places at the same time?

Maybe it duplicated itself instead.

Or is that basically the same thing? This always makes me confused when I ask myself this.

(Sorry of I've posted this on the wrong board, but I wasn't really sure whether it should be here or on Science General.)

There are many aspects ot the double slit experiment, but the convincing step seems to be when they slow down the photon emission so that only one photon at a time hits the screen on the other side of the slits. Just one, not two, or more. The dots formed by the photons as they slowly accumulate show an interference pattern. How else could that happen, unless each photon interferes with itself somehow?

I have been away from this for close to 40 years. Some of what I have to say may be quantum-mechanical BS, but here goes.

My inclination is to think of our particle, whether it is a photon, electron or some other subatomic particle, as an intensely concentrated wave of energy whose center passes through one slit but whose rarefied extremities encounter both slits.

If anyone who is up to speed on the mathematics of QED and particle/wave duality thinks I am off base, please speak up. I am here to learn and rediscover, as well as to comment.

Remember that when you use a detector to see which slit the photon goes through you don't get the interference pattern anymore.
If the photon really split into two (or duplicated itself) it should be able to somehow signal its counterpart when it gets detected. The signal should arrive immediately because if both slits have a detector only one of them sees a photon.

BTW this behaviour has no classical analogy. Richard Feynman said that it should not be understood but rather accepted.

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"The cure for boredom is curiosity. There is no cure for curiosity."

Dorothy Parker (?)

I think that it is fairly obvious that light is neither a particle nor a wave, but something we do not have a macro analogy for. (or at least not one that we have used so far). The same may be true for other “particles” such as atoms.

IMO, there is no “solid” matter at all. The sub atomic building blocks of all matter are tight little bundles of energy. It is possible that when energy is divided into a small enough packet, it forms a tight loop, acting like a superconductor. Different sizes of energy packets form different self-sustaining shapes. It is these little packets of energy that are the sub atomic “particles” which form atoms. This might also explain how matter can be “converted” to energy. Perhaps there is no real conversion, but rather merely unraveling of the energy packets which combine to form usable energy.

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Reality: What a concept!……………………..><Ç(((Ç°>

How is it possible for something to be in only one place at a time since there are so many places for it to be? It seems highly unlikely. I'm used to it so I don't constantly question it, but I don't understand it.

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Life is like a box of chocolates. All of your choices are bad for you.

Unlikely? Are you joking? There may be many possible places for some object to be, but the fact that it ends up in just one of those places at any one time seems obvious. It is one thing to be unable to predict exactly where a particular particle is at any given time, but it is quite another to believe it can be in more than one place at a time.

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Reality: What a concept!……………………..><Ç(((Ç°>

I wish I could try this experiment at home, unfortunatley I've no way of firing one photon at a single time.

I have looked around a bit for the answer to this one ... how much of the charge of the electron actually gets through the gates?

That is if you fire off one electron do you get a full electron's worth of interference pattern.

It seems obvious that something ends up in only one place at a time because that's what we're used to, but why is it like that? Why not two places, or three places, or some random number of places? Why always just one place? With so many possibilities, that seems unlikely to always be the case.

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Life is like a box of chocolates. All of your choices are bad for you.

Yes, I agree with you that classical thinking is purely due to familiarity, it has many paradoxes that are skirted by quantum thinking-- yet we tend to think quantum thinking is the strange one! Consider motion itself-- how does an object stop being in one place and start being somewhere else? What about two objects approaching each other-- is the distance between them part of the objects, or a third entity in the problem? If the latter, how do the objects interact with that third entity such that they can collide when it goes to zero? There are so many unanswered questions in classical thinking.

In quantum thinking, these paradoxes go away-- the wave that tells the particle where to go fills the interaction volume, so when particles collide, they are merely interacting with information that was "already there". Or a better way to say that, our entire description occurs at the level of the information we are tracking. The "reality" may be distinguished from the wave functions that help us predict it, giving us an "out" for having to resolve the philosophical problems. Waves propagate and interfere, the rest follows. For example, when an object stops being somewhere and starts being somewhere else, we may say that its own wave function destructively interfered at its old position, eliminating its chance of being there, and constructively interfered at some new position, giving it an extreme likelihood of being there. The point is, probabilistic interpretations push back the unanswerable questions one level, so in that way actually make "more sense" than classical thinking does. Now we just need to figure out: how does nature convert a probability into an actual event? We've no idea as yet-- the next level of unanswerable questions. Quantum thinking seems very hard to take "too seriously"-- and that's a great triumph, not a troubling problem.

