Dat kwade Copenhagen!
Tuesday June 20, 2006 by Patrick N. R. Julius
(The proper response? “Gesundheit… I think.”)
The Copenhagen Interpretation.
If you’ve ever heard or seen anyone talk about “quantum physics,” I’d bet any money they were talking about the Copenhagen Interpretation.
Did they say things like, “fundamental indeterminacy,” or “superposition of states,” or “complementarity,” or “observable operator” or “Heisenberg Uncertainty Principle,” or “measurement induces collapse of the wavefunction”? Then yes indeed, they were talking about the Copenhagen Interpretation.
If you haven’t ever heard anything about quantum mechanics, then I’m glad, because you haven’t been corrupted by this nonsensical dogma.
Strong words? To be sure. But you’ll see why I think they’re justified in a moment.
First and foremost, this is not quantum mechanics. This is one particular interpretation of quantum mechanics, and by any reasonable account the worst one around.
Why it persists as the accepted and taught theory is completely beyond me.
For, you see, physics is not math.
Hence I probably shouldn’t be writing this article, given that this is a math blog, and I’m talking about physics, and I just admitted that the two are not the same.
But I think it’s reasonable to write this, mostly because about 90% of current physicists don’t seem to get that physics is not math.
They think that deep insight can be found by solving equations, that something which works mathematically is therefore physically true.
How wrong they are…. You see, math is just a symbolic language, based upon principles of logic and definition. It doesn’t tell you anything about anything which isn’t math. It’s merely a tool for expressing other things.
First, you have to identify a physical thing with a mathematical structure. Once you’ve done that, you’ve already created all the assumptions which constitute the theory. Period. The rest is just consequences of that theory.
When I say that 
, that’s it. I’ve already said everything there is to say about momentum. The whole theory has already been expressed.
So when I define the meaning of the symbols and postulate Schrodinger’s equation (which just about every quantum mechanics text in the universe does without justification), I’ve already asserted everything there is to say about quantum mechanics.
Once those 
are given physical meaning, that’s it. The rest is just implications.
It’s actually the process of giving those symbols physical meaning which creates the theory. That’s the interpretation part, and that’s what most physicists don’t seem to get.
They say, “well, Schrodinger’s equation is right, therefore quantum theory [by which they mean the Copenhagen Interpretation] is right!”
Um, no… Schrodinger’s equation doesn’t mean anything until you interpret it. It’s just math, not tied to anything. It can’t be right or wrong in a physical sense.
That said, yes, Copenhagen works.
If you can call that working.
If it’s okay to say that nothing exists until you measure it (but then, how do I exist… and, uh… what’s measuring?), if it’s okay to say that somehow a deep and mystical indeterminacy underlies an obvious macroscopic determinism, if it’s okay to say that something can be “kind of” a wave and “kind of” a particle, depending on what mood it’s in, if it’s okay to say that something can be—indeed, always is—in two places at once, then Copenhagen works.
What if I told you that you don’t need all of that?
What if I told you that waves and particles both exist as separate entities, that indeterminacy is either rare or nonexistent, that particles really have well-defined positions and well-defined trajectories, that things really exist when you’re not looking at them, and nothing can be in two places at once?
If you’re an ordinary person, you’d say: “Um, yeah… so?”
If you’re a quantum physicist, I think your head starts spinning and you cry, “Blasphemer! Off with his head!”
But such a theory does exist, and it does work.
It’s called the Bohm Interpretation, and it is propounded most elegantly in the book The Undivided Universe, D. Bohm and B.J. Hiley, 1990.
All you have to do is this:
Instead of saying that position and momentum are defined by abstract “operator expectation values,” in the Copenhagen form of 
and 
, you just do something disgustingly simple: give each one a specific symbol.
. Woah, that was easy.
.
Then you let the wavefunction, previously just some weird “probability field distribution function,” become a real, physical wave, and say that: 
, and you’re done.
Then that famous Schrodinger equation gets reinterpreted to this:
.
Once you realize (as Bohm did) that the last term is just a new kind of energy, which comes from the flow of the wave, all you’ve said is that energy is conserved.
That’s all you have to do, ladies and gentlemen. All totally causal and ontological, all very simple and straightforward, just a new kind of energy and a willingness to think outside the box.
And before you assert that the usual quantum theory is experimentally verified, so is Bohm!
In fact, there are experiments in which Bohm’s predictions have been verified to 10-decimal precision for which the Copenhagen formulation can’t even be applied!
It’s a better theory. Period.
So why don’t physicists use it (generally)?
I can think of only one reason: Indoctrination.
They’re used to “mathematical elegance,” and convinced that Copenhagen has it. They’ve been trained to use Hilbert phase space and expect symplectic symmetry. That’s all very pretty, guys, but first your theory has to make sense?
They’re used to expecting “locality,” not letting anything communicate faster than the speed of light. So am I, but guess what? It actually happens. They’ve done it in the lab.
They’ve been taught that you can’t treat position and momentum differently (lest the universe explode?). Never mind that position and momentum are different things?
They don’t seem to care that the Copenhagen Interpretation is inherently self-contradictory when applied on a large scale, that it results in infinite regresses of nonsense in the simplest cosmological systems.
They don’t seem to care that the Bohm Interpretation solves just about every problem ever raised by quantum behavior in a simple and logical way, and actually fits better than relativity with our subjective experience of time.
It’s an insult to science that this situation persists.
But it’s not going anywhere, I’m sure.
No, Bohm is on the fringe, and that evil Copenhagen is here to stay.