The strange many worlds of quantum mechanics

[KimB]

But if that was the case, why would that automatically make it a better theory? And yes, I do know about Occam's razor, the scientific method and so on - I make the point because there's always the possibility that the clumsiest, most-factor-laden theory ultimate is the right one, even if it sure as hell doesn't look that way right now.

This is sort of the point of Occam's Razor, though: it's a probabilistic statement. It's worth keeping in mind these other proposals, but they're highly unlikely to be accurate, due to the addition of other properties.

Granted this is a bit of a stupid point but as somebody who has to teach/explain QT interpretations on an initial/fundamental level to numerous students each year, I'm reticient to say "this is right, that's wrong" when the jury is still rather out (plus I just don't have the time anymore to really keep up with the latest developments in theoretical physics). Hell, it wasn't that long ago when it was generally expected that we should saying the MWI was billy bonkers and CI was the way to go.

Well, technically, the jury is still out on every scientific theory. The possibility that a theory is wrong is always there, and theories always need to be tested against new evidence.

And most physicists today tend to prefer the Copenhagen Interpretation, as they just don't want to think about what goes on with collapse. But they shouldn't fool themselves into thinking that the interpretation actually describes reality to any degree of accuracy, because it's simply nonsense.

 

[KimB]

Chalnoth - isn't there a famous particle-splitting experiment where one can force the spin of one of the particles then measure the other and the first forced measurement will "cause" the other to be the opposite (action at a distance)? So the quantum wave results in coherence at a distance?

No, that's not what's happening. What's happening is that when the pair of particles were emitted, they were emitted by a physical process that forces them to have opposite spin. Therefore, even if they are emitted in a superposition of states, measurement of one of the particles gives you information about the other.

 

[Mize]

No, that's not what's happening. What's happening is that when the pair of particles were emitted, they were emitted by a physical process that forces them to have opposite spin. Therefore, even if they are emitted in a superposition of states, measurement of one of the particles gives you information about the other.

I understand that, but this was an experiment where the state was forced - the measurement was designed to force up or down and the other was always the state-conserved opposite thereafter.

 

[KimB]

I understand that, but this was an experiment where the state was forced - the measurement was designed to force up or down and the other was always the state-conserved opposite thereafter.

Well, yes, that's what measurements do. They force the particle into one of the eigenstates of the measurement interaction (or, more correctly, they cause the wavefunction to decohere so that the eigenstates lose the ability to interact, and there is an observer to measure each eigenstate, each observer seeing only one).

Edit: To add more to this, the only way that you could show anything truly strange to be going on would be if you could devise an experiment where it was possible for the observer at one end to, only by looking at the entangled particles that come to them, determine whether or not the other observer was making a measurement.

 

[Frank]

I think the waveform collapse is a non-event. It simply depends on your point of view.

It's waves as they travel through time, and the measurement simply reads the current values, so to say. Even more so, you need interaction with other particles to be able to measure anything, which still uses the wave function.

We humans tend to think in linear causality, and use two different sets of measurements, one for the cause-and-effect part and another for the quantum measurements. What we see as the waveform collapse is mostly how the probability turned out as an average of the interaction of those waveforms.

Like string theory that doesn't look at individual "frames", but rather extends through time. And with all the strings (particles/waves) extending from the start to the end.

And "particles" as such have an actual (probability/interference/interaction) size as defined by their probability shell as quantum mechanics describes it, but are experienced by measurements as all having the same "size" when measured. While their actual size is defined by the amount of particles around and their energy. Seen like that, there is no such thing as "empty space".

That's my own theory, anyway.

 

[Frank]

Like a holographic spectrum analyzer. Where the waves combine and split all the time, as they interact, and try to stay within specified boundaries (quanta). And the waves aren't lines, but densities.

But that probably only helps if you've ever worked with a graphical spectrum analyzer in the first place.

 

[Frank]

Its also something that I haven't spent much time thinking about since my Grad school days, b/c I personally find the whole subject rather tedious, and am a firm believer in the 'shut up and calculate' approach.

I think it would come as no surprise if I say that I'm a firm believer of the opposite: make a coherent model in your own mind and see if you can (or want to) link that to calculations.

 

[Frank]

But if that was the case, why would that automatically make it a better theory? And yes, I do know about Occam's razor, the scientific method and so on - I make the point because there's always the possibility that the clumsiest, most-factor-laden theory ultimate is the right one, even if it sure as hell doesn't look that way right now. Granted this is a bit of a stupid point but as somebody who has to teach/explain QT interpretations on an initial/fundamental level to numerous students each year, I'm reticient to say "this is right, that's wrong" when the jury is still rather out (plus I just don't have the time anymore to really keep up with the latest developments in theoretical physics). Hell, it wasn't that long ago when it was generally expected that we should saying the MWI was billy bonkers and CI was the way to go.

I think the amount of exceptions is a good grade of any theory. The less, the better.

Edit: the more exceptions your theory has to deal with, the higher the probability there is a better theory.

 

[Frank]

And last: it might be easier to describe if we had a geometric math that used volumes and probabilities to measure entities, instead of using a single number to classify them, which we humans could grasp. And had a more direct time relation.

Wave propagation still requires point measures or formulas.

Edit: a three dimensional volume consisting of discrete objects is much easier to visualize than one consisting of unseeable things that interact through abstract formulas. Especially when you add more dimensions.