Seasons

Psimgus--you know, for some reason I thought you were Scottish. Maybe it was the haggis and the pipes and the Burns references. I thought Wales had lots of mining and extra LLLs and things. How did you get to be you there?

Dear Bev:

Well, I can never resist narcisistically turning a conversation to myself, so I will mention that I have been diagnosed as having ADD (I prefer to call it "EECS", which stands for "Einstein-Edison Cognitive Style"). It has been claimed that Einstein and Edison had ADD, although this is controversial. Anyway, ... Um ... What was I saying?

hee hee watch me flip this back: My sister has ADHD and was diagnoises ADD. Pills made her sit down and write clearly, but left her feeling as if her head was stuffed with cotton.

Edison probably had some sort of ADHD; Einstein is widely believed to have been dyslexic like me.

So if we spliced a clone-style child of my DNA and yours, she'd grow up to be one crazy inventive prof, and no one would ever miss her class, even if they were never sure exactly what happened when they were there.

What, did we actually find a shred of agreement, there? What's happening to us? Where did we go wrong?

Don't speak too hastily...

A wave is often defined in Physics as a "self-propagating distubance," so if Psi is a wave in that sense, it surely propagates in that sense.

Precisely why Penrose doesn't think it should really be called a wave. It doesn't propagate, but is continuous throughout spacetime. There's even an infinitisimal chance the quantum will be found a million light years away en route through the double slit experiment, since all of spacetime is encompassed by Psi (including that point.) But not by taking a million years to propagate to that point - Psi is already there (with a value so low as to be utterly preposterous, but nonetheless not zero.)

But I have the feeling that you are using the word "propagates" in a different sense, in which case our disagreement may be only verbal.

No, I am taking the word to mean exactly what you are - classical propagation, as exhibited by classical waves and by the wave-like electromagnetic characteristics of the quantum.

Edison probably had some sort of ADHD. That's why I hate labels. There is a great danger of creating uniformity and losing genius.
As for purses etc..I like a back pack. When you are an hours driving time from anywhere, you have to be ready for CWI..that's camping without intention. In the winter you pack matches, blankets and booze..in the summer you pack bug spray, moose spray, bear spray and booze. You always have a shovel to dig out or dig in..
as for periods. Why does every conversation with or about women always has to go to pms or the like..I have never once heard men talk about testosterone poisoning.

Irina,

As for the electromagnetic wave according to Classical Physics, Quantum Mechanics says (again, speaking precisely) that there is no such thing.

But there evidently are such things, and I've not heard any quantum physicists try to argue otherwise. What most QM interpretations say (I would suggest,) is that at the quantum scale waves and particles start exhibiting characteristics of both themselves and each other. You no longer get waves and/or particles, but wavicles. But noone would deny that a stream of many quanta will exhibit primarily wave behaviour in many situations. It's just so curiously counterintuitive that a single quantum will also, in some situations (like the double slit experiment,) exhibit some aspects of wave behaviour.

As I said, Quantum Mechanics claims to supercede Classical Physics; it says that Classical Physics is wrong.

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.

So that wave doesn't exist either, according to QM.

Yes it does. It just starts behaving very strangely.

The wave that is characteristic of the quantum-mechanical view of the world is Psi. It is Psi that propagates.

It may be characteristic of many things, but it's not the only wave in any interpretation of QM I've ever come across (if, indeed, we choose to call it a "wave" at all.) It's a distribution of probabilities that covers all of spacetime. Every quantum has one (that's an awful lot of overlapping Psis!) and they all cover all of spacetime continuously.
Fortunately, being a rather theoretical mathematical device, this doesn't leave the universe clogged up with the stuff of probability to the exclusion of everything else. Hell, the universe doesn't even notice Psi so far as we can tell, any more than it stops to calculate the angular momentum of mars as it orbits the sun to make sure it stays on track. Such "laws" are made not for the instruction of the universe in what it must do, but for the convenience of sentient observers trying to understand what on earth (or anywhere else,) is going on.

Psi is not a probability wave, nor is it a Classical electromagnetic wave.

No, it's more of a map really (plotting all those lovely eigenvalues you're so fond of.) But too many people have been calling it a wave for too many years to hope to rectify the terminology in accordance with Penrose's preferences.

Ooh! When do we start splicing?

What do you want to splice? You can't splice the quantum.

