher from the fourth century BC, claimed that the heavier a body is, the faster it falls. Almost two thousand years later, Galileo Galilei, the pioneer of modern science, showed that all bodies fall with a uniform acceleration, regardless of their body weight, and this on the condition that the resistance of the medium in which they move is negligible.

Galileo was the first naturalist to apply empirical and mathematical methods in his studies, but he also devised thought experiments, including a thought experiment whose purpose was to disprove Aristotle's statement about falling bodies: Suppose Aristotle is right, and when two bodies of different weights are dropped together, the heavier body falls faster . We can ask: what will happen if we attach the two bodies and create one big body from them? On the one hand, the entire system is heavier than the heavy body alone, and therefore it should fall faster than it; And on the other hand, the light body, which should fall more slowly than the heavy body, will delay the fall of the heavy body somewhat, and therefore the (heavier) system will actually fall more slowly than the heavy body alone.

Since Aristotle's assumption that the heavier a body is, the faster it falls leads to a contradiction, we have no choice, argued Galileo, but to reject it and replace it with the assumption that the speed of the fall of bodies does not depend on their weight.

Einstein made a real contribution to the development of quantum theory at the beginning of the 20th century, but his far-reaching conclusions regarding the nature of reality aroused opposition in him, since, among other things, these surprising things are implied in it:
1. At the microscopic level, nature is not deterministic: physical state A may develop into physical state B1 or another physical state B2 under exactly the same conditions.
2. There are pairs of sizes that cannot be precisely defined together for a given body. So, for example, if we measure the exact speed of a particle, its exact location will not be defined, and if we measure its exact location, it will be its speed that will not be defined (and not due to measurement limitations, but due to an essential property of nature, called the uncertainty principle). The type of measurement is the one that determines which of the attributes receives a precise value and which remains undefined.

Albert Einstein, Boris Podolsky (Podolsky) and Nathan Rosen (Rosen) conceived in the 30s a thought experiment that was supposed to disprove these conclusions of quantum theory (after its publication the thought experiment was called "EPR", as the initials of the names of these physicists) , and here is a simplified version of it: conservation laws allow us to send two particles in opposite directions, so that the two must be correlated in certain properties (for example, in their speeds) even when they are far apart. However, if these properties will not be defined until they are measured and will be determined randomly during the measurement (when the measurements are carried out on both particles at the same time), then having a correlation between the properties of the particles means transferring information between them at a speed higher than the speed of light, which according to the theory of relativity is not possible.

The physicists' conclusion was that the values ​​of the correlated properties are determined at the stage when there was an interaction between the particles, before they were separated and moved away from each other, even if the theory does not allow us to know these values ​​until the measurement itself. In other words, the quantum theory is not a complete theory: non-determinism and uncertainty are not in nature but arise from the fact that the theory does not provide us with all the information about what is happening in the microscopic world.

Later it was proved that Einstein, Podolsky and Rosen were wrong, and that the properties of the two particles are indeed determined randomly during the measurement despite the correlation between them. Although information is not transmitted between the particles at a speed higher than the speed of light, quantum theory reveals another peculiarity of reality: particles may be related in their properties over great distances (theoretically unlimited) without any information passing between them (a phenomenon known as non-locality).

So what is a thought experiment?

It is no coincidence that the two thought experiments described were designed to refute existing paradigms. Many thought experiments are used to challenge existing principles or theories by showing (or trying to show) how absurd conclusions can be drawn from these principles or theories. Sometimes such thought experiments turn over time into laboratory experiments, the empirical results of which confirm or refute the conclusion of the thought experiment, and sometimes, in the absence of appropriate technology to actually perform the experiment, the thought experiment remains a subject of theoretical discussion between its followers and opponents.

One of the main questions regarding the use of thought experiments is the question of whether it is possible to learn something new about the world from them. It is customary to divide our knowledge into a priori knowledge, which does not depend on our knowledge of the world, such as mathematical, logical or analytical knowledge (such as that which arises from definitions), and a posteriori (or empirical) knowledge, which is acquired through observations of the world.

Where should thought experiments be placed? On the one hand, the thought experiment relies on our knowledge of the world, that is, on empirical findings; But on the other hand, his conclusions are accepted a priori, that is, without the experiment actually being carried out. It seems that logical steps performed on empirical data can indeed give us new information about the world, even though this information was obtained a priori, and a good example of this is the concept of alibi: if there is evidence that the suspect in a crime was present in a place far from the scene of the incident when it occurred, we conclude , based on the assumption that a person cannot be present in two different places at the same time, that the suspect did not participate in the commission of the crime. The alibi enables an a priori logical course, the conclusion of which provides new information about the world, information that in principle could also be obtained empirically (through a witness who was present at the event itself, for example).

Another important question regarding the nature of the thought experiments is the question of whether they have a unique epistemological status, or whether they are nothing more than ordinary arguments in "disguise", which use figurative language. The American philosopher John Norton (Norton), for example, believes that thought experiments are no different from ordinary arguments that include assumptions, a logical course and a conclusion, even if their special way of presentation has some psychological benefit. The well-known Austrian physicist and philosopher Ernst Mach, on the other hand, argued that thought experiments rely on "instinctive knowledge" based on experience, and such knowledge is not always possible to fully verbalize. Either way, the beauty of the thought experiments that adorn modern science and the refreshing perspectives they offer in our efforts to understand the world cannot be denied.

A thought experiment for dessert

Simon Stebin's thought experiment. Illustration: From Galileo
Simon Stebin's thought experiment. Illustration: From Galileo

The thought experiment below that Mach particularly liked was devised by Simon Stevin, a Flemish mathematician and engineer between the 16th and 17th centuries. Look at the array of balls, arranged at equal distances from each other, in Figure 3, and try to guess which way the string of balls placed on the slopes of the triangular device will slide.
Since the string of balls added to the original array is symmetrical, it does not affect the movement of the original string. So if the original string slides in any direction, the whole chain will also move in that direction. But since the movement of the chain in any direction will not change the structure of the experimental set-up, there is no escaping the conclusion that if the chain starts to move, it will create a perpetual motion (leading performance). This absurd conclusion obliges us to conclude that the string in Figure 3 is in equilibrium.

For further reading: Worm, Aryeh, Rationality and Progress in Science, Broadcasting University, Ministry of Defense (2004).

Dr. Marius Cohen teaches philosophy at Ben-Gurion University.

