What did Einstein mean when he said, "God Does Not Play Dice" I know that is has to do something with the uncertainty principle bit i don't understand what he meant....Maybe i just don't really understand the uncertainty principle. Can someone briefly go over it.
Einstein simply meant that he didn't believe quantum mechanics (which deals with probabilities, rather than with certainties) was correct. - Warren
He was particularly against the Born interpretaion of the wavefunction, that the (real) square of the (complex) wavefunction value gives a probability of finding the particle in whatever state the wavefunction is concerned with, and that beyond that probability, and then only as the result of a measurement, physics has nothing to say. This is about as far from realism as you can get, and Einstein couldn't go that distance. Neither could Schroedinger, the author of the basic equation of QM. The EPR paper and Schroedinger's cat thought experiment were episodes in the war the two great men fought against Bohr, Heisenberg and most of the rest of the quantum physics community.
A simple example of what Einstein did not like about quantum is... If you were to set up a certain experiment (like firing photons at a piece of glass; two things could happen: the photons could either reflect or transmit through the glass) and you kept all initial conditions perfectly constant, then the same result (according to Einstein) should happen with each photon. That is, if the photon reflects off the glass the first time, then it should reflect each and every time because all conditions are the same. Quantum stated that even if the conditions are identical, you can only predict the possibility of one or the other result. So, even if all conditions are perfectly set up and held constant, some photons will reflect and some will transmit according to quantum predicitons. So God, as it were, could set up a certain situation, yet the outcome would still depend on chance, and there would be no absolute certainty about the result. Al didn't like that idea. I am unclear about whether or not Einstein actually accepted quantum. I know he had to concede several arguments to Max Born, but did he actually admit to being wrong?
Einstein's final known position was that of the EPR paper, i.e. the probabilities predicted by QM are correct, but there must be some deeper level of reality that explains them deterministically. The analogy is to thermodynamics and statistical mechanics. QM is supposed to be like thermodynamics, predicitng global properties like pressure, volume and temperature. However, you have to plug some probability laws into thermodynamics to get it going (e.g. the Maxwell-Boltzmann law). These come from a deeper theory about how atoms interact with each other, namely statistical mechanics. The probabilities arise from our ignorance about the precise location and velocity of the atoms involved and are therefore not fundamental, but are introduced for convenience. Unfortunately, Einstein was not around when the consequences of this sort of interpretation of QM were uncovered, notably by the Bell inequalities, but also via the Kochen-Specker theorem. Who knows whether he might have changed his mind in the light of these results?
its not that Einstein didn t think quantum mechanics was correct. its correctness was beyond doubt. its that he didn t think the Born interpretation was a complete description of nature.
Bohm and QM Interesting pdf file on David Bohm (Scientific America 1994) which always opposed again the superposition idea just like Einstein. The article starts with explaining some of the key points of the strange spin-behavior of electrons. http://rodin.hep.iastate.edu/jc/321-03/sciam-bohm.pdf
Thats a reasonable objection... I think the problem he had with this experimental model is that he made the false assumption that the conditions will remain the same for all the photons you fire at the glass. In his argument he is saying yes, if the conditions are the same, QM is wrong. Because all QM experiments ofthis type have a repeatibility flaw. By the very nature of the photon reflecting, you are imparting energy to the particle it reflected from, and either knocking it from its position or changing its spin, or something. So therefore, the condition of the experiment has been altered. If you fire a second photon in the same path as the first it will be impacting a different particle, or the same one but it will have different properties. And there is yet another problem with this experiment which ignores the fact that solid matter like glass is mostly empty space. Of course some photons will penetrate farther into the material (absorption) before hitting a particle that reflects it. Wouldn't it be fair to say, that if you apply the Born interpretation, that the waveform collapses on the other side of the glass? Yet that doesnt mean that no particles will get through, it simply is extremely unlikely that one will. After all, there is no value for y^2 which is negative, so you know that the waveform never passes through zero. And if there is anyplace that the waveform rebuilds, it is on the far side of any kind of interferometer device. This should tell us that since the waveform can rebuild, it never truly reaches zero, ever, or else the experiment would be over, there could be no division of probability, no situation where one proton doesnt make it but another somehow does. Experimental data shows what we should know intrinsically, which is that there is too fine a degree of control required to actually make an experiment that doesnt have some variant of this repeatibility flaw. Any QM experiment that claims otherwise is a thought experiment.
As I said , it was a simple example. The arguments between Born and Einstein are much more interesting.
In the words of the two men themselves: Einstein “I cannot but confess that I attach only a transitory importance to this interpretation. (Born's) I still believe in the possibility of a model of reality... that is to say, of a theory which presents things themselves and not merely the probability of their occurrence. Not until the atomic structure has been successfully represented in such a manner would I consider the quantum-riddle solved." Born in a eulogy to Einstein three months after his death: "A man of Einstein's greatness, who has achieved so much by thinking, has the right to go to the limit of the a priori method. Current physics has not followed him: it has continued to accumulate empirical facts, and to interpret them in a way which Einstein thoroughly disliked. For him, a potential or a field component was a real natural object which changed according to definite deterministic laws. Modern physics operates with wave functions which in their mathematical behavior, are very similar to classical potentials, but do not represent real objects. They serve for determining the probability of finding real objects, whether these are particles, or electromagnetic potentials, or other physical quantities."
