Seasons

That is, the region of non-zero amplitude (loudness) spread out from the fork to the rest of the room. I will call this sort of thing “propagation-3”.

Oh God - please Irina, not a third form of propagation! This is still a sinewave, propagating in classical fashion. It is just propagation, not propagation-n.
The soundwave has peaks (oh alright, crests then,) and troughs - if it's ringing A-440, then there are 880 instances of zero amplitude per second, between each peak and each trough, and then that trough and the next peak. At a lower frequency, you'd hear them, but that's way above the auditory flicker fusion threshold.

There is no "region" of non-zero amplitude floating in the room like some cloud of noise, surrounded by zero-amplitude calm. The zero and non-zero amplitudes combined are the noise.

Irina,

In particular, the two-slit experiment is very similar to the tuning fork example; in fact, if you use a tuning fork as the source of waves, and have a double slit, you will get the same sort of interference pattern. But let’s say we are using light; let’s say we have a flashlight aimed at the slits. Initially, let’s say, the flashlight is off. Psi now has amplitude zero everywhere

No. Psi is already defined, continuously across the universe for all the quanta which are currently contained in the flashlight (as well as for every other quantum that exists in the universe.) Some of these quanta, currently in the flashlight, will be excited into a high enough energy state to burst out of the bulb's filament when an electric current is applied to it, but they are still there, being probability-mapped continuously even before they do so. Psi never has an amplitude of zero, since there is always a possibility that it might suddenly turn up at the other end of the universe if we collapse the waveform by looking for it. It is just that the probability is ridiculously low (and always positive.) It is a genuinely "non-zero amplitude" phenomenon (and as such, nothing like the em-wave.)

(for sound, amplitude is loudness; for light, amplitude is brightness,

That is rather an oversimplification. Amplitude is the height of one peak + the depth of one trough. It can vary if modulated, and you can take any average you like to describe it, or specify a point and measure the point-instant value (+ive if it happens to be in a peak, -ive if in a trough.) But the loudness and brightness are not constant - they just appear to be because our brains cannot resolve that many fluctuations a second. Very low frequency noises are resolvable, which is why they discernably pulsate - you can hear the loud peaks and troughs, and also the quiet ~zero-amplitude crossover points.

for Psi, it is just “amplitude”). No scintillae appear on the screen.

It is the electromagnetic wave (and I don't mind if you describe it with Maxwell's e^i(kx-wt) or deBroglie's http:/www.be9.net/QUANTUM.JPG Fig.1,) NOT Psi that has the amplitude, is fired at the target, does the diffracting, and hits the detector causing a scintillum.
I can only repeat - Psi is merely a mathematical function that gives us a probability for every other location in the universe that, on collapsing the waveform, that particular quantum will be found there.

Every quantum in the universe can be described with its own Psi "map", which always covers the whole universe as a constant matrix of probabilities. It doesn't take a million years to "reach" a point a million light years away. In principle the (absurdly low) probability of it resolving to that point when we collapse the waveform can be calculated any time we like. That's what I mean when I say it's constant. If it propagated that probability value would have to shoot off at light-speed and take a million years to get there, just like an em-wave.

Any notion of amplitude we might ascribe to Psi is a very different one from any "proper" wave, since it has no troughs and doesn't propagate - the values are better described as eigenstates, I think.

Now we turn on the flashlight; Psi now propagates-3 from the bulb of the flashlight, to the barrier, through the slits, and

No, it is the electromagnetic wave that propagates, not Psi.

(interfering with itself in the process) onto the screen. When it arrives, we begin to see scintillae. There is a tiny delay between turning on the flashlight and the appearance of scintillae, since light travels at a finite velocity.

Yes. And Psi doesn't travel at all - it's already everywhere. And fluctuates instantaneously, for example, when the flashlight is turned on and a whole load of quanta get energised enough to form a stream of photons. Each one's Psi value for the point a million light years off changes instantly. It suddenly gets a tiny bit more likely they'll turn up there if the waveform's collapsed, since they have been energised (it is still VERY unlikely though!) Unless you're seriously going to propose faster-than-light propagation, the accepted continuous distribution model seems like a much smaller can of worms.

If we turn the flashlight off, then (after a tiny delay) scintillae cease to appear. If there were no propagation-3, why is there a delay in the appearance of the scintillae when the flashlight is turned on, and another delay in their disappearance when it is turned off?

Because it is the electromagnetic wave that propagates, not Psi.

For that matter, wouldn’t we see scintillae regardless of whether the flashlight was turned on or off? If Psi (the wave function) doesn’t go through the slits (but not the rest of the barrier), why would the presence of the slits have any effect on the distribution of scintillae on the screen?

Because it is the electromagnetic wave that goes through the slits, not Psi.

OK, let’s say we turn the flashlight on and leave it on for awhile, at the same amplitude. Then after a moment a kind of equilibrium is reached; the amplitude of Psi remains the same everywhere.

of the electromagnetic wave, not Psi.