The full article was published in Galileo magazine, July 2010

63 תגובות

  1. Luca

    Scientists now claim that the universe consists of 74% dark energy and 22% dark mass, the rest consists of baryonic matter.
    Assuming that the universe consists of all this, then the universe should be 'fenced' in matter and energy of these types.
    Assuming that this is really so, then there is no escape from thinking that the universe has limits. That is, the universe is not an infinite space as it is commonly thought but (as I think) - the universe has limits and is finite.
    Besides, the infinite and flat/open space (according to Einstein) of the universe cannot be measured in any way, unless the boundaries are defined and finite and then they can be calculated.

  2. Hello Luca, get Daim back.

    First, apologetically, a bit of petty precision: the dark matter and dark energy that are being talked about today are not the same thing.

    We learn about dark matter from the fact that the gravitation inside galaxies is greater than we would expect from measuring the amount of visible matter. This is manifested in the fact that the matter inside the galaxy does not escape from it despite the high rotation speed, movement of bodies occurs at a greater speed than expected (even within our solar system), gravitational dusting (the effect of gravity on the movement of light) is strong precisely in the empty regions of galaxies and perhaps more observations.

    We learn about dark energy from the fact that the matter in the universe spreads with increasing speed, that is, there is acceleration. The combination between mass and acceleration, according to known physical formulas, is explained by the existence of energy. The origin of this energy is still unknown, so we call it "darkness".

    Second, your approach is very beautiful and definitely correct. The universe is big and we only see a little of it. If it is infinite, then the entire sphere with a radius of 14 billion light years observed by us is nothing but zero at its end. And if the universe is finite, then we haven't discovered its end yet. Either way, it is possible that beyond the horizon there are hidden things that we do not know, the existence of which may solve the mysteries.

  3. Interesting post and learned comments.

    I want to contribute my cent to the discussion: a particularly wild hypothesis..

    Maybe the dark matter / energy is actually the space itself?
    Maybe the space is made up of some kind of material / mass / energy / something that completes the picture, as energy is actually mass in a different way and vice versa. Why wouldn't the space itself be constructed of a kind of mass/energy?

    If we've learned anything from physics so far, it's that you shouldn't accept things that seem self-evident - as self-evident.
    Casimir showed that even in a complete vacuum there is energy.

    Einstein showed the equivalence of mass and energy, and the equivalence between a gravitational field and accelerated motion.

    Since the universe is actually full of dark energy/dark matter, and no one has yet found even a hint of what these matter/energy look like, what their properties are, what they are made of, etc...why not take a look at what actually surrounds us from all sides - space itself? He makes a big stop, and who knows what other secrets he will hide.

  4. And a small correction: you are indeed the grandson of the founder, but I am rather a great-grandson

  5. Hello debaters,
    Those who understand it claim that it is forbidden to deal with Kabbalah (because according to them it is dangerous and foretells fates) except for people who are really great in Torah. According to the same logic, in my humble opinion, in order to search for answers to new problems and theories and succeed in doing so, one must first understand the existing theories and their weaknesses and deviations, otherwise inaccurate, unfounded and incorrect things are said. After that, you have to ask the right questions, (and here lies a significant part of the solution or at least the right way to find it if it exists) and finally you have to think like geniuses think - that is, outside the box. My advice to the grandson of one of the founders of the Romema neighborhood in Jerusalem, continue to study physics, delve into the subject, and only after you understand it in its entirety - look for a solution to the problems it overwhelms. I don't want to loosen your hands, but the statistics say that the revolutionary theories were published by scientists in their twenties and thirties. Best regards and good luck.

  6. To Bijumbom, 54:
    Could you please elaborate? From the laconic wording it is not clear to me what you do not understand.

  7. Machel
    '…all we have to do is make sure the ends of the chain are exactly the same height.'
    Say something about 'quantum entanglement' of, say, information? Or in the Konti world it doesn't work like that?

  8. Yesterday I received the new issue of Galileo in which the things I wrote in response 27 here were published.
    Next to my response, there appeared a very insightful response from David Agmon From Haifa and I find it appropriate to quote here the part of the response that I really liked.
    a quote:
    If we want to stabilize a uniform chain in a uniform gravity field over some curved surface (and not necessarily a right triangle) all we have to do is make sure that the ends of the chain are exactly at the same height.
    It should be emphasized that this is a smooth surface located in a uniform gravity field and that the equilibrium shown in the diagram is a loose equilibrium.
    By the way, the problem of the combined tools is a "Siamese twin" of this problem; There, too, the surface of the liquid stabilizes at the same height, but in this problem the equilibrium is stable.

    End of quote.
    In his words, he refers to the diagram he attached, but it is easy to understand things even without the diagram (which is just an example).
    Indeed - the conclusion of Stebin's consideration is not limited to the shape of a triangle - it is true for any shape.
    This can also be proven analytically, but I will spare myself the presentation of the proof - unless someone really wants to see it and asks very nicely.

  9. To Yuval (the anonymous from response 51):

    First of all: if to solve one problem you make additional assumptions, you need to explain them as well. If the number of new assumptions is greater than the number of solved problems, that's a problem.

    My drawer got all the physics (that was known at the time) plus a little something original of mine.

    What I offer is an attempt at a solution. Finding similarities between the model in the drawer and the dark matter, I pulled it out. It is clear to me that this model is far from complete, mainly because it does not explain many other things that have been discovered since then.

    Dark matter and dark energy are, according to what is now believed, two different things. But maybe things will change, and there have been things before.

    Someone here was wrong, and I'm almost absolutely certain* that someone is me. I will repeat what I said in one of my earlier comments here: if I don't try, I won't make a mistake. But I won't get anywhere either.
    (* I say "almost completely" not because I'm looking for some glimmer of hope to show some superiority over the person I'm talking to but because I'm almost never sure of anything)

    You offered an explanation that is an attempt to solve the question. With your permission, let's not waste time on semantics.

    If we start messing with what can confuse me we will never finish.

    I retire now to sleep. If you contact me now, I will answer you only tomorrow. Good night.

  10. jubilee
    First of all, what is this sentence supposed to express: 'And if so, do they solve more than they raise new questions?' ?

    There is not much to delve into what you have already told, because what you have told can also be told in other ways, the point is that the idea was known to people even before your drawer knew about it.
    Baside that
    What you offer is a solution and not confirmation or refutation of dark matter.
    You propose such a solution: dark matter and dark energy are one thing.
    But you say that there are proofs in mathematics. In science there are refutations and confirmations. What I write does not fall into one of these categories.'
    And 'my hypotheses do not pretend to solve things but come to offer an explanation'.
    Someone here was wrong and it wasn't me.
    Besides 2
    If you re-read what I wrote, you will understand that on second thought I did not present a solution, but presented an explanation.
    Can it confuse you?