There's some good recent work on apparent FTL interactions that are dependent on smeared out waves. It's not real, no information can be transmitted FTL. Search for FTL in the recent lightweight science magazines.

Provided it still is an electron, the answer is simple. All of it.

You will get the usual signature of the electron's impact at a point somewhere on the target, and it may or may not be exactly in line with either slit. In the case of a cathode ray tube screen, it would be a speck of phosphor lighting up. A single event like this would not give any hint of an interference pattern. If we had no prior knowledge of quantum mechanics, we might attribute a deflection to a classical grazing impact on the boundary of the slit.

Well, what has to understood is that the photons are a specific quantum of energy, that means they can't really be divided up much anymore. What we understand from the experiment is that the interference pattern has to do with the nature of how photons propagate this energy. In this case, it's both a discrete particle-like position in space-time, but it also is a wave-like pattern because of the frequency of the spectrum it can occupy. Notice, I stated like for each, because even though a photon clearly acts as a particle, it also acts like a wave. Some scientists call it a wave-packets as a reference to the wave functions used to compute of this behavior. Whether or not it's truly a particle or a wave, or a wave-packet, it should be understood that this interference pattern does exist, and operates fairly regularly for each experiment related to it.

I hope that explains it for you.

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"Contrary to the ecologists, nature does not stand still and does not maintain the kind of "equilibrium" that guarantees the survival of any particular species - least of all the survival of her greatest and most fragile product: man." -- Ayn Rand

When I stop and think that a photon's speed is fixed and said photon cannot exist at rest, I feel better not knowing what it's really made of.

I disagree. It isn’t because that’s what we are used to. It is because one object by definition is a single entity. If it is in two places at once, it is no longer a single entity, but rather two entities. It is reasonable that two entities can be in two separate places at the same time.

When we are born, there are so many different possible people we could conceivably be. Why do we end up as one person? Why not two, or three, or fifty? Reason? By definition, a single entity is one.

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Reality: What a concept!……………………..><Ç(((Ç°>

And there’s the problem. Scientists run up against problems that don’t seem to have a solution. So, they craft a set of rules that make the discrepancies appear to go away. In reality, the discrepancies are still their, but the new rules skirt the paradoxes by allowing particles to do impossible things. And when someone questions those impossible things, the scientists reply that the proof is in the observations. Circular thinking. The solution is tailored to fit the problem, and the proof that it is correct is because it fits the problem. The paradoxes are skirted, good phrasing.

It moves.

The distance between them isn’t part of the objects, and it isn’t an entity. It is a spatial relationship between the two.

Those types of questions are easily and rationally answered by classical thinking.

That is just an illusion. The paradoxes are still there, they are merely skirted.

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Reality: What a concept!……………………..><Ç(((Ç°>

No, things that seem intuitively impossible. But our intuition is based on the macroscopic and classical world.



The prediction of anti-particles was not circular at all.

The scientists reply that the quantum theories are consistent with the experimental results.



The solution fits the problem and yields answers to not-yet-known problems.

The paradoxes are there because our imagination is limited to the classical world.



Sorry, but classical physics easily and rationally predicts the absence of magnetism in matter, which is utterly contradicted by any fridge magnet.

No, classical thinking does not provide the answers.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

Nice.

I'm not sure how many people realize it but what consider 'normal' or 'possible' is a consequence of evolution and our experiences. It's not Nature that is strange but us.

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"The cure for boredom is curiosity. There is no cure for curiosity."

Dorothy Parker (?)

IMO, understanding that a single object cannot be in two places at once has nothing to do with intuition. It is a matter of definition. If it is in one place, it is one object. If it is in two places, it is two objects. Why does it appear to be in two places at once? Good question, with many possible alternative explanations. The object splits in two. The object replicates itself and now there are two of them. The experiment is flawed.

Duh! Since the theories are crafted to agree with the experimental results, no wonder.

If the theories are based on similar experiments, similar situations are likely to also match the theories. No surprise there.

Apparently not. The imaginations of the scientists developing these theories seems to be virtually unlimited.

Does it prove that magnetism cannot exist?