Thus there is no more propagation-3. There is, however, still propagation-2. Because the wave-function is going from the flashlight to the screen,

The electromagnetic wave is going from the flashlight to the screen, not Psi.
    
the diffraction and interference happen on the side of the barrier opposite to the flashlight. Light diffracts when it passes through a slit.

Yes, light does. Sound does. Water does. But probability doesn't any more than happiness or bad luck.

Well, perhaps you or Penrose will come up with an entirely different explanation of the interference patterns;

No need to - it is the standard model, and needs no explaining if you distinguish the electromagnetic wave from the probability. Please Irina, give me a single reference to support the wave diffraction of Psi from anywhere. An example of how hard such a thing is to find - I've just spent an hour searching google, and I'm sorry to say that not even the flat-earthers or perpetual motion enthusiasts seem to entertain the notion:

<-1>Your search - "diffraction of Psi" - did not match any documents.
Your search - "Psi diffracts" - did not match any documents.
Your search - "Psi diffracting" - did not match any documents.
Your search - "Psi is diffracted" - did not match any documents.
Your search - "Psi was diffracted" - did not match any documents.
Your search - "Psi will diffract" - did not match any documents.
Your search - "Psi will be diffracted" - did not match any documents.
Your search - "Psi had been diffracted" - did not match any documents.
Your search - "Psi would be diffracted" - did not match any documents.
Your search - "Psi would have been diffracted" - did not match any documents.
Your search - "Psi diffraction"... bingo! 13 matches! Unfortunately in some, "Psi" stands for "porous silicon", and has nothing whatsoever to do with probability, and in all the others refers to "tilt angle"s and "lattice parameters" in crystallography (they also use most of the rest of the Greek alphabet,) and nothing at all to do with probability.
"Psi diffracted" Another 2 Matches! ... ditto unrelated to probabilities.

All the above repeated with a single "f", eg: "difract" - no further matches.

All the above, replacing "psi" with the greek letter that won't paste in here - 7 more matches for "/Psi/ diffraction" - all, on closer examination, referring to crystallography.<0>

Google's not the Word of God, I know, but I find the deafening silence out there on this topic rather telling.


You have a wonderfully creative mind, and an elegant, almost poetic model of the universe. I just don't think it's this universe

Ok, another QM question..found this..is it true?

Now, if two quantum states are "entangled" then if you change one of those states, then by definition, you must also change the state in the other system it is entangled with. For example, atomic particles like electrons have a mysterious property called "spin" (it doesn't literally mean they are spinning). It is possible to entangle the spin of one electron with the spin of a different electron. In an electron, spin has only two possible states that we call "up" and "down" (again don't take that literally). So when two electrons are entangled like this we know that when one has "spin up", the other will always have "spin down" and vice versa.

This is interesting in itself. But it becomes even more interesting when we realise that the wavefunction doesn't imply any limitation of distance or velocity. So in theory, if one of our electrons is here, and the other entangled one is on the opposite side of the universe, then if we change the spin of the one here, the spin of the one there should also change instantaneously!

[re: 4003]

Irina,

The comment of yours that I replied to was:

As for the electromagnetic wave according to Classical Physics, Quantum Mechanics says (again, speaking precisely) that there is no such thing.
As I said, Quantum Mechanics claims to supercede Classical Physics; it says that Classical Physics is wrong.

to which I responded:

Not wrong, just incomplete. It doesn't seek to replace Classical physics, just attempts to put some foundations under it (since we find the whole edifice, being built from the top down, disconcertingly doesn't seem to quite meet the ground.) Classical physics works superbly well at a macroscopic scale - it just completely fails to work at a tiny scale.

and you said:

No, wrong. Max Planck invented his eponymous constant because Classical Electromagnetic Theory gave the wrong predictions for blackbody radiation.

Yes. Classical physics gave the wrong predictions - that is perfectly true. It did not do so because classical physics itself is "wrong"; but because it's incomplete. It lacks adequate capability to model quantum-scale behaviour. Quantum mechanics does not seek to overthrow and replace classical physics - I have never heard anyone claim that at a macroscopic level classical physics should be purged, and replaced with another model.

The results it predicted were wrong, that is all. That does not mean we should throw the baby out with the bathwater, and write classical physics off completely.

Well, Psimagus, I think you have just proved the theory of multiple realities. Clearly, QM (or at least, the terminology employed) is a very different thing in your universe than it is in mine. I have once again arived at the point of considering the'debate' to be hopeless. Perhaps if I drank absinthe...

Ok, another QM question..found this..is it true?

Now, if two quantum states are "entangled" then if you change one of those states, then by definition, you must also change the state in the other system it is entangled with. For example, atomic particles like electrons have a mysterious property called "spin" (it doesn't literally mean they are spinning). It is possible to entangle the spin of one electron with the spin of a different electron. In an electron, spin has only two possible states that we call "up" and "down" (again don't take that literally). So when two electrons are entangled like this we know that when one has "spin up", the other will always have "spin down" and vice versa.


Ah yes, the Einstein-Podolsky-Rosen paradox. They rather shot themselves in the foot there - it was originally devised to disprove "spooky" quantum non-locality, but then it was actually performed.