  11. To 48:
    What are you running straight into wormholes? 🙁 There is a lot to delve into what I have already told 🙂

  12. Yehuda: Of all my teachers I was educated - if I had enough sense 🙂

    For commenter 46:
    Let's try to check why you don't think anyone will take what you said seriously.
    Do you yourself believe that these things are true?
    And if so, do they solve more than they raise new questions?

    I actually look at what you wrote with sympathy. The only (really only) reason why I can't relate to her at the moment is the fatigue I've accumulated from this morning until this late hour. Even if you tell me you were just joking, I will look at her sympathetically.
    But now I have a question for you: you said "I don't understand why I would waste time on this". If you have something better to do with your time, wouldn't you?

    There are proofs in mathematics. In science there are refutations and confirmations. What I write does not fall into one of these categories. My hypotheses do not pretend to solve things, but come to offer an explanation (which I know is lame on seven legs) in the hope that someone smarter and more creative than me (or just lucky - maybe you) will come up with something more successful.

  13. jubilee
    If you also add lighting, from above on the tray, then you will be able to see the shadow of the marble as a 'wormhole' through which the information of the marble passes to another place in the space of the tray 🙂

  14. To the owner of response 39, with apologies. I answered casually and in a dismissive tone, but I did not intend to do so. I will answer you now with some "drag and paste" from the things I wrote in a drawer 40 years ago.

    Take a tray (it's enough to do it in imagination) and put a lot of marbles on it. Allow the marbles to move spontaneously within the tray. Note the following important thing: when a marble moves from one place to another, the empty space that was in the second place disappears (because the marble took its place) but appears in the first place (because the marble that was there went to another place). But it's not just as if two tenants changed apartments. The way the sphere moves is not the same as the way empty space moves. The sphere moved in continuous motion while the empty space shrank in one place until it disappeared while appearing in another place and starting to grow. If you will, it is a metaphor for matter and energy.

  15. Yuval, I also trust the physicists to find a way and I also have hypotheses. Here is one:
    After there was more matter than antimatter left in our universe, the antimatter decayed into other particles (which are antiparticles and particles different from the original antimatter and different from existing matter).
    And those particles are the ones that make up the nucleus of dark matter and dark energy.
    But it doesn't seem to me that anyone will take it seriously, and that's why I don't understand why I would waste time on it, it's better not to write, and that's what I would suggest to you and to some others who want to write one hypothesis or another without having proof.

  16. To Yuval Chaikin
    Indeed, maybe my high school teacher was exaggerating a bit, and instead of throwing I should have used the word change.
    I wonder where he is today?
    Good health, dear teacher!
    And happy new year
    Sabdarmish Yehuda

  17. To Judah (response 40):

    Your words reminded Michael and me of the annoyingly boring debate between Darwinists and creationists. In general, scientific criticism has additional tools. One of them is the one Michael mentioned (in response 34) - Ockham's Razor. This principle is accepted not only in science but in many other areas of thought. It can be contradicted in some cases (like, for example, when a judge in a court of law has to decide between a simple picture revealed by the testimony of witnesses and the possibility that the witnesses are all false witnesses hired by an interested party to bias the law), but for the most part it is valid. The phlogiston was abandoned not because it does not explain correctly but because a simple explanation was found from it (Ockham) which also fits well with explanations for other phenomena (efficiency). In my opinion, Ockham's Razor should be discussed in detail. Perhaps one of the regular writers of the scientist should dedicate a series of articles to him, even though it is possible that he will only convince the convinced (and I am included). Until then we will have to make do with Wikipedia.

    But in one thing I completely agree with you: in science nothing is sacred, not even Ockham's Razor.
    Have a good week and a successful year of fruitful discussions.

    To Michael (response 41):
    You can probably make a good guess as to how old I am, if 40 years ago I was kicked out of high school for being a nonconformist.
    I gave myself a second chance and today, at my advanced age, I wear the university benches again. You won't be able to guess where. In the exact place where Kelvin discovered the absolute zero, in the very same building, I'm looking for myself with the clear knowledge that I won't find anything 🙂

  18. Have a good week and a happy new year to you too, Yehuda, and thank you again for the encouragement ♥

    "Throw" is a somewhat harsh response. No? The subtle response is to "expand" the model. When it became clear that certain phenomena were not in line with Newton's laws, they did not "throw away" his theory but expanded it. They added parameters to it and got the theory of relativity. At short distances, at low masses and in slow motion, the theory of relativity is really Newton's theory. Newton did not have the results of the scientists' observations at the end of the 19th century. But if they had, it is possible that Einstein would have remained anonymous.

    Einstein discovered (and one might even dare to say that he discovered by chance) the parameters that you added to Newton's laws allow phenomena to be calculated with greater precision. Today it is evident that the theory of relativity also needs expansion. In the meantime, it is called "dark matter" because not much is known about it except that it is involved in two types of processes (Michael claims, with some justice - if we stick to the theory of relativity, because they show years of the same thing): gravity and gravitational repulsion. A good model that explains simply (Ockham's razor) and efficiently (allows for more accurate calculations) the new observations will, obviously, replace the theory of relativity. As you and I know the sociology of science, most probably the exchange will be done by adding parameters to the equations - as usual.

    To the one who forgot to identify himself, thank you too.

    It's not clear to me either how both can be one thing, but I trust the physicists that they will already find a way.

  19. The discussion here illustrates the difference between creationists' poor understanding of the theory of evolution and what evolution actually is.
    The chances that any combination of words will connect to a correct theory is zero, but when each time the incorrect words are eliminated and the correct words are left, the cumulative selection creates a plausible theory.
    This type of selection makes evolution non-random even though the mutations are completely random.

  20. jubilee:
    Now (37) you are talking about something completely different.
    It makes sense and in fact I have already proposed a theory about this to several physicists.
    It's more complex than you describe but it seems to me something that makes sense.

