Welcome to the Philosophy Forums! If you are not a member, please join the forums now. It's completely free! If you are a member, please log in.

Indeterminancy in physics

Use this forum to discuss the philosophy of science. Philosophy of science deals with the assumptions, foundations, and implications of science.
  • Author
  • Message
Offline

Andlan

  • Posts: 61
    ( View: All / In topic )

  • Joined: May 16th, 2012, 9:38 am

Indeterminancy in physics

Post Number:#1  PostMay 18th, 2012, 5:02 am

I am a geophysicist, not particle physicist, but am interested by the philosophical questions raised by quantum physics.

It is well known that predictions concerning individual events among atomic and sub-atomic particles have probabilities rather than exact values. We can know the momentum OR the position of a particle, but not both. This could theoretically be due to the limitations of existing quantum theories, but in common with Bohr, most physicists prefer to believe that indeterminacy is an intrinsic property of the atomic world.

Certainly, Indeterminacy has not prevented quantum mechanics being put to practical use, notably in the development of the laser and the transistor, but the potential applications did not impress Einstein, who refused to accept Bohr’s conclusion that physical phenomena need only have probabilistic, not causal, explanations. Einstein thought that the whole of physics would have to be rewritten as a result of quantum theory, and his introduction of the photon can be seen as one step along this path.

It is perplexing to me why the indeterminacy exhibited by atomic and sub-atomic particles is deemed acceptable in the particle physics domain, but not in any other (or few other) domains of science. In almost any other field, we need scientific theories to make deterministic predictions about properties: 'if I wiggle this, I get this'. Is it because quantum physics is 'waiting' for a better deterministic unifying theory to come along and replace it, for example one that will also explain gravity?

Did you know?

  • Once you join the forums and log in you will get to enjoy an ad-reduced experience. It's easy and completely free!

Offline

Steve3007

  • Posts: 743
    ( View: All / In topic )

  • Joined: June 15th, 2011, 5:53 pm
  • Favorite Philosopher: Half Man Half Biscuit

Re: Indeterminancy in physics

Post Number:#2  PostMay 18th, 2012, 2:09 pm

You'll almost certainly get some strong views expressed on this subject by the one who calls himself Xris. Scepticism of the kind you describe about QM uncertainty is his main theme.

One thing I will briefly point out is that other fields of physics don't necessarily require determinism to create accurate reliable theories. A notable example is thermodynamics. The laws of thermodynamics are regarded as among the most solid and reliable in existence, yet they are statistical. The law which states that the entropy of a closed physical system can only ever stay the same or increase is not exact. The entropy could decrease. It's just very unlikely. Whether or not the microscopic world on which these macroscopic laws are based is genuinely deterministic, the fact is that these laws are very reliable simply because they're based on the (effectively) random behaviour of such a huge quantity of particles. Randomness + huge quantities = (effectively) certainty.

Anyway, I'll leave it at that for now. Based on experience of previous threads in similar subjects in this forum, I suspect you've started a fruitful topic here that will quickly fill up with lively debate. Enjoy!
"Even men with steel hearts love to see a dog on the pitch." - Nigel Blackwell
Offline

A Poster He or I

  • Posts: 811
    ( View: All / In topic )

  • Joined: March 18th, 2011, 4:57 pm
  • Favorite Philosopher: Anaximander

Re: Indeterminancy in physics

Post Number:#3  PostMay 18th, 2012, 3:45 pm

Andlan,

Just to set up the game here up front, the view that "the indeterminacy exhibited by atomic and sub-atomic particles is to be deemed acceptable in the particle physics domain," is upheld by the so-called "Copenhagen Interpretation" of QM, named for home city of its first and most famous spokesman, Neils Bohr. It represents the standard or orthodox view of QM, and is more-or-less adhered to by the vast majority of particle physicists. It is certainly not the only way to interpret QM; the so-called "Reactionary Interpretations" of QM are plentiful and are taken seriously by many philosophers of science, general skeptics, and (gulp!) some prominent particle physicists, but they are a minority.

