does quantum mechanics diproove determinism and mean that at the quantum level things don’t have causes? I don’t have too deep an understanding of the theory but it seems to me it would be impossible to proove that the randomness isn’t a result of some underlying unknown determinism.
anyone know more about this?
As you say, you can always propose some hidden underlying variables to make the whole thing deterministic. However, Bell’s theorem notes that quantum mechanics can’t be accounted for by any local hidden variable theory (i.e., one without instantaneous causation at a distance).
The arguments against hidden variable theorems in quantum mechanics are WAY over my head. But I do think it’s interesting that Albert Einstein seemed to be a staunch believer in them. “I cannot believe that God would play dice with the universe” and all that.
The quantum mechanical behavoir of particles isn’t “random”; it can be explicitly and exactly defined with a few characteristics by a relatively simple equation. The fact that the equation is a probability waveform–and thus the prediction about the future position of a particle can only be made to a certain level of probability–is irrelevent; a statistically significant number of identical particles taking the same path will fit the curve exactly.
The probabilistic nature of quantum mechanics is very real and verifiable in any number of practical experiments, the most noted of which is the double slit experiment. The wacky wierdness that comes from pre-observing the particle/waveform before it goes through both slits is a consequence that no quantum system can be observed without affecting it; by “measuring” the physical quantities (momentum, position) of a particle you interact with it and modify its waveform. This, too, is real in the sense that it really happens when you try it in a laboratory; fortunately, on the scale of everyday things, the overall interactions of many particle waveforms leads to decoherence, and real bodies act approximately like solid, discrete masses to and beyond the limits of observability. (The larger the overall system becomes, the “smaller” the waveform is; an object large enough for you to see has, for all practical purposes, a variation in position to small to be measured, even in theory.)
Quantum effects make themselves seen, very subtly, in statistical mechanics, blackbody radiation, and the fundamental mechanics of chemistry. However, these effects are so subtle that it’s been only slightly more than a century until the statistical nature of fundamental building blocks has been understood to be not just a limit to our ability to accurately observe but fundamental indeterminancy to how precisely a system of one or more particles exists in a discrete sense.
As for what all of this “means” and which interpretation of behavior on the quantum level you should select, physicist and Nobel Laureate Niels Bohr made a succinct statement almost sixty years ago that remains as true today as when he first spoke it: "There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.‘’
Stranger
I studied quantum chemistry, which is a modern attempt to apply quantum mechanics to systems at the molecular level. I was fascinated to find that the equations and systems that are an exact fit to what we observe yield messy models, while elegant conceptual models yield only approximations to observations.
The probability “nature” of elementary particles is our mind’s way of accounting for the observations we make. Einstein found this hard to accept, just as his own contemporaries had found relativity theory hard to accept. I find it easy to accept, for some odd reason. Perhaps it’s that I’ve grown up with it, or maybe I don’t understand it well enough to to be flabbergasted by it?
And, perhaps, I trust in the observables. Regardless of what we think is going on, we have to stick by what we see in experiment. That is why I liked organic chemistry most of all; it tends to look at stuff you can see. The rest I find fascinating in an intellectual way, but I wouldn’t spend my whole life doing it.
And of course, I became a software engineer. 
PS - This is what’s going on with superstring theory. The physicists and mathematicians are trying to come up with a mathematical system that encompasses all that we observe. Treat it the same way you would treat a model of the ethanol molecule built out of Tinkertoys. The model helps you visualize ethanol, compare it to similar molecules, and predict its behavior. It does not say that ethanol is made from pieces of wood!
The uncertainty principle is a fundamental result of wave/particle duality. A real world example of this is exhibited in our perception of sound. Consider a drumbeat versus a tone. The drumbeat has an exact location in time, but no real defined frequency. In QM this is the equivalent of knowing a particles exact position, but not knowing it’s momentum. The tone, on the otherhand, exists at any point between when it starts and when it finishes, but it has a well defined frequency. This is the QM equivalent of knowing the particles exact momentum, but no knowledge of the location.
The equations for the probability functions can be precisely solved for H•, He[sup]+[/sup], Li[sup]+2[/sup]… We have trouble calculating things more complex than that with certainty. I’ve made a workstation puke when I told it to calculate an aromatic Iridium. Don’t get me wrong, the approximations are getting very good, but they are just approximations. One of my molecules takes several days to run a calculation on.
The version I read in a biography of Oppenheimer was that Einstein said:
’The Old One does not place dice’
The distinction between the two versions is, to me, very significant.
Gosh…now I want a ringtone of Einstein yelling, “Cthulhu fhtagn!”
and was it Bohr that answered by saying “Einstein, stop telling God what to do”
I think you are confusing ‘old one’ with ‘deep one’
Both are valid.
It’s interesting indeed, and significant too. It reminds us that even Einstein was drastically wrong once in a while.