  21. Dear Yuval Chaikin
    Certainly mass and dark energy, both, are the same thing, and I'll explain why.
    Because dark energy is negative dark mass!!!, only they don't call it that. But if dark mass has gravity then negative dark mass has….that's right, repulsion!
    So why is it still called dark energy???
    Because apparently it has a historical background.
    There used to be a cute theory called the phlogiston theory. She tried to explain how bodies heat up and that's why a special liquid called phlogiston flows into them and if the body cools then the phlogiston escapes but what happened, once someone took rust and heated it and iron was formed meaning phlogiston entered the rust upon heating and iron was formed. But what to do and the iron with phlogiston weighs less than the rust?, the solution: - phlogiston has a negative mass!!.
    And very quickly, this was the first step in giving up the expensive phlogiston.
    You realize that declaring something as negative mass would be the beginning of the end of something
    Therefore, since Newton's formula is sacred (did we say it already?) then it is not called negative dark mass, but rather the beautiful name - dark energy!
    But believe me Yuval Chaikin, like it or not, this is the beginning of the end of both dark mass and dark energy
    Good Day
    Sabdarmish Yehuda

  22. Look, Yuval, 'energy' in the sense of 'dark energy' is actually 'motion'. That is, the process of something.
    And this movement cannot be carried out without having a mass - which the force/energy will move.
    It may be that this mass is embodied as 'dark matter' and it may not be, it is still not clear to me how 'both can be one thing', especially when one does not respond to anything except gravity and the other responds to everything except gravity?!

  23. To Yuval Chaikin
    Keep asking because this is the way.
    Don't take anything for granted.
    The dark matter theory can only exist with dark energy because the universe is accelerating despite the dark matter that is supposed to slow it down and cause it to collapse.
    What is happening here is that there is a sacred formula - Newton's gravitation formula, and when the results of the measurements do not match it then... the measurements are changed! How?, with the help of a dark substance that we don't know what it is, or if that doesn't fit either, then we add dark energy that is created from the void (?) that we also don't know what it is.
    I was taught in high school that if measurements do not fit the formula then it is necessary to throw out the formula and not change the measurements. But what to do, Newton's gravitation formula is a sacred formula (did I say it already?) and will never throw it away.
    And you have to throw it away and how you have to throw it away. It is not possible that results will not match ten times a hundred times or even ten thousand times and Adin will stick to the formula almost like a member of Knesset sticks to his chair.
    Good week Yuval
    And a good year for everyone
    Please respond gently
    Sabdarmish Yehuda

  24. Today we talk about dark matter and dark energy as two different things. However, as they found that mass and energy are the same or that the curvature of space and the force of attraction between two bodies are the same, it is not impossible that it will turn out that dark matter and dark energy are different aspects of the same thing. After all, everything is fluid and we still don't know where we stand.

  25. Yuval, maybe you got confused, did you mean dark matter and dark energy when you wrote 'two types of dark matter'?

  26. To Michael,

    Right. The explanations I'm trying to give must be very lame. But the questions are still there and burning.

  27. jubilee:
    Dark matter creates only the effects that mass creates (curvature of space - according to Einstein and gravitation in the spoken language).
    He doesn't do anything else so there is only one thing here.
    On the other hand, he explains many findings, mainly the rotation speed of stars in galaxies (which many times, in fact most of the time, do not coincide with the visible matter) and gravitational recirculation around regions where there is no visible mass.
    I assume you know that the smaller a number of assumptions give an explanation for a larger number of phenomena - the more the Torah is considered superior (according to Ockham's Razor).
    It is not clear to me what two unrelated phenomena you are talking about.
    The term "two dark substances" doesn't match anything for me either.
    No one had ever thought about dark matter before its gravitational effects were discovered.
    I did not find in your words an explanation for any inexplicable phenomenon and all I see in them is an unnecessary addition of assumptions that even spoils some of the existing explanations (for example - dark matter does not exist everywhere and the attempt to link it with EPR-like phenomena - which occur everywhere - is completely illogical).

  28. Thanks to Michael and Zvi.

    Unfortunately, my curiosity was not satisfied. We know about dark matter because it participates in gravitational processes. It even led thinkers to conclude that dark matter has mass, simply because until now gravitation has been attributed to mass. At first I also accepted it with satisfaction, but pretty quickly I had doubts. The results of the famous experiment conducted by Eddington to confirm a certain conclusion of the theory of general relativity convinced the world of physics that the trajectory of electromagnetic radiation (visible light, in that experiment) is affected by the presence of a massive body, which was known as the "curvature of space". In the meantime, we discovered this phenomenon in distant galaxies and thought that this effect cannot be attributed only to visible bodies, and hence that in addition to the dark matter that interferes in gravitational processes, there is also dark matter that interferes in optical processes. One of the questions that immediately arose in this context is whether the two dark substances are the same. Michael wrote "the only thing that is actually measured in relation to dark matter is its mass" and the theory of relativity attributes the gravitational decay to the mass, and hence the answer to my question is almost immediate - yes.

    But I have other birds hatching in my head. I want to understand the essence and form of operation of the mechanism that causes mass to curve space. I thought to Tommy that instead of stating that mass causes two different phenomena that are seemingly unrelated to each other, it might be better to assume that there is something else that is distributed in the space of the universe in an inhomogeneous manner and that different densities of it create different phenomena. The degree of curvature of the light's path is a function of the degree of density of this something; Density above a certain threshold creates subatomic particles and greater density creates larger structures up to black holes. I came up with this hypothesis, as mentioned, about forty years ago and buried it in a drawer, but following the massive preoccupation with dark matter that began a few years ago, I returned to it.

    The Michaelson Morley experiment did not confirm the existence of the site. Hendrick Lorenz proposed an explanation according to which the ether exists but the experiment did not reveal it because bodies contract in the direction of their motion. Einstein completely ignored the ether, but his theory of relativity shows that bodies do contract exactly as Lorentz proposed. For me, the layman (only second year physics, for now), I have no problem accepting the various determinations of my teachers and gentlemen, but I still do not feel comfortable in the face of the multitude of assumptions. Today, when it turns out that the empty space is not empty at all but full and overflowing with dark matter, I am again looking for the medium in which the electromagnetic radiation moves in the dark matter. In light of the refutation of the "EPR" thought experiment, I am also looking for the possibility of the existence of movement at a speed greater than what is considered today as the upper limit of speeds. I talked about latitudinal waves and longitudinal waves only because it is known that longitudinal waves are faster than latitudinal waves. I do not insist on this, but the birds continue to peck at my brain with tireless vigor.

    In short, in my defense I will claim that I am not inventing new laws of physics but rather trying to find an acceptable explanation for the existing phenomena.

  29. To Yuval,

    In your response (6) you mentioned the invention of a longitudinal component to light as a possibility that might explain things.