So here's my brief take on CI:

Philosophically, CI embraces Bohr's belief that as a science, and to remain scientific, it is not Physics' responsiblity to determine anything that is beyond the abilities of the methodological toolset of physics to investigate. In Bohr's words, "Physics is what we can say about nature."

In my opinion, the only way to appreciate Bohr's view is

(1) to understand that as a formal science, physics is ultimately mathematics, exclusively;

(2) to appreciate that the objects of study in particle physics (namely, subatomic phenomena) are not physically objectifiable except in terms of their actions upon macroscopic phenomena (namely, measuring devices, or more broadly any macroscopic "recorder" that humans can subsequently interpret);

(3) to realize, given (1) and (2), that until a recorded interaction exists, there is no other way in which these subatomic objects exist WITHIN THE DOMAIN OF THE FORMALISM OF PHYSICS except as mathematical propositions, simply because they are not otherwise verifiable.

In my opinion, the main reason why people get upset with CI is their refusal of point #3, because they seem to feel that physicists qua physicists must accept the underlying reality OUTSIDE THE FORMALISM OF THEIR DISCIPLINE of what they are studying, and so they conclude that such objects are subject to the deterministic causation of everything else humans experience.

But CI is in effect saying, No, OUTSIDE OF THE FORMALISM is precisely where particle physics cannot go if it is to remain scientific. It would be the introduction of metaphysical presuppostions into the experimental situation, and metaphysics has no place in mathematically formalized science.

(As a geophysicist, for example, the reality of the objects you study are readily verifiable by all sorts of criteria outside of your discipline, such as the evidence of your eyes and touch. Particle physicists have no such criteria outside the math which defines the objects until those objects leave their mark on the macroscopic world).

Now as to why CI is so widely accepted among physicists, I personally suspect that most physicists are philosophical Positivists by default (I say by default because most physicists are probably not very interested in philosophy). There are some physicists like Stephen Hawking who proclaim their Positivism proudly. Positivism is the perfect grounding for the acceptance of CI, given its complete eschewal of metaphysics and its belief that all of material existence must yield in principle to scientific methodologies. Conversely, Positivism when confined strictly to the validation of methodology (as opposed to being a full-blown philosophical superstructure), allows a place for religious faith in individual scientists. Therefore it becomes easy for a scientist to eschew metaphysics in the laboratory while privately "filling in the conceptual holes" with faith-based reasoning.

-- Updated Sat May 19, 2012 11:11 am to add the following --

Andlan,

A few more thoughts occurred to me this morning for answering your question:

Steve3007 mentioned how indeterminacy is accepted in classical thermodynamics. But the Copenhagen Interpretation believes there is a difference in kind regarding this indeterminacy and the kind that QM reveals.

In a statistical formalism such as is used to model the behavior of contained gasses, it is clear to all that what is indeterminate is in reality merely "under-determined," that is, it is too impractical to determine the mechanics of every single component involved in the phenomenon being studied, so statistics allow us a very good approximation for the behavior of the phenomenon as a whole, and we just don't worry about the specific mechanics of individual gas molecules. Hence, Steve3007's statement of "Randomness + huge quantities = (effectively) certainty."

Even phenomena that cannot be formalized can still be partially modelled via statistics. The fact that odds can be computed for a dice throw turning up snake eyes or winning a lottery suggests that randomness itself does not really exist as a metaphysical fact, merely an epistemological fact. So in classical mechanics, one can broadly state that probability is a consequence of a lack of complete information. CI says that this does not hold for QM. In QM, probability is a consequence of no further information to be had. Period. To my mind, the philosophical implications here depend on your view of metaphysics but what is clear is that randomness itself is the baseline where physics gets to start. There is no causation to study behind the randomness.

This makes it rather clear why we have "reactionary" interpretations of QM: the idea that randomness is the fundamental metaphysical principle of reality is unacceptable. To which a hypothetical champion of CI might say: "Fine, but let's see (1) your mathematical formalism for this causation, and (2) the empirical proof of such formalism. Until then, you don't have a scientific basis for believing in causation behind QM."