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Reality: What a concept!……………………..><Ç(((Ç°>

Certainly it is the classical concept to say that the objects have a "spatial relationship", but what exactly is that? How does an object have a "spatial relationship", an object is just an object. The spatial relationship is in our mind, pure and simple-- no different from the quantum wave function, we're just used to being a bit more honest about that in quantum mechanics than classical. There is nothing more mysterious about quantum thinking than classical thinking, it's all 100% familiarity. Indeed, I've argued the quantum thinking is much less bizarre because it starts by recognizing we are manipulating information, there is nothing "real" in a "spatial relationship", it's a mathematical construct with no absolute meaning but great usefulness in many situations, less in others. Relativity gives a similar message, again "bizarre" and "nonclassical"-- translation: unfamiliar.
But science is never a "matter of definition", that reverses the proper logic. We choose definitions to describe reality, we do not pick concepts like "object" and then start requiring that reality satisfies our conceptual choices. We let observations tell us about reality, and if observations require concepts like "one place at a time" to be relaxed, we relax away. Anything else is clinging to outdated ideas.

Again you reverse the correct scientific logic. The experiment is never flawed, but the limitations of our concepts might well be.
It almost sounds like you are criticizing crafting theories to fit experimental results. Of course that would be a silly thing to do.

An object is an object. It resides in a particular place in the Universe at a particular time. The spatial relationship is its physical proximity to another object at that time.

No, it isn’t. While it is true that we create the words and definitions, those do not have the slightest effect on the objects in question. They don’t care what we call it. They will simply exist in a given physical relationship to each other at any given point in time.

There may be nothing real in the words we use, they are just symbols after all. But the physical relationship between two objects is quite real.

Ah, there’s your problem. Mathematics can, and often does, describe things that cannot actually or physically exist. It is important to verify the relationship between mathematical calculations and the real world often enough to retain perspective.

But that is exactly what the scientists have done. Here is an example. We see a marble, and we note how it reacts in the real world. We see a wave on the water, and see how it acts in the real world. Then we start looking at smaller and smaller “particles”, until they are so small we can no longer see them with any instrument we have. In fact, they are so small, the very act of observing or verifying them either destroys them, or permanently changes some characteristic of them. Now, some people decide that, because we see particles and waves in the macro world, that must be what exists in the subatomic arena. Now, when those “particles” do not react like they were supposed to (determined by experiments) a new set of rules is formulated to explain why they don’t. Rather than accept that they might not really be particles at all, but something that there is no analogy to in the macro world, they create all these new and irrational rules to explain how a “particle” can sometimes not act like a particle. But, maybe it doesn’t act like a particle because it isn’t. It is a lot easier to change the rules, than to discover the basic truth.

Actually, rather than clinging to outdated ideas, I advocate searching for entirely new ones.

Experiments are flawed all the time.

I am criticizing crafting illogical theories instead of finding the real reasons why things appear to behave as they seem to in certain experiments.

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Reality: What a concept!……………………..><Ç(((Ç°>