    For many years it was not known what the nature of light was, until at the end of the 19th century Maxwell developed the four equations named after him, which describe the electromagnetic field in a complete way. From these equations, a prediction emerged for the possibility of the spread of electromagnetic waves which had, among other things, two significant properties:
    - The waves were expected to move in a vacuum at the speed of light
    - The waves were expected to be transverse waves only (the magnetic and electric fields are perpendicular to each other and also perpendicular to the direction of movement).
    These two properties corresponded to what was observed about the light and therefore it was suspected that the light is actually electromagnetic radiation, a conclusion that was confirmed a few years later (by Hertz).

    from this,
    There is no reason to discuss the possibility that light has a transverse component - there is no reason to think that it exists and in fact it contradicts things that so far we do not find any reason to contradict them (Maxwell's equations and with them special relativity).

    As for the idea that dark matter is the medium in which light waves propagate, it is already clear from Michelson Morley's experiments that light does not move in any medium and in this respect dark matter has no advantage over ether.

  30. jubilee:
    I'm not trying to kill anyone unless they show disdain for others (such as inventing physics without knowing physics or disdain for scientists or blatant lies and the like).
    Your last question does not include any of these and I have no problem answering it with ease.

    When you talk about "bodies made of dark matter" you are talking about something different than what you think.
    According to the assumption - dark matter does not maintain (or almost does not maintain) non-gravitational interactions.
    This means that he cannot create bodies in the conventional sense of the word. Therefore - apparently - there are no bodies made of dark matter just as there are no bodies made of neutrino particles.
    You can ask - therefore - only about particles of dark matter (assuming it is made of particles - which is not obvious) - or about entire galaxies.
    Dark matter particles have not yet been found and it is not at all certain if there is a way to find them.
    The masses of galaxies (which are mostly dark matter) have actually been measured (including galaxies that are made of dark matter almost exclusively).
    I say again: if dark matter did not have results that the only thing known to us that can cause them is mass - no physicist would believe in its existence!

    In relation to photons - it has been proven that there is an attraction between them and other masses.
    In general - it has been proven in experiments that energy has mass in the sense that it attracts and pulls gravitationally (the "mass" of the photon is also like this) and that mass and energy become one another (for example - particles created in particle accelerators, nuclear bombs, radioactive decay, etc.).
    I don't know if experiments have been performed that measure the mutual attraction of two photons.

  31. To Michael, please don't be rude. I am just asking. Not trying to be clever.

    I have two questions regarding mass.

    First question: You said "the only thing that is actually measured in relation to dark matter is its mass". Indeed, on the face of it, it is certain that the dark matter is involved in gravitation processes, due to the abnormal behavior of massive bodies in different regions. But you will surely agree with me that no way has yet been found to measure the gravitational pull between two bodies made of dark matter. Can we, in light of the fact that such a phenomenon has not been measured, accept without question that dark matter has mass?

    Second question: You said "that a photon has a mass of motion... this is a fact that has been proven in many experiments". If two photons in motion have mass, then they would be gravitationally attracted to each other. Has this phenomenon been confirmed in any experiment?

    Again: I'm not trying to be clever. As I mentioned before, maybe I don't know what I'm talking about. I would appreciate an explanation or a link to them.

  32. To Michael.

    I feel bad for making you feel guilty. That was not my intention, and I apologize for giving this example.

    I thank you for your consideration of my words, even though we do not see things eye to eye. And maybe we just don't understand each other, and maybe I really don't know what I'm talking about.

    As a rule, I am on the side of the questioner and not the answerer. Only when there is no clear answer do I speculate and am happy to receive confirmations as well as refutations.


  33. The response I sent to Galileo:

    I would like to comment on Dr. XXX's response, which dealt with the "Science Seeker" section by Dr. Marius Cohen on thought experiments, and on Marius Cohen's response to this response; All this in issue 145.
    In Stebin's experiment, if at all, only one correction needs to be added, and that is that instead of a rope with balls, there will be a chain (or rope) with a uniform density (mass distribution) (in fact, all that needs to be ensured is that the ratio of the masses placed on the ribs is the same as the ratio between the ribs. A uniform distribution of the mass over the surface of the rope guarantees this, but this is also true in the original drawing. When the ratios are not the same, the assembly will slide in one direction and if the section of the chain below is connected to it, it will enter into a cyclic movement - go to the right and return to the left). When this correction is introduced, the experiment is completely correct and leads to the required conclusion - regardless of the shape of the triangle - provided that its base is placed horizontally.
    The fact that the system will not move immediately can be deduced from the law of sines.
    If we call the sides that are not the base a and b and the angles opposite them are called A and B respectively, then the law of sines gives (after a simple transfer of sides) the equality (a×sin(B)=b×sin(A
    If we mark the density with the letter r, then the force on one side is (r×a×sin(B kilogram-force) and the force on the other side is (r×b×sin(A kilogram-force).
    From the equality it is clear that the two forces are equal.
    This is a proof of the non-displacement of the system in a way that is not related to the paradox. But the paradox claim is also justified (so much so that it led me to think that there is actually a physical proof of the law of sines here - a proof that probably allows one of the axioms of geometry to be omitted and replaced by the axiom "there is no leading perpetuum").
    Why is the paradox statement true? Because in order for the system to start moving, acceleration is necessary. This is not similar to turning a wheel on a frictionless axle, because in such a rotation there is no change in the overall momentum of the system.
    If the system changes the total momentum at the beginning, it will continue to change it and produce kinetic energy that can be harvested.
    Alternatively: if there is a total momentum change at the beginning, a sign that an external force acted on the system. This force is probably greater than zero. In this case, even if there is a little friction in the system (the value of which is less than the force that drives the system), the system will move to infinity - and even accelerate - even though there is friction.

    Stebin's paradox also makes it possible to reach a physical conclusion that is much (much much) more difficult to calculate directly, in an even more complex question:
    Suppose the triangle is mounted on a rail that allows it to slide without friction left and right. Will the system move in this case?
    The forces acting here are much more difficult to calculate, but the consideration of the Stebin paradox inevitably leads us to the conclusion that even then the system will not move.

  34. jubilee:
    You don't want to get into the section of scumbags, so you go into the section of scumbags and others that don't belong to the matter.
    Indeed, I help my father here and there - among other things by releasing comments that were unjustly stuck due to the site's automatic filtering mechanism. Do I have to apologize for that? Does anyone need one? Would you prefer your comment to remain unapproved?

    You use the term "dark matter" to describe something completely different from what scientists call dark matter and you call it dark matter only to justify the claim you made forty years ago about what scientists are talking about today.
    Well, the truth of the matter is that you are not talking about the same thing - neither then nor today.

