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As I understand it, the term "collapse" is a little over-exaggerated, but why is it that we measure things as points and not waves even though particles exist as waves?
questionpost said:As I understand it, the term "collapse" is a little over-exaggerated, but why is it that we measure things as points and not waves even though particles exist as waves?
questionpost said:If particles actually existed as particles and did not oscillate like waves, shouldn't they lose all their energy by traveling real distance over time and accelerating?
bhobba said:Come again - can't follow that one. In QM you can actually derive the dynamics from Galilean invariance - you can see the details in Chapter 3 of Ballentine that I gave before. In the classical limit they behave exactly like Newtonian mechanics says they should and do not accelerate by themselves.
As far as interpretation goes - those that posted there is no consensus are correct - the view I gave is basically the shut up and calculate view - but other interpretations have a different take.
Thanks
Bill
bhobba said:I am saying they are only ever detected as particles - never as waves so the most reasonable thing to do is model them as particles. But they obey the rules of QM which is described by a quantum state that has, in some circumstances, wave-like solutions. However whether a state has a real existence is open to question - I view it purely as a device for calculating probabilities.
Thanks
Bill
questionpost said:And I assume you already know about the double-slit experiment (just to be sure)? Because I do not know how electrons could me measured in those locations they are at in that experiment without the electrons themselves following discrete wave mechanics.
Unless by "solutions" to you mean somehow working backwards from results?
Because I don't think this is just a basic pop-science mis-understanding, but at the same time, we don't actually see particles themselves as waves even though they seem to have to travel as waves to end up in the locations they do.
questionpost said:I guess it might be safer to say that a sub-atomic particle is actually neither a particle nor a wave, but its own thing.
questionpost said:So I suppose it can't be agreed upon what particles actually are, even though if particles were actually just particles they should radiate their energy away by constantly accelerating around the nucleus whereas with a wave they would simply oscillate which is not the same as accelerating? I guess it might be safer to say that a sub-atomic particle is actually neither a particle nor a wave, but its own thing.
bhobba said:It is most certainly agreed what atomic sized particles are - they are quantum objects. What can't be agreed on is how to interpret QM.
Your second statement is correct - it is not a wave nor classical particle - but a quantum particle which is something entirely different and definitely weird - although with some acquaintance you get used to it and get an idea of why it must be like that - check out:
http://arxiv.org/pdf/quant-ph/0111068v1.pdf
'The usual formulation of quantum theory is very obscure employing complex Hilbert spaces, Hermitean operators and so on. While many of us, as professional quantum theorists, have become very familiar with the theory, we should not mistake this familiarity for a sense that the formulation is physically reasonable. Quantum theory, when stripped of all its incidental structure, is simply a new type of probability theory. Its predecessor, classical probability theory, is very intuitive. It can be developed almost by pure thought alone employing only some very basic intuitions about the nature of the physical world. This prompts the question of whether quantum theory could have been developed in a similar way. Put another way, could a nineteenth century physicist have developed quantum theory without any particular reference to experimental data? In a recent paper I have shown that the basic structure of quantum theory and countably infinite dimensional Hilbert spaces follows from a set of five reasonable axioms. Four of these axioms are obviously consistent with both classical probability theory and with quantum theory. The remaining axiom states that there exists a continuous reversible transformation between any two pure states. This axiom rules out classical probability theory and gives us quantum theory. The key word in this axiom is the word “continuous”. If it is dropped then we get classical probability theory instead.'
Basically QM is necessary in a stochastic theory if you want to model continuous transformations - for the exact meaning of that see the link above.
Thanks
Bill
rodsika said:Remember a molecule composing of 430 atoms called buckyball can still interfere with itself in the double slit. These buckyballs obviously stay as particles in between (as it's hard to imagine the 430 atoms with their protons and neutrons just dissolving into waves in between). But what propel them into certain regions to form inteference patterns using your reasoning above?
questionpost said:Wow I didn't know they called it a Bucky-Ball outside of Wisconsin
rodsika said:Remember a molecule composing of 430 atoms called buckyball can still interfere with itself in the double slit. These buckyballs obviously stay as particles in between (as it's hard to imagine the 430 atoms with their protons and neutrons just dissolving into waves in between). But what propel them into certain regions to form inteference patterns using your reasoning above?
rodsika said:Remember a molecule composing of 430 atoms called buckyball can still interfere with itself in the double slit. These buckyballs obviously stay as particles in between (as it's hard to imagine the 430 atoms with their protons and neutrons just dissolving into waves in between). But what propel them into certain regions to form inteference patterns using your reasoning above?