Yes, it is perfectly true. But it would be erroneous to assume that there is any faster-than-light communication involved in this - it is spooky, but it does not break any fundamental laws. There must be causal contact to entangle them (in plain terms, they have to be put together.) Then we let them fly off in opposite directions, for a few light minutes/hours/days/years, before measuring one (I guess we'd have to have sent an observer on a slow boar to Pluto to be there ahead of time.) He measures his electron and immediately knows the value of the other. But he has no control over what the value will be, and so no prior knowledge of it. And he only gets to measure it once, and then it's gone. The information has spent all that time diverging at light speed (not faster,) and any message sent from the observer to another observer on the other side of the solar system to tip him off will only travel at light-speed (and not faster). At no point does any material or information travel faster than light.


This is interesting in itself. But it becomes even more interesting when we realise that the wavefunction doesn't imply any limitation of distance or velocity. So in theory, if one of our electrons is here, and the other entangled one is on the opposite side of the universe, then if we change the spin of the one here, the spin of the one there should also change instantaneously!

But it doesn't change. If it's measured, it's the same that's all. It was never any different, but there's no way of sending a message predicting its state to a second observer that can possibly catch up with it.

It violates only classical prejudices about how stuff "ought" to work, not any laws.

There's quite a good description @ http://en.wikipedia.org/wiki/EPR_paradox#Description_of_the_paradox

a slow boar to Pluto

Yegods! I must dilute this drink a little more - naturally I meant a "slow boat"! Though a tusked celestial messenger rooting through the heavens has a certain pagan appeal to it

Well, Psimagus, I think you have just proved the theory of multiple realities. Clearly, QM (or at least, the terminology employed) is a very different thing in your universe than it is in mine.

Just one reference to Psi propagating - that's all I ask

But I am inclined to agree - the Irinaverse is a wondrous thing, and I look forward to experiencing it at the end of days when all models are realized in the Omega Point. But until then, I fear I'm stuck in this more mathematical (but probably a good deal less magical,) strand of the multiverse.

I have once again arived at the point of considering the'debate' to be hopeless.
Perhaps if I drank absinthe...

Well, I would always recommend that!

Just one reference to Psi propagating - that's all I ask


OK, googling on "wave function propagation" (in quotes, so as to require the exact phrase to be found) produces about 576 hits. Choose any one you like.

Yes. But there are an awful lot of wave functions in existence other than Psi. And when I go to the first match (a 122 page pdf) and search for both "psi" and the greek letter /psi/, there is no match.

Oh well - try the second. Uhh, no match.

Try the third... fourth... no match.

fifth... subscriber only site, no access.

sixth... seventh... eighth... ninth... tenth... no match.

psi may apparently be the only wave-function in the Irinaverse, but in the universe that my instantiation of google describes, it is not. These links (and I'm not going to work through all 576 of them!) refer to "electromagnetic wave functions", and "semiclassical initial value representation (IVR) methods for wave function propagation", and "Coulomb wave functions", and even some more x-ray crystallography diffraction techniques by the look of it.

They are not Psi. They make no reference to Psi anywhere in their hundreds of pages. I'm actually surprised that there is not one single reference to psi tucked away in a single footnote or appendix, but this is the case. I have double checked. Not only is psi not described as propagating - it's not even mentioned.
I wonder if perhaps I have been sidelined into a universe where psi has been abolished, and noone's told me. Perhaps it never existed here. But if so, google's trapped here too.

These are not references to psi propagating. They are references to other wave-functions propagating, ie: wave-functions that can propagate (in this universe.)

Now, if two quantum states are "entangled" then if you change one of those states, then by definition, you must also change the state in the other system it is entangled with

Sorry - on closer inspection (note to self: next time at least try to read more than only every other word!) I shouldn't have agreed with this. It's not that if you change one state (because you can't,) it's if you detect one state...

You don't have any control over, or prior knowledge of what the state will be when it's detected - all you know is that one will instantly predict the other.

Some interpretations of QM say the state is hidden until it's detected. Others (seems to be the current consensus,) say there is no state until it's detected.

Sorry - on closer inspection (note to self: next time at least try to read more than only every other word!) I shouldn't have agreed with this. It's not that if you change one state (because you can't,) it's if you detect one state...

Great, Psimagus has just ruined "What the Bleep do We Know" for everyone here. You mean I can't control quantum states? What if I have a really positive attitude about it? What if I send that woman who says she channels spirits from Atlantis my money so I can learn how?

On a more serious note, I have a dumb question that I really need to ask again to try to keep up. Sorry to keep slowing you two down. I know I should read over all the old post again or google something. I am going to ask the stupid question anyway.

What exactly is "psi" again? How does it relate to a probability amplitude wave? Sorry to make you go backwards, but when I think of the slits experiments, I keep thinking photons, and then it seems to jump to psi (probably because I am not really studying everything you both told me to look at). So right now, I'm the kid in the back of the class who sat through a whole hour before raising her hand to say, "I have a question....what are you talking about?"

I know I am a PITA, but define it one more time please. I'll try to pay better attention.