    Regarding the speeds - I actually addressed the matter - see response 7.
    I will also add that I see no reason to attribute to longitudinal waves of an unknown type a speed higher than that of light waves and the fallout from earthquakes seems irrelevant to me.

    And I will add that the transfer of information at a speed exceeding the speed of light will allow - according to the theory of relativity - a situation where an effect precedes its cause. This connection between reason and motive seems to me to be one of the last things that would make sense to give up. As mentioned - the connection between intertwined particles cannot be called information transfer. According to quantum theory, this is information created simultaneously in both particles and there is a law of nature that causes the information created in particle A to match the information created in particle B.

  35. Michael

    It's a bit hard for me to understand from response 10 what connection you're looking for, but the problem can be thought of as follows.
    It is clear from Stabin's paradox that the force on both ends of the chain (top figure) must be equal. Is it possible to show what the nature of the force must be from trigonometric considerations and the paradox? The force on each chain is proportional to its mass and since the chain is made of identical balls at equal distances, the forces are proportional along the length of the chain, that is, along the side of the triangle. What is the constant of proportion? From the theorem of sinonases we learn that the product of the sine of the base angle of the triangle, in the side from which it is constructed (sorry for the lame explanation), is equal to the product of the sine of the second base angle in the other side (it would have been desirable to add a drawing). From the geometric argument we learn that the force acting on each of the ends of the chain is proportional to the sine of the angle at the base of the angled triangle that the same side makes up and thus we got the nature of the force that is usually obtained in a different way.

    The balanced force is usually obtained in a different way in mechanics classes from considerations of the balance of forces when gravitation pulls downward and the normal acts perpendicular to the surface, and from this you get that the force is the mass of the body times the gravitation constant times the sine of the angle. Is that what you meant in your comment?

  36. The comment section I responded to:
    The above reasoning has two problems: First, it is not clear to me why the experimental setup will not change due to the movement of the chain: in fact, from Figure 3 it appears that if it slides a little to the left side then the right side will be heavier because the lower ball moves a little to the right and up and upset the balance. Second, it is wrong to say that eternal motion is an absurd conclusion. Basically, under ideal nominal conditions, i.e. without loss of energy due to friction (as Stabin's experiment probably assumes) this is a very natural conclusion: a wheel rotating on a frictionless axis, a moving pendulum in a frictionless environment, or a ball sliding on a frictionless track in the form of a symmetrical semicircle standing, all will persist in their motion forever.
    In any case, despite the flaws in Stebin's reasoning, his conclusion that the string will not slide in any direction is still correct, and this is under certain assumptions that were not completely clear from the article. The assumptions are that the triangular device is a right triangle whose perpendiculars ratio is 4/3, that there is no friction, and that all balls are identical. If we denote by m the mass of each ball, and by g the acceleration of gravity, then from Figure 1 we get that on the left chain there is a force ( 4m*g*cos(α) to the left, and a force ( 3m*g*sin(α) to the right. These forces are equal because tan(α)=4/3 of the assumption, so the string that started from rest, will persist in its rest.

  37. Hello Michael,

    I didn't mean to enter into a dialogue of catties. Therefore, apologetically, I do not continue to talk about the dark matter - but this should not be seen as a message of "defeat".

    And now I will play the role of a detective, just to demonstrate the way an investigator works. As soon as I sent my response #20, it appeared with the title "Your response is awaiting approval". Because I was afraid that she would be lost (as happened to me once, unfortunately, with a beautiful and troll-free response that I sent to another article here - "The priesthood is not what you thought"), I refreshed the page again and again. And here, suddenly after about 10 minutes, my approved response appeared and your response 21 was attached to it. From the fact that your response is long, I assumed that it took you between 5 and 10 minutes to write it and it is not possible that my response would not have been placed before your eyes while it was hidden from the rest of the science readers. The paranoid in me immediately conjectured from various hypotheses. I assumed, for example, that you are not only a full-fledged reader who responds to the matter, but also that you have moves in the knowledge system and control over the publication of the responses of others. An investigating policeman would stop here and say that there is no doubt that you are a member of the system. A scientist worthy of his name would not stop here but try to put his hypothesis to further tests. I searched the sitemap under team members and did not find your name there. It's a mystery.

    And regarding the first issue I even opened (comments 2 and 6), I did not receive a serious response from you. To remind you: in response 6 I raised the possibility that in addition to the latitudinal waves of light there are also longitudinal waves. Unfortunately, you and others stuck to the concept of "dark matter" that I threw out here and did not address this question which seems to me to be more important.

  38. jubilee:
    On the contrary.
    The only thing that is actually measured about dark matter is its mass retardation.
    They don't know how to measure any other feature of it.
    It is not clear to me what properties you mean in relation to its interaction with radiation - unless you mean the absence of this type of interaction. I wouldn't call it a property any more than I would count the lack of consciousness among the properties of a proton.
    You can call the fact that a photon has a mass of movement by any name you want, but it is a fact that has been proven in many experiments.
    If you plan to rebuild physics - the science site is not the place to do it. Before you address the general public, you must address the scientific community and amplify your words under their criticism. Only after you have passed this test is there room to appeal to the general public.

    It is impossible to refer you to my response in Galileo for two reasons:
    One is that I sent it a few days ago (after reading the response of that lecturer from the Technion) and it will be included - at the earliest - in the next issue. The second is that in any case there is no access to the comments published in Galileo via the Internet.

    The only way before me is to present the response here (after all, I have the text), but I don't want to do it out of context (and the context is, as mentioned, the response to which I am responding).

    I also want to encourage the people to think before I post the things and in response 10 there is a serious hint regarding them.

    It is possible that later I will publish part of the response to which my words refer, to create the context and then - after people think a little more, I will publish my response.

    In the meantime - I suggested that you think (after all, whoever wants to rebuild physics - surely knows the existing physics - otherwise he has nothing to base the claim that it should be replaced).

  39. To Ehud and Michael:

    to like:
    In my opinion, saying "there is no law of conservation of mass, but mass can become energy and there is a law of conservation of energy" is an unsuccessful use of semantics, since the transition from mass to energy is two-way.
    On the other hand, I completely agree with you that "an assumption about a particle for which the concepts of mass and energy do not apply is beyond the language of physics today", with emphasis on "today".

    We still have no explanations for certain phenomena. Sometimes, when explanations are not available, there is no escape from expanding the theory. The trash can is always with me, but I also use it carefully. For example, to reject a metaphysical claim just because it is not limited to the laws of physics is in my view a serious error. And by the way, schizophrenia, a full explanation has not yet been found for it either and the drugs for it are still not effective, but we do not despair.

