Yeah but like 99.99999% of it is contained within a radius of a few angstroms, so the point is pretty moot. I'm afraid you're missing out on some crucial details regarding EPR. There is certain information involved that can only be successfully exchanged at lightspeed or less, hence the effects at each end appear completely random until this is done. There's no causality violation here, and this was known even to Niels Bohr himself decades before it was proven in the lab.
But atoms aren't "mostly empty space". In principle they don't have any empty space whatsoever. It's just surprisingly easy to shoot particles very close to their centers without causing significant interference, as if they were made of a light gas or a collection of tiny dots, because most of the wavefunction is concentrated in extremely tiny regions.
With that logic relativistic effects are moot as well because they affect our daily lives much less than 0.0000000001% of the time. Unless the effect falls below some quantum threshold such that it is literally irrelevant, it remains wholly relevant in the context of discussing reality. No, I understand EPR; I'm not talking about exchanging information between the particles, FTL, etc. I'm talking about "when" various observers would conclude that the system's wavefunction collapsed for each of two entangled particles. This wavefunction collapse, if it exists at all, is nonlocal. If I can calculate with certainty that particle A is in a certain state by, say, 5:00 in particle A's time, even though it had not been measured by 5:00, can we still make the claim that particle A is in an indeterminate state at that time? I would say the answer is "obviously not", but this logic leads to the contradiction pointed out earlier.
Where did you get that impression from? Brian Cox thinks that the Pauli exclusion principle in quantum physics would imply that if you heated a diamond then all the other electrons in the universe would be forced to shift energy levels. He was wrong to say this: the Pauli exclusion principle implies no such thing and quantum physics generally predicts no such effect. That's all. From the 30 seconds or so that were referenced in the OP, of Brian Cox talking about diamonds and the Pauli exclusion principle, I have absolutely no idea how he thinks of or interprets quantum physics or quantum states, and for the purposes of this thread it isn't remotely relevant. When you say this: it's clear that you're only facing a contradiction because you're assuming wavefunctions are just a representation of an observer's knowledge (which get updated when an observer learns something new). So I don't see what your point is. Yes, if you assume both that quantum states are ontologically real and that they're just a representation of an observer's current state of knowledge (and therefore not ontologically real) you have a contradiction on your hands. So what?
Actually Relativistic effects are indeed very much relevant to our lives, unless you've never looked at starlight or used GPS before. Quantum effects are also relevant in that classical mechanics wouldn't even allow the hydrogen atom to exist. When it comes to nonlocal quantum effects, then indeed it's very much negligible except in obscure areas like quantum computing, and in these cases the nonlocal effect still can't be detected without an accompanying piece of info carried no faster than lightspeed. It doesn't lead to a contradiction, because you don't know at what exact moment the wavefunction actually collapsed in any of the frames. All you know is that the wavefunction collapses at some point before any measurements are recorded, regardless of which frame you're looking at.
As for Brian Cox, he's trying to explain stuff to laymen, it can get confusing at times even for the person delivering the lecture, it's on TV with a limited time budget, so mistakes like this happen sometimes. Big deal, I doubt most of the audience will even remember 25% of what he said by sunrise.
RJ, use some common sense here: someone who believed quantum states were ontologically real would not accept that as the "very definition of the wavefunction" in the first place.
Yes, you summarize things well przyk. The wavefunction is defined to be epistemological to the extent that we adjust it as our knowledge changes (via measurements, for example). However, a knowledge set is inherently subjective, and I can therefore create a contradiction between the probability amplitude feature in the definition of a wavefunction and any ontological assignment of physical reality on that wavefunction. So what? So, the wavefunction is not ontologically real, period.
Wait, are you suggesting that it's a poor definition of a wavefunction, or that nobody actually believes in the physicality of a wavefunction? Discussing effects is ontological. Discussing a quantum state is ontological. You are both discussing nonlocal quantum state changes. This implies a physically real effect, does it not? If we're discussing state changes isn't it fair to ask "when" they occur?