Irina,

I wish I had a whiteboard, but here's a couple of quick sketches to illustrate what I mean. In Fig.1., we have a quantum (initially at X), moving (from left to right) in a 2-dimensional spacetime (it is sadly beyond the capabilities of ASCII art to clearly represent a 4-dimensional spacetime here!) According to classical physics, such a thing (be it considered particle or wave,) will move in a straight line, along the 9s.) So far so good - the spacetime is empty, with nothing to impede the progress of X.
So what (I hear you ask,) are all those numbers. Well, quantum physics builds on the classical model, but says that the classical path is only the most probable one. And that at very small scales there is an inevitable divergence - and not just inevitable, but actually unresolved until psi is collapsed by detecting the quantum.

The numbers are the probability of the quantum appearing in that cell at each instant (represented by the consecutive columns through which the quantum passes.) So Psi, in this example, is represented by this numerical "map". Probabilities can never be negative, so any wave-nature we might consider it to have must necessarily be composed entirely of peaks. And it can be mapped out across all of spacetime for every instant (thus precluding propagation - unless you claim it covers many millions of light years instantaneously. That would be to open a far, far bigger can of worms than any problems wave-particle duality could bring!)


Fig.1.


    Time
    
11111111111111111111111111111
22222222222222222222222222222
33333333333333333333333333333
44444444444444444444444444444
55555555555555555555555555555
P 66666666666666666666666666666
o 77777777777777777777777777777
s 88888888888888888888888888888
i X9999999999999999999999999999
t 88888888888888888888888888888
i 77777777777777777777777777777
o 66666666666666666666666666666
n 55555555555555555555555555555
44444444444444444444444444444
33333333333333333333333333333
22222222222222222222222222222
11111111111111111111111111111


There is always a possibility that we could find the quantum off the classical trajectory (red>9s) if we looked there for it (indeed, we often do when we do so,) but that probability reduces considerably with distance (but never to zero, even at the other side of the universe, many xillions of light years away.)
Now, since we can't look in every cell at every time, and we are complexifying the model by putting a double slit (marked by #) in the way of the beam, we only measure the initial source of each photon (X,) and the point on the detector that it hits. And we find that firing individual quanta into the experiment gives us an interference pattern in the distribution of each impact (represented by + ,) despite there never having been more than a single quantum in the space at any one time:

Fig.2.

.............#..............2 ++
.............#..............4 ++++
.............#..............2 ++
.............#..............5 +++++
.............#..............3 +++
.............#..............5 +++++
............................8 ++++++++
.............#..............6 ++++++
X............#..............8 ++++++++
.............#..............6 ++++++
............................8 ++++++++
.............#..............5 +++++
.............#..............3 +++
.............#..............5 +++++
.............#..............2 ++
.............#..............4 ++++
.............#..............2 ++



That's the paradox - each single quantum interfering with itself (because there's nothing else at any point in time to interfere with.)
Psi (or any functions thereof,) governs the probability distribution - the numbers that we map across the space, not the electromagnetic wave nature of X that causes it to exhibit this curious self-interference.
That em-wave nature might analogously be some aspect of its redness. or its symmetry, or its tetradctyly. It's a property of X, not of the probability map/wave/waveform/distribution/swamp/whatever.

And figuring out exactly how to relate functions of Psi to the model, and precisely what numbers to put where the dots are is a matter of different theoretical models and interpretations - if we move our detector to try to confirm a theoretical model by observation, we just end up moving the whole experiment, and make new fields of dots to scratch our heads over. There is an inherent immeasurability to the whole thing (as Heisenberg, and others, have pointed out.)

Hmm. That's all got rather bunched up with this darned proportional font . You'll have to try to imagine those diagrams stretched out a bit (or paste them into Notepad with a fixed width font.)

Psimagus: My "splice" remark was directed at Bev, re her remark about splicing in message 3988.

Psimagus:

I think there might be a semantic problem at work here; there are actually two distinct notions of ‘propagation’ here. I think that this is related to the fact that there are also two different notions of ‘wave’.

In everyday speech, a ‘wave’ tends to be an entity with a single crest, like a single ocean wave. A surfer can only surf on one ‘wave’ at a time. But in Physics, a wave (or wave function) can have multiple crests. For example, a sound wave produced by a voice or instrument is a whole series of crests and troughs; if an oboist (or a bagpiper) plays A-440, crests are going past your ear 440 times a second. Thus, the motion of the surface of the entire ocean can be regarded, in Physics, as the motion of a single ‘wave’ or ‘wave function.’ In order to avoid ambiguity, I suggest that we use the term, “crest” for the everyday notion of ‘wave’, and ‘wave function’ for the more general notion.