And maybe it's not so weird after all-- maybe what was weird was the way we got away with imagining that there was an underlying cause of classical stochasticity. Maybe it was actually more weird to think of reality like an "answer man" that had an answer to any question, even questions that no apparatus was present to answer-- as if answers were somehow built into reality independently of the means to answering them. In my view, it is actually more natural, and so in a way less weird, to imagine that it is quite a fundamental aspect of reality to be utterly ambivalent to any question that the reality itself is not set up to answer. Seen in that light, indeterminism seems both inevitable and natural.bhobba said:QM does not say they dissolve into waves etc between observations - in fact it says noting at all about what properties they have independent of an observation. Weird - of course - but if you have a stochastic theory without an underlying cause of the randomness that's what's forced on you.
salvestrom said:@bhobba: I'd very much like to hear how you feel about multiverse concepts. Your descriptions here are very straightforward, "down to earth".
salvestrom said:I'd also like to see if I have a grip on your view by restating it:
From the ground up. There is field. Fluctuations occur in the field. Excitations are particles. When unviewed particles are doing something they are treated as waves - the wave function being the probability spread (is that misleading of me?) It may be possible they are actually moving like waves. When a particle/wave is interacted with (including measurement/observation) it has a definite particle form.
One more thing: what is the field? I understand the mathematical concept of scalar and vector fields - numbers assigned to points in spacetime - but what does the field record in this situation? Energy fluctuations? Or is this not the idea?
salvestrom said:Pretty sure there are only 60 atoms, but your question still stands, since that's still 720 protons and neutrons and I have no idea how many electrons.
Ken G said:And maybe it's not so weird after all-- maybe what was weird was the way we got away with imagining that there was an underlying cause of classical stochasticity. Maybe it was actually more weird to think of reality like an "answer man" that had an answer to any question, even questions that no apparatus was present to answer-- as if answers were somehow built into reality independently of the means to answering them. In my view, it is actually more natural, and so in a way less weird, to imagine that it is quite a fundamental aspect of reality to be utterly ambivalent to any question that the reality itself is not set up to answer. Seen in that light, indeterminism seems both inevitable and natural.
Ken G said:Bingo. Is the goal of physics to get reality to fit into our templates, or to keep an open mind and just let it tell us what it is? This is the dark side of Occam's Razor-- it's fine to simplify things, but we mustn't take our simplifications too seriously, or we fall into self-delusion, which is what science is supposed to cure!
You wouldn't think so, but actually, much of the debate surrounding wavefunction collapse, and its interpretations, exist expressly because of not following that rule. If we don't take our simplifications seriously (simplifications like "unitary evolution", "wavefunction reality", and "collapse"), much of the problem goes away, and we can simply treat interpretations like what they are: interpretations of simplifications.Simon Bridge said:Occams razor has us accepting, for now, the simplest models we can get away with.
The goal for physics is to let the Universe tell us what is real or not. But surely this is not controversial...
salvestrom said:It is named after an inventor called Buckminster Fuller, from Massachusets, for its resembelance to a geodesic dome he invented. The ball part comes from its similarity to the association football ball. So says wikipedia, bless them.
Ken G said:... Is the goal of physics to get reality to fit into our templates, or to keep an open mind and just let it tell us what it is?
I agree, the issue is how seriously to take the template. If our template is a circle, we then go out into the world and look for circles, because we understand circles. However, this does not mean there are actually circles out there, it means we learn something by entering into a kind of provisional pretense that there are circles out there. We must still "interpret the circles", but we needn't debate what is the "correct interpretation" of the existence of circles, because there is no existence of circles, there is only the existence of the interpretations and how we use them. The relevance here is if we substitute "circle" with "wavefunction collapse."salvestrom said:And yet, it would seem in order to learn more we do need a template, one that might give us an idea where else to look for additional information.
And still others would say that there's no such thing as something "happening on an unobservable scale", because all we can say about what happens is what we can observe to happen, and that is completely provisional to what we do in fact observe to happen. The rest is interpretations-- and templates.Others have even said we can't know the underlying reality because it's taking place on an unobservable scale, which is actually not as terrible as it first sounds. But perhaps a little disappointing.
Wave-function collapse is a phenomenon in quantum mechanics where the superposition of multiple possible states of a particle or system collapses into a single definite state when it is observed or measured. This means that the particle or system is no longer in multiple states simultaneously, but rather in one specific state.
The exact reason for wave-function collapse is still a topic of debate among scientists. Some theories suggest that it is caused by the interaction between the observer and the system being observed, while others suggest it is due to the limitations of our current understanding of quantum mechanics. However, it is widely accepted that wave-function collapse is an inherent property of quantum systems.
No, wave-function collapse cannot be predicted. The collapse of the wave-function is a random and unpredictable event, and the exact outcome of the collapse cannot be determined beforehand. This is one of the fundamental principles of quantum mechanics known as the uncertainty principle.
No, wave-function collapse does not violate the laws of physics. While it may seem counterintuitive, it is a natural consequence of the probabilistic nature of quantum mechanics. The collapse of the wave-function is a fundamental aspect of the quantum world and has been observed and verified through numerous experiments.
Currently, there is no known way to prevent or control wave-function collapse. This is because it is an inherent property of quantum systems and is not influenced by external factors. However, scientists continue to research and explore ways to better understand and potentially manipulate this phenomenon.