    Indeed, as long as I do not bring proposals for experiments, my hypotheses have no scientific value. However, here we are not dealing with a scientific experiment, but with thought experiments in science, and that is why I dared to appear here and disturb the peace of the holiday and Rosh Hashanah. I suggest that instead of talking about the dark matter, which in my haste I threw on the stage, we talk about what seems to me more important than the things I said here. To remind you, I was talking about latitudinal waves and longitudinal waves: the electromagnetic radiation we are familiar with appears in latitudinal waves, and these progress more slowly than longitudinal waves. I asked (I didn't determine. I just asked): "Perhaps light also has longitudinal waves and this is where the solution to the mystery lies."

    By the way, thanks for mentioning Zwicky. I will look for and learn about him when I get the chance.

    To Michael:
    "Mass is the only attribute currently attributed to dark matter": indeed, but as of now no way has been found to measure it directly. Dark matter clearly has at least one other property that manifests itself in its interaction with electromagnetic radiation whose carriers are massless (unless we adopt the hypothesis, which is no less strange than my hypotheses, that the photon has "motional mass").

    The particle I came up with is supposed to build physics and not the other way around. Physics is subject to him, but he is not subject to it. Therefore, concepts from the world of physics - such as mass, energy, conservation laws (known today), physical constants, etc. - are not relevant for him.

    It's nice to start the year in a good mood 🙂

    And regarding your response number 10, can I please have a link to your response in Galileo?

  40. And for anyone who wants to return to the ground of reality and is also interested in physics, I repeat and recommend referring to response 10.

  41. It is somewhat reminiscent of the joke in which a listener turns to Radio Yerevan and asks "Is it true that cars are given away for free in the city square in Moscow" and the announcer answers him "Basically it is true but it is not in Moscow but in Petersburg and they don't give away cars but steal bicycles"

  42. jubilee:
    I will just add to Ehud's words as follows:
    Mass is the only property currently attributed to dark matter.
    It's a bit strange to me when you attribute other properties to something, you don't attribute mass to it, and claim it's the same thing.

  43. jubilee

    Some Comments:
    40 years is indeed a significant period of time, but the presence of dark matter was conceived by Zwicky back in 1934.

    In physics there is no law of conservation of mass since mass can become energy according to the famous formula... and therefore it is not conserved. There is a law of conservation of momentum and energy. If what you hypothesized is true, inconsistencies should have been discovered in countless experiments and as far as I know this is not the case.

    An assumption about a particle for which the concepts of mass and energy do not apply is beyond the language of physics today. When you make such a claim, there is no room for discussion between you and a physicist. The basic characteristic according to particle physics is mass and energy. Elementary particles can differ in electric charge, baryonic charge, etc.. but they will all have energy. A hypothesis regarding a particle that does not fulfill this is not within the scope of physics and the assumption that there are particles moving at a speed higher than the speed of light seems a conservative proposition. One of the most important things in science is not only to make hypotheses but also to think of an experiment in which the hypotheses can be tested. To prove his model a scientist must try his best to disprove it. Such a kind of scientific schizophrenia.

    Side note: I don't think there is any room for refuting mere conjectures on the site, if a person takes his words seriously he should try to prove them in the accepted ways otherwise it might be better not to mention them (I am of course expressing my opinion which is probably different from yours).

  44. Hello Ehud, thanks for the Sipa and the Risha.

    Another thing I didn't mention is that I started conceiving my hypotheses about dark matter about 40 years ago (when this concept had not yet been created). I called it the "elementary particle" and hypothesized that if it does exist then it behaves in a way that today is attributed to dark matter. For example, the law of conservation of mass (and energy) does not exist in it, because at the level of its structure there is no mass (or energy). Indeed, today's scientists cannot directly measure physical sizes of this matter, although there is clear evidence that it exists (gravitational dust, black holes, etc.).

    I accept what you say about my hypotheses ("There are two phenomena that we don't understand, maybe they are related?"), although on the face of it I disagree with the specific example you gave. I do not believe that there is any reason to dismiss outright an attempt to link two unclear phenomena which seemingly do not seem to be related. For example, today I believe that mass and energy are two sides of the same thing.

    And yes, certainly, theoretical physics is full of garbage cans to which even your little faithful servant in practice has contributed quite a bit 🙂

  45. jubilee

    In my opinion, there is room for caution in raising hypotheses, or as Einstein put it, "the most important tool for the theoretical physicist is the trash can." Your hypothesis is based on the following rule: there are two phenomena that we do not understand, maybe they are related? An example of this type of explanation can be found in the well-known mathematician Roger Penrose who believes that the problem of free will can be solved using quantum theory. Regarding your hypothesis, what about the law of conservation of energy. It is well known that when light or photon as it is commonly called is emitted, the law of conservation of energy is fulfilled. You claim that a "dark mass" particle is also emitted, what happens to the energy balance. How have they not noticed the missing energy in this emission of photons that the dark particle takes?

    By the way of your saying "We grope in the dark, but every now and then random points of light give us new lines of inquiry." It is excellent in the context of the theory you bring up...

  46. hello anonymous user (12)

    I'm not claiming anything, just speculating.
    When I wrote what you quoted I accidentally left out the word "maybe", and for this comment I thank you.
    I ask that the rest of the things I write, which sound as if they are dogmatic assertions, be treated as mere speculations.

    Today it is known with certainty about the existence of something that is currently known as "dark matter". I'm just trying to guess what this dark matter "looks like".

    In my humble opinion, those who do not hypothesize are not wrong, but neither are they getting anywhere.

  47. Mr. Haikin
    On what basis do you claim that "when an event occurs in which light is emitted, a particle of dark matter is also emitted."?
    And in general, what do you rely on when you claim what you claim in response 11?

  48. To Michael, thank you.

    We grope in the dark, but occasionally random points of light give us new lines of inquiry.

    Many hypotheses are currently brewing about dark matter. Maybe he is the elusive graviton in his own right. When an event occurs in which light is emitted, a particle of dark matter is also emitted. But while the light moves in a transverse wave, the dark particle moves in a longitudinal wave. And by the way, you mentioned the graviton, if it is indeed the particle I'm talking about, then the propagation speed of the gravitational waves is greater than the speed of light and you should look for them in this range.