But that view ignores much of modern physics, and I can't see any reason for that other than that you would prefer it that way. It seems to miss the important recently discovered nuances of the role of the observer, in both quantum mechanics and relativity-- two more fundamental forms of physics that underpin classical physics since they reduce to classical physics in appropriate limits.
I fail to see why this is a "problem", I am in complete agreement with this statement, my point is that this is precisely all we aspire to in science, and is the very triumph of quantum thinking that I am referring to. Both quantum mechanics and relativity are wonderful examples of letting go of what is familiar to us in order to come up with a simple unifying theory that works, in the sense of predictive power of a mathematical construct, at the expense of conforming to everyday biases based on familiarity. You see that as a problem for it, I see it as the way science should always be done. Even your "spatial relationship" is really nothing but another such mathematical construct-- but you see it as something different simply because of a very high degree of familiarity. It is easy to mistake familiarity for understanding.
Actually, this is pretty close to the opposite of what happened in modern physics. It used to be thought that waves were classical entities, an alternative to "objects", but only later was it recognized (less than 80 years ago) that macroscopic waves were only examples of a much deeper phenomenon that underpinned both of our classical notions of waves and particles. So now we know that neither a macroscopic object, nor a macroscopic wave (like a water wave), is the fundamental concept of what a wave is, but both are describable completely in the language of waves. They are both extensions of the fundamental wave concept onto a scale of many many overlapping waves. The primary difference is simply the scale over which interference can occur-- if you superimpose many waves coherently, you get a macro wave that can exhibit interference on large spatial scales (e.g., a water wave), and if you superimpose many waves highly incoherently, you cannot (e.g., an object). That is simply what you are calling "wave" and "object", as though you don't recognize that both are "made of" elementary waves in much the same way that matter is made of atoms.
That type of statement would normally be viewed as holding water only in the presence of a preferable alternative concept. Your claim is that science has made a wrong turn by sticking to what has worked. But that is how science is done. And yes, it is a process, which at any point may not be the final answer-- but one does not reject what works simply because one finds it philosophically unappealing. Down that road lies creationism, etc.
No one is against the search for new ideas. But there needs to be productive suggestions about what a good approach would be, and it has to be something that has not already been tried to death (like the pseudo-classical concepts you appear to find more "logical"). It is easy to dislike a theory, especially when one does not understand it very well-- what is hard is suggesting a path toward a better one. I realize no one on this forum should be expected to do that (ATM forum notwithstanding), for that is the charter for the rare geniuses that come along, but one has to be able to say more than that the current theory stems from limited creativity. Limited creativity comes with the territory, we are humans doing human science.
Well, experiments come from reality, so are never "flawed." But I agree that the experimenters may well misinterpret what happened, or fail to control the factors they thought they controlled. But those are details that get worked out via reproducibility, etc., and present no significant challenge to science in the long run. It's certainly no reason to cling to outdated ideas when repeatable experiments suggest otherwise.
I'm not disputing that we should not leap to conclusions, and should always keep our eye out for better theories. But I'm curious what basis you are using to apply the word "illogical" in the above-- for you seem to be saying that it is "illogical" to let go of an outdated concept when new experiments expose it as such.

What you are describing has little to do with the actual solution proposed by modern physics.

Quantum theory does not say that the particle is, or appears, in two places at the same time. It says that a certain type of measurement (for example, position of a particle) on a certain type of system (a single particle going through the double-slit) in a certain state (after the particle has gone through the double-slit) will have a certain outcome with a certain probability.
In the double-slit experiment with single particles, the outcome of the position measurement and its probability is given by the superposition of two wave-packets emerging from the two two slits.

The experimental results remain consistent with quantum theory even when it is observed which way the particle is going.



But they are not circular as you claim.



Can you point us to "similar experiments" regarding the positron, the delayed-choice experiments (in the context of single-particle interference) and the Bose-Einstein condensate?



You are confusing the intuitive imagination and the development of physical theories.


Look up van Leeuwen's theorem, which proves that in classical physics diamagnetism does not exist. There is a similar theorem for paramagnetism, but the name escapes me at the moment.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

It's the same-- that theorem rules out both diamagnetism and paramagnetism in classical statistical mechanics (and ferromagnetism too). For those who do not wish to look up this theorem, it all stems from the fact that if electrons (or atoms) have no inherent magnetic moment (and they don't classically), then there isn't any way to generate one statistically by superimposing a large number of them-- and that doesn't change when you apply a time steady field. Quantum mechanics gives you ways to "hide" the magnetic moment from what is recognized classically-- via spin and atomic angular momentum.

I don't have my books here, but I am pretty sure that van Leeuwen's theorem deals only with diamagnetism.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

Well, the theorem I know is called the "Bohr-van Leeuwen theorem", so it may have been made more general than the one you mean. But it's pretty straightforward-- the magnetic moment relies linearly on velocity of the particles, and that suffices to show that no canonical distribution of particles can exhibit a magnetic moment, classically. It makes no difference at all what fields are present, or whether there are any fields present at all, as long as the system is time steady and has relaxed into its statistically most likely configuration.

That’s really good, making definitive statements about something no one understands. AFAIK, no one anywhere knows how magnetism works or why it works, any more than they understand how or why gravity works. It is one thing to make definitive statements about observations of an unknown, it is quite another to make definitive statements about the nature of the unknown.

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Reality: What a concept!……………………..><Ç(((Ç°>

I'm not sure what your objection there is, no one has claimed to "understand what magnetism is", however those who understand (a) the definition of a magnetic moment, (b) statistical physics, and (c) how to use math as a tool, know that classical systems cannot exhibit a magnetic moment. There's not a lot more I can say there, unless you'd like an outline of the mathematical proof.

Hi Everybody,

I remember studying it and it is fairly well established the phenomena that is. Quantum Stuff is hard for us to understand obviously.

Good Luck,
Loup Garou