This war btw, is not over at all. Its still an open question in physics, the precise nature of the measurement problem. Many physicists are interested in calculating things, and so take quantum mechanics for what its worth (eg its great to calculate) and don't think about the murky subproblems. However, if you insisted on the point and polled most physicists on what school they belong too (Copenhagen, or others) then the results are all over the place.
why go probabilistic? What is preferable about the non-local probilistic theory/interpretation over the non-local hidden variable theory/interpretation? Is it just a matter of taste? Why throw out causality for taste?
Einstein did not have anthing aganist the Heisenberg principle per se . What he did object to was the blanket implementation of the Heisenberg priciple over the whole of sub-atomic phyiscs and the implication that it was not in principle possible to learn anything definite about the sub-atomic world. His view is borne out by experiments with attosecond lasers that have recently been concluded (nature magazine ) which allow the tracing of the path of an electron in an atom.
Are you saying there is observed violation of the Heisenberg U.P.? I could not find a reference in Nature about such using attosecond lasers; although I did see references to such lasers seeing exactly what was expected by Schroedinger equations.
I usually see the dichotomy as this: a) to keep causality, reject locality; -or- b) to keep locality, assume the probabilities are fundamental (i.e. reject determinism).
Non-local hidden variable theories usually have a big problem with Lorentz invariance. Because they are non-local, the hidden variables cannot be Lorentz covariant and hence they pick out a preferred frame of reference. This goes against the spirit of relativity and we have no consistent way of deciding which frame should be the preferred one. This makes relativistic hidden variable theories, such as the Bohmian version of quantum field theory, look rather odd and unweildy compared to the usual formalism. Non-local hidden variable theories usually also pick out one type of observable as being more fundamental than the others, e.g. in Bohmian mechanics it is the position variable. This goes against the spirit of symmetry principles in physics. You may argue that these are just technical difficulties, but it is very difficult to maintain a belief in non-local hidden variable theories as fundamental physical theories. It is much easier, although still highly non-trivial, to investigate things like quantum gravity without ever introducing them. This will remain the case unless someone can find some conclusive evidence that hidden variables actually exist.
As with a lot of Einsteins quotes, some of them have 'Double-entendre's' For instance:God Does Not Play Dice?..can be a notion pertaining to the Geometry and Numbers. Dice has Six-Sides (cubed) and has six numbers-1-2-3-4-5-6. Now Einstein knows that the whole basis for numbers and counting, is based on the sums of Ten. If you are to measure something based on a counting system less than Ten, then you will have a certain variable(four) always missing? so from a geometric stance Einstein knew that :Gods Dice? Has Ten paramiters of structure, and is whole, and therefore has no Uncertainty about it. Where Bohr keeps throwing Dice that has six-sides, Einstein always throws a Dice that has Ten-Sides, this always gave Einstein an advantage in his many thought exercises with Bohr. The SIX-QUARKS for instance?..evolve directly from Bohr and Heisenburg (based on missing quantum information!..hidden variables)..the equations of Quantum Mechanics relating to the Quarks 1/3..2/3..based on the numeration of a wrong geometric Dice! Everytime a Quark is discovered..a third and two-thirds are added or subtracted? :tongue: One has to understand that German Scientists needed to be led up the garden path in the Early Twenties. Imagine then during the war the Bohr-Heisenburg "letters"..the great friends fell out and became bitter enemies..or very distant. It must have given Einsten great pleasure to see that as his activities with Bohr became ever more important as the Quantum Schools evolved. Einstein fed bohr..who communicated to Heisenburg..who eventually became Germany's main brains behind the Race for the bomb..you know the BIG-ONE, during WW2. One can almost say that the bitterness between Heisenburg and Bohr over the search for WMD, was the outcome of a 'deliberate-action-at-a-distance' coming from Einsten of course! Heisenburg played Dice..but with the wrong information
Dr Chinese I'm not to sure of this but the implications of being able to "freeze" an electron in its motion by the use of attosecond laser is already a huge infringement of the Heisenberg principle which absolutely rules against anything of the kind .
my two sense "god does knot play dice with the universe" i have always understood that to be that nothing is random...that there is an order beyond my reach...grasp...personal comprehension - not yours, nor yours. beyond the chaos...there is order, no chance, no dice. When I think to much, my brain, is a worthless piece of machinery -- it is my servant, not my master. (almost d.y.)
Einstein said that, but the quantum physicists believe he was wrong. Hawking said "God not only throws dice, sometimes he throws them where they can't be seen!"