  49. When the article was published in Galileo - a doctor of mathematics from the Technion commented that the Stebin paradox was wrong.
    What was wrong was precisely that doctor's claim and since the editor's response to his words indicated that I sent them a response explaining what was wrong with his claim (with a suggestion to improve something in the wording of the paradox itself).
    I don't want to publish my response here out of context, but I suggest to those who are interested in the paradox to think about the following question:
    What is the connection between Stabbin's paradox and the law of sines?

  50. For anyone who has read the article - it is recommended to enter it again because a section was added to it that was omitted in the first version.

  51. Thought experiments are part of the way scientists think about science. You can think about science through formulas and understand how a physical system will behave if we change its parameters. Another way is to imagine the system within certain limits. If I'm not mistaken, Einstein as a child thought about thought experiments in which he obtains a beam of light. This type of thought experiment helps the scientist develop his theory. The famous thought experiments are those that allow scientists to compare two theories, for example the EPR experiment whose purpose was to show that quantum theory is an effective theory. Sometimes scientists can argue with each other through thought experiments, for example the debate between Einstein and Bohr. Einstein devised a thought experiment in which he simultaneously measures the energy of a photon and the time in which it is emitted, in such a way that the accuracy of the experiment can exceed the barrier provided by the uncertainty principle. Bohr showed that this type of experiment is not possible, that is, the accuracy of the experiment will not be better than the barrier of uncertainties. This by using general relativity and thereby convinced Einstein of his righteousness. In my opinion, thought experiments are part of the language of science, the way scientists think about science and communicate with each other. Thought experiments do not need to be related to actual experiments, for example you can imagine worlds in which the constants of nature are different, for example Newton's constant of gravitation is zero or infinite.

  52. jubilee:
    I don't see the connection to the dark matter and in general - the term "speed" seems to me to be unrelated to the situation in which it seems as if the "transfer of information" is instantaneous, that is - it does not take time at all.
    Under these assumptions - if we talk about speed at all - then it is infinite speed.
    Be that as it may, to this day no one has found an interpretation of quantum theory that really fits with our intuition and the only thing that seems to really work is its mathematical description.

  53. To Moses:

    First, thank you.

    As Michael Rothschild hastened to answer before me, the experiments show that the decision as to which of the socks is black and which is white is made not when separating them, but as soon as the experimenter decided to capture one of them in his paw.
    Since the result is the same even though the experimenter decides to hunt him for a sock at random times, I (with my limited imagination) am led to understand, obviously, that at every moment of the separation they maintain contact with each other and coordinate how to behave. And if this is indeed the case, then the intermediary between them transmits messages at a speed that exceeds the speed of light.

    As we know, light waves are transverse. From what we learn about phenomena like earthquakes, transverse waves are slower than longitudinal waves. Maybe light also has longitudinal waves and here lies the solution to the mystery.

    Recently we have been hearing about "dark matter" and "dark energy". I would not be surprised if it turns out, for example, that dark matter is the desired medium.

  54. Moshe:
    It's really much more complicated in quantum theory.
    What you described with the socks is an example of hidden local variables - something that has been proven not to be what happens in quantum theory (Bell's theorem and the experiments involved).
    Therefore, there is a "kind of" transfer of information here - but not one that we can make use of because it is not information that we know (and not even one that we can find out before it was transferred).

    The question in the title of the article is interesting and my answer to it is "it depends".
    There are certainly thought experiments that are nothing more than ordinary logical arguments that graphically describe a process of drawing conclusions from a set of agreed-upon assumptions. The thought experiment of falling heavy bodies and light bodies is like this.
    On the other hand - the bucket experiment is not like that.
    What differentiates the two cases is our ability to reach a clear conclusion regarding what should happen.
    In the second case, the experiment does not allow us to reach definitive conclusions about the world, but it can help us clarify the questions that bother us and suggest an experiment that will actually be conducted to find out the answer to them.

  55. Liuval: "The properties of the two particles are indeed determined randomly during the measurement, but a correlation was found between them." How can this be explained if information is not transmitted between the particles at a speed higher than the speed of light?

    This can be explained as follows: Suppose I know that you always have one white and one black sock. If I see that you have a black sock on your right foot, I will immediately know that you have a white sock on your left foot - and there is no need for an information transfer mechanism here. In quantum mechanics it is of course a bit more complicated, but in any case they proved that the mentioned correlation does not allow information to be transferred at a speed higher than the speed of light.

  56. Notes and achievements:
    1) Galileo proposed a number of thought experiments, and most importantly they were all proposed not from Galileo's own mouth. Galileo wrote books of dialogue. For example, a dialogue about two large world systems. The dialogue is between three participants: Aristotle, a friend of the intelligent Galileo and a participant representing Galileo. And the participant representing Galileo offers the thought experiments mostly to demonstrate that the earth moves. or to disprove another Aristotelian thesis. or to advance knowledge. And why dialogue? Because Galileo was subject to the watchful eye of the Church and therefore he could not write: I propose... So he put in the mouth of Salviatus: "Let us imagine..."
    2) Einstein devised Gedanken experiments - hence the expression in modern physics. From Einstein. And it comes from the theory of relativity. The EPR is a late thought experiment of his - and Einstein conceived it back when he was in Germany in 1932. When he arrived in the US he and Podalsky and Rosen wrote the article. In this context it is worth noting the Aspect experiment, Bell's inequality and quantum teleportation.
    3) John Norton is a historian and philosopher of science who currently lives in Pittsburgh. He has a much more complex argument. He wrote about Ernst Mach and Einstein. Therefore, it is not possible to say "on the other hand" and mention Ernst Mach as an equal. Mach is one of the greatest physicists and philosophers from the 19th century - who among other things influenced Einstein on his way to the theory of relativity.
    4) Newton also proposed thought experiments - for example the Hadley experiment.
    In simple language they all went to a thought experiment because in their time it was not possible to realize the experimental situation that they proposed in an experimental arrangement. Or alternatively, there are thought experiments that in principle cannot be realized in the laboratory, but they work according to the laws of physics and do not contradict them.

  57. Questions about the speed of light:

    On what basis is it determined that the speed of light is the upper limit for the speed of movement of any possible particle?

    "The properties of the two particles are indeed determined randomly during the measurement, but a correlation was found between them." How can this be explained if information is not transmitted between the particles at a speed higher than the speed of light?

    They used to talk about particles whose speed is always greater than the speed of light - tachyons. Is there any point in discussing them again?

  58. Very interesting and enlightening article. My opinion is that epistemologists will deal with these definitions, while the empirical researchers in the laboratories will make use of thought experiments, whether the definition is one or another - because these are useful both in understanding and in explanation. There is no debate about their necessity and I will stop there.

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