The wave function is an abstract mathematical concept which represents all of a particle's properties, some of which can be measured directly, some of which can only be constrained but not measured with absolute certainty, depending on the nature of the measurement to take place and the initial conditions of the setup. Now whether it's ontologically real or there are just magic invisible fairies flying around to make it look real, the assumption that wave functions are ontological has led to the most successful matches between prediction and experiment as compared to any alternative viewpoints.
And the question of "when" is still up in the air, but we know it occurs in every reference frame before any measurements are taken, or at least what it will collapse to has already been "decided" at random by nature before anyone has had a chance to measure it. All reference frames can agree on the initial state of entanglement and that all measurements occurred after this initial state was formed; the remaining disagreements on when the entangled wavefunction actually collapsed are purely speculative and have not led to any measurable contradictions and paradoxes.
Well, utility aside, I'm pointing out that this viewpoint leads to a logical contradiction. I find it fascinating that przyk chides me for making the claim that ANYONE would take this stance, while you say that it's a marvelously practical stance to take. You and przyk appear to be unified in spirit yet contradicting each other...?Please Register or Log in to view the hidden image!
How does it lead to a logical contradiction? All that nature requires is that the total wave function preserve certain physical constants like total angular momentum, so that if you know what you get for the measurement on Particle A, you know what the probabilities were/will be for a similar measurement on Particle B after a measurement was/will be made on Particle B, and vice versa.
It's only a logical contradiction if we try to preserve causality because (as you said) the theoretical, physical wavefunction would have to collapse prior to measurement of either particle, yet do so in a manner consistent with future measurements and conservation rules. (As an aside, this is the path that lead me to conclude retrocausality.) I'm just pointing out that there is an inconsistency, in my opinion, in what seems to be the general consensus of the nature of the wavefunction.
Like scheherazade says, it gets rather difficult to sort the flyspecks from the pepper sometimes, but check this out. http://www.physicsforums.com/showpost.php?p=3682325&postcount=37 What do you think? Do you think it's really him?
Are you seriously struggling with this? Please think about this: the definition you keep citing is more or less the operational definition I'm sure you'll find in all the standard introductory textbooks on quantum physics. Textbooks which tend to focus on the side of things that aren't a matter of opinion and can't be argued with, like how to mechanically apply certain postulates of quantum physics to extract predictions which are in excellent agreement with experiments. They're not exactly big on philosophy. You know what that means? If you find someone expressing their view that quantum states are real things that physically exist, you already know one thing about them: they're not exactly the kind of person who feels duty bound to follow textbooks to the letter. And yet you expect them all to be biblical literalists when it comes to the epistemological definition of the wavefunction you keep citing?! What the hell? Basically your whole argument as I see it amounts to: Assume every proponent of the idea that quantum states are physical is an idiot. QED. which is about the silliest strawman imaginable.
No, because the manner of the wave collapse is chosen by nature at random in such a way that neither observer at either end notices any statistical anomalies in their measurements, until they correlate their results with each other by conventional means involving non-superluminal communication. If we rejected the existence of a fundamental randomness in nature, as you have previously proposed we ought to do, that's when you'd have a violation of causality both in theory and in known experiments.
I'd like to advise that one not bother trying to pontificate on the nature of many-body quantum physics, universal wavefunctions and whatnot unless they're comfortable with basic many-body quantum mechanics material such as the following: http://en.wikipedia.org/wiki/Identical_particles Multiparticle wavefunctions are built from linear combinations of the vectors contained in tensor products of single particle wavefunction vector spaces. You can isolate different components of the multiparticle wavefunction vector to represent particles that are so far apart as to have a negligible effect on the rest when they shift about over various energy levels, unless some prior entanglement was involved, and even this entanglement will be permanently broken once the initial wavefunction collapse has occurred.
Pfft…men. Please Register or Log in to view the hidden image! Will you at least look at this link and tell me what you think? This person is claiming to be Brian Cox and discussing this very topic. I checked and he is quoting from his book. http://www.physicsforums.com/showthread.php?p=3682325#post3682325