Almost 90 years later, no one has yet achieved both (1) and (2). There are many elegant formalisms fulfilling point 1 but only a very few of them suggest testable experiments, and the ones that do have not garnered support from the physics community as a whole, probably for political reasons more than anything else.
Offline

Andlan

  • Posts: 61
    ( View: All / In topic )

  • Joined: May 16th, 2012, 9:38 am

Re: Indeterminancy in physics

Post Number:#4  PostMay 22nd, 2012, 7:00 am

Steve, Many thanks for your positive comments. I certainly got an authoritative reply from A Poster. I agree with his response to you regarding indeterminacy in other branches of physics. In thermodynamics and non-linear dynamical (chaos) theory, we can say that statistics are used to generalise the complex behaviour of defined mechanisms, such as the interactions between idealised gas molecules, or the system defined by an equation. Probability here is a way to understand complexity. It is not saying that nature is inherently probablistic as in quantum mechanics (The Copenhagen Interpretation). Schrodinger tells us that we can only know where a particle is likely to be, not where it actually is, if treated as a wave.

A Poster, I was sort of playing Devil's Advocate to some degree in my post. I agree with you that QM relies on the efficacy of the mathematical formalism alone. The probablistic formulation of the wave-function has no purchase in the macroscopic world where classical properties such as position and momentum are defined. QM violates the principles of classical physics, but classical physics is just an approximation to underlying QM. It occurs to me that this can account for the paradox of Schrodinger's Cat where the cat is both alive and dead until it is observed (after which we know both its past state and its future state). This seems not fundamentally different to Zeno's paradox 'The Tortoise and the Hare,' where we can either think about motion as discrete movements or as a continuous function. Mathematics is a funny thing; not always common sensical. I do believe that these paradoxes are inevitable i.e. that there is fundamental indeterminism underlying any attempts to make the world fit our mathematical descriptions.

Nevertheless, physics is not just maths. Atoms and particles cannot be JUST theoretical constructs (refuting your point 3). It should be recalled that atomic theory was lent strong support by Perrin’s tracings of the motion of colloidal particles; an observation that confirmed Einstein’s theory of Brownian motion. Tennis balls are said to obey QM principles - it is just that the wavelengths are too small to have any measurable impact. In saying this, I don't think reality exists in ordinary space-time as Einstein implies (he asks "Do you really think that the moon does not exist when no one observes it?"). I think we have an intuitive access to reality, which prompts our investigations of the world, but reality is not a given thing, all of whose aspects can be viewed or articulated at any given moment. I think there must be causality behind the randomness, if only because we live in a causal world and it is us who are doing science. I do not have to have a scientific proof of causation behind QM.
Offline

A Poster He or I

  • Posts: 811
    ( View: All / In topic )

  • Joined: March 18th, 2011, 4:57 pm
  • Favorite Philosopher: Anaximander

Re: Indeterminancy in physics

Post Number:#5  PostMay 22nd, 2012, 12:38 pm

I do believe that these paradoxes are inevitable i.e. that there is fundamental indeterminism underlying any attempts to make the world fit our mathematical descriptions.

You have identified the primary reason I cannot support Positivism.

Nevertheless, physics is not just maths. Atoms and particles cannot be JUST theoretical constructs (refuting your point 3).

I've wondered before whether Neils Bohr's adamant insistence to the contrary was merely a way of establishing consistent methodologies and focus around the then-nascent science of QM. Personally, I don't see where it matters one way or another. If quanta are objectively real (and their dynamics are subject to causation), then CI provides an excellent practical mentality for keeping interpretation of experimental results free of metaphysical intrusions. Conversely, if the empirical demonstration of quantum mechanical behavior merely corresponds to "something our macroscopic measuring devices do under certain conditions" and QM is just a mathematical model for that behavior, the point remains that QM works, just like any good scientific model.

