: The only thing that sort of refutes it is this concept
: learnable in Chem I (this is just an example): Between
: two molecules, there are two equally possible ways
: that a bond will form. Therefore, the molecules are
: portrayed as having partial bonds in both ways. The
: chemistry describes that both are simultaneously
: happening. Equally, as you noted, once we observe the
: bond, it will take on its true form, and one bond or
: the other will be visible, but not both. However,
: until we observe the bond, it is in a mixed state of
: both simultaneously existing.
Well...kinda. See, the thing is that "mixed" is a relative term. A system isn't just in a mixed state...it's in a mixed state with reference to some property. Which basically means that when you apply the appropriate transformation for that property to that system's wave function, the transformed function is not an infinitely-thin spike around a certain value, but rather is "smeared" over multiple values or a continuous range.
So, really, systems are always in mixed states with reference to *some* properties. When you measure a certain property of a system, you collapse its wave function into a state which is unmixed with reference to that particular property, but now it's mixed with reference to other properties. This is another way to think of the uncertainty principle...it tells you, for a given pair of properties, how badly measuring one of them will mix the system's state with reference to the other.
Which is really freakin' weird, I fully admit. But the actual predictions are borne out by experiment...and there're certain experiments which really can't be explained away by any common-sense alternative. Here's an example.
In QM, some particles have a property called "spin." This is closely related--but not equivalent--to their angular momentum. Now, spin is a vector, with X, Y and Z components. There's an Uncertainty Principle variant for any two spin components which says that the product of their measured uncertainties is *infinite.* Which basically means that if you know *anything* about one component, your measurement of the other one will give a completely random answer.
So how do you test this? Well, you can start with a beam of particles you *know* all have the same X-spin value. (Fire a particle beam through a magnetic field in the X-direction--it'll split into multiple beams, each with a single X-spin value.) You can then measure the particles' Z-spin in *any* way you want. Simplest way is to split the beam again with a magnetic field in the Z-direction. Now measure the particles' X-spin values again in any way you want, and whaddya know? A bunch of the particles will now have changed their X-spin values so that there's roughly equal numbers of particles with any possible X-spin value. This has happened for *every* possible way we know how to measure spin.
Now it's probably possible to come up with a clever explanation of why this happens when you do magnetic beam-splitting, but when it happens using other methods as well? Similarly, there's a ready explanation for the position-momentum Uncertainty Principle when you're just thinking about measuring stuff by bouncing light off it, but for decades physicists have been trying to think of new and ingenious methods of getting around the Uncertainty Principle by measuring in other ways. Passive sensing, shining light around the particle and looking for a "shadow," interference patterns...they never work. So why not accept the Uncertainty Principle until some clever bastard *does* manage to break it? Just as we accept the light-speed limit, or conservation of energy?
: Can you deny the absurdity of that? The same is described
: that the particles which compose the empy glass on my
: desk here are strewn across the universe, along with
: everything else, and that, somehow, looking in the
: vicinity where the glass should be makes it form and
: coalesce into that location; that looking at an
: object, observing something, is the only thing which
: gives it location in the universe. Not only is this
: rediculous, it's proven wrong. That's why quantum
: mechanics is not a tool to rival Relativity, much less
: equal it, and that something better should be devised.
Well, no, it's not proven wrong. How would you go about proving such a thing as where an object "really" is in the first place? Philosophers have argued over whether objects "really" even exist for millennia.'
Now if you take the "minimalist" worldview implied by quantum mechanics--which you don't have to, it's a philosophical choice--then what QM is really saying is that things like "location" and "momentum" don't have any solid meaning. The "real world" is made up of wave functions, and the way we observe it is to poke the wave functions with measurement apparatuses and see the data they return. We don't directly "see" the properties the wave functions have, but we get hints at them from the properties of the data we get--which we label as location and momentum and so forth.
Really, is this so absurd? Is it so strange to think of a world where we can't see what's really going on? After all, you can't perceive an electron, or an atom...you can only perceive an image produced by a brain state produced by a retinal impulse produced by a photon emitted by that electron or atom. We could never hope to perceive any system (other than our own thoughts and sensory perceptions) directly, unless we're God.
And is it strange to think that you always affect a system by observing it? What sense *doesn't* work that way? Can't see something without bouncing light off it...can't hear it without bathing it in gas and making it vibrate...can't smell it without pulling molecules off it and sending them into the air. Even the most abstract types of perception--such as feeling its gravitational pull--require, by Newton's 3rd law, that the object get pushed too. QM doesn't add much new to this.
: True, it can predict certain things, without a doubt,
: with relative accuracy, but it can't predict our
: normal or celestial universe, can it? Of course not,
: so we don't use it to describe such things, only using
: it where necessary, letting pieces fall away as the
: hard evidence is uncovered which contradicts it, not
: continue to follow it blindly as if it were gospel.
Got to be careful when you say it "can't predict" stuff...there are a number of ways that term is used.
In theory, QM can most certainly be used to predict the normal universe. It doesn't get stuff wrong until you're operating on areas the size of the solar system. Which, believe me, is as wide a range of uses as any physical theory has. General relativity is just as bad at small-scale stuff as QM is at large-scale stuff. But they're both far more widely valid than classical mechanics and E&M or any other physical theory--and between them, they damn near cover the universe.
The reason why we don't use QM on human scales much isn't because it gets stuff wrong there...it's because the calculations are absolutely horrendous. Look at physics and chemistry. The entire science of chemistry is, in theory, inaccurate and unnecessary. All you need is for physics to tell you exactly what each particle in a chemical solution will do at any given time...then put 'em all together and you know what the whole chemical process is.
But in *practice,* of course, this is ridiculous. No human or computer can possibly analyze large-scale chemical reactions by looking at every single atom. So we use "sloppy" statistical rules of thumb instead...and this makes up the "science" of chemistry.
Similarly, there's no point in using QM to figure out the mechanical properties of, say, a bicycle, because you're going to be doing an insane number of calculations. Much better to cheat a bit and use classical mechanics...it's wrong, of course, but not wrong by enough to matter.
: Oddly enough, I was planning this enitire discussion to
: this point.
You sneaky devil.
: Quantum mechanics is good now, but better things can and
: do come along. Just the same, GURPS is a tool we use
: now because it works for some intensive purposes,
: despite the inaccuracies and contradictions it has
: with what we truly know. A philosphical science should
: not take president over emperical fact. Equally, a
: role playing game should not determine a barely
: related computer game. We use GURPS for what we don't
: understand yet, but it should naturally give way to
: what we find which contradicts it, not follow it as if
: it's God's plan or intention, for it is no more than
: an invention, no matter how divinely inspired.
Of course something better than QM will come along. That's how science works. You use a theory until something better turns up...at least until we get our Grand Unified Theory and it all screeches to a halt. :-) But I was serious about Bell's theorem...it really does show very very convincingly that the time of determinst theories is at an end. Wave Functions Are Your Future.
As for GURPS...I will gladly toss it aside in the face of any empirical facts...that is, things that come out of the mouths of Rob McLees and his little buddies. :-)
: Everything strewn and mixed across the universe as waves
: until observed indeed…
: The Deceiver not dead because Bungie wanted to intend
: something…right…
Careful...you'll convince every physics student on the forum that the Deceiver lives. :-)
--SiliconDream, nobly slogging through atlan.org and the Anthro library