I don't think reality exists in ordinary space-time as Einstein implies...

To my mind, everything I've read about the evolution of QM experimentation and theorizing implicates space-time as being non-objective. Intuitively, if one allows space-time to exist as an attribute (or emergent property) of "something else," quite a number of paradoxical or non-intuitive artifacts of our conceptual systems begin to disappear.

I think there must be causality behind the randomness, if only because we live in a causal world and it is us who are doing science. I do not have to have a scientific proof of causation behind QM.

There is no harm in imagining (or believing in) causation behind QM, so long as it doesn't become a presupposition for interpreting experimental results where the experiment was not designed to determine the existence of causation. Personally, I feel the entire concept of causality is a human, ad hoc projection upon the world, but one that is so useful that I am all for the pursuit of discovering causation behind QM since it offers the potential to manipulate and predict quantum phenomena (and by implication, macroscopic phenomena) as never before.

However, let's posit that someday, unequivocal proof of causation is demonstrated behind QM. To my mind, while being incredibly valuable for the reasons stated in my preceding paragraph, I see no reason to believe that we will be any "closer" to any objective truth. Philosophically, we will be able to authoritatively claim only that, "Oh, well whaddya know...reality has a subquantum layer to it. Now I wonder whether we can model the mechanics of this subquantum layer..."

I fear that it is our very cognitive frameworks for knowledge that--if we believe them capable of truly objectifying reality--will only lead us into infinite regression.
Offline

Schaps

  • Posts: 116
    ( View: All / In topic )

  • Joined: March 30th, 2012, 2:42 am
  • Location: Russian Gulag
  • Favorite Philosopher: Nietzsche

Re: Indeterminancy in physics

Post Number:#6  PostMay 22nd, 2012, 1:31 pm

"It is perplexing to me why the indeterminacy exhibited by atomic and sub-atomic particles is deemed acceptable in the particle physics domain but not in any other (or few other) domains of science." I think that the explanation for this difference is that when one explores "physics" at the level of the sub-atomic, we are reaching the limits of intellectual understanding. The only psychologically comfortable resolution to that limitation is to accept inderterminacy as a pre-condition for further work in that area. In other "domains" of science, this limitation has not yet been reached.

I think that Einstein realized these limitations, "As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality" and "Occurrences in this domain are beyond the reach of exact prediction because of the variety of factors in operation, not because of any lack of order in nature."
Offline
User avatar

Prismatic

  • Posts: 514
    ( View: All / In topic )

  • Joined: April 22nd, 2012, 4:30 pm
  • Favorite Philosopher: John Stuart Mill

Re: Indeterminancy in physics

Post Number:#7  PostMay 22nd, 2012, 2:54 pm

Andlan wrote: It is perplexing to me why the indeterminacy exhibited by atomic and sub-atomic particles is deemed acceptable in the particle physics domain, but not in any other (or few other) domains of science. In almost any other field, we need scientific theories to make deterministic predictions about properties: 'if I wiggle this, I get this'. Is it because quantum physics is 'waiting' for a better deterministic unifying theory to come along and replace it, for example one that will also explain gravity?


No, a better and deterministic theory is not possible for mathematical reasons—the operators corresponding to the quantities do not commute. This requires a little explanation, but the ideas are not difficult.

Ordinary arithmetic operations are commutative, that is to say, for two numbers a and b, we always have
a + b = b + a and ab = ba

but some operators in quantum mechanics do not commute, specifically operators that correspond to measuring position and momentum. The result of performing one measurement and then the other is not the same as when the order is reversed. If these operators are called R and S, then it can be shown the their commutator [R,S] = RS - SR is always a positive quantity.

When quantum mechanics was developed by physicists, the underlying mathematics was not clear to them. This was rectified by John von Neumann in his 1932 book Mathematical Foundations of Quantum Mechanics in which he derives Heisenberg's uncertainty relations from the mathematics. He discusses the exact point in question:

An intuitive discussion is all the more necessary, since one could obtain at first glance, an impression that a contradiction exists here with the ordinary, intuitive point of view: it will not be clear to common sense without a further discussion, why the position and velocity (i.e. coordinate and momentum) of a material body cannot both be measured simultaneously and with arbitrary high accuracy — provided that sufficiently refined instruments of measurement were available. Therefore it is necessary to elucidate by an exact analysis of the finest processes of measurement (capable of execution perhaps only in the sense of ideal experiments) that this is not the case. Actually the well known laws of wave optics, electrodynamics and elementary atomic processes place very great difficulties in the way of accurate measurement precisely where this is required by the uncertainty relations. And in fact this can already be recognized if the processes mentioned are investigated purely classically (not quantum theoretically). This is an important point of principle. It shows that the uncertainty relations, although apparently paradoxical, do not conflict with classical experience (i.e. with the area in which the quantum phenomena do not call for essential correction of the earlier ways of thinking) — and classical experience is the only kind which is valid independently of the correctness of quantum mechanics, indeed the only kind directly accessible to our ordinary, intuitive way of thinking.
Everywhere I have sought peace and never found it except in a corner with a book. —Thomas à Kempis
Offline

Xris

  • Posts: 4336
    ( View: All / In topic )

  • Joined: December 27th, 2010, 11:37 am
  • Location: Cornwall UK

Re: Indeterminancy in physics

Post Number:#8  PostMay 22nd, 2012, 3:00 pm

Yes it is I xris.Xris who believes the conclusions are wrong because the concepts are wrong. If we start of believing subatomic particles exist then we have confusion. They may act like particles or they may act like waves but what the hell are they? We then get bogged down in finding observations are proving these particles have no mass but they still exist and even more strangely electrons happen to be in more than one place at the same time. Photons are created at the speed of light and ignore the fact that speed requires acceleration. Photons have no direction, no mass and yet they still exist. They have no mass but strangely gravity influences their path.Mathematics manages to answer the questions but mathematicians are like magicians they can conjure up answers for even god when pressed into service. We are expected to believe concepts without proof, observations without proven concepts and the result is a universe where determinism becomes a dirty word.Welcome to the world of quantum where Alice feels quite at home.
Offline

Mmfiore

  • Posts: 52
    ( View: All / In topic )

  • Joined: January 12th, 2012, 2:19 pm
  • Location: Florida
  • Favorite Philosopher: Einstein

Re: Indeterminancy in physics

Post Number:#9  PostMay 22nd, 2012, 3:04 pm

@Andlan First off I would like to thank you for bringing up this discussion. To me it is a highly relevant question in both physics and philosophy. I will be very upfront in my comments. I am not a big fan of QM or the Copenhagen Interpretation. If it were up to me I would have Niels Bohr stripped of the Noble Prize. That was a joke don’t take it seriously. So in this discussion I will take the side of Einstein and realism. Hopefully I won’t be the only one on that side. I most certainly agree with you when you say this.

I think there must be causality behind the randomness, if only because we live in a causal world and it is us who are doing science. I do not have to have a scientific proof of causation behind QM.


I believe at the very fundamental level of matter and energy the answer can be obtained by looking closely at isolated atoms and observing them. This is a way we may be able to disprove QM. I believe that studying a system suspended in isolation will reveal a deterministic chaotic system not a random one. The problem we have now in the subatomic realm is that simple deterministic laws of Newtonian mechanics can generate very complicated and yes even random motion. In the past we have tried to study systems in experiments that are very complex at the sub atomic level. These systems are so unstable that trying to observe and determine the course of trajectories in the subatomic realm is impossible using the techniques and technology currently available.

The problem we now have is that even in the simplest of systems the trajectory of objects in the system is highly dependent on the boundary that confines the system. In quantum systems the boundaries are highly irregular and dynamic. This will make it impossible for us to use classical equations to predict anything. Therefore the cause of randomness is not because of as QM says “probability is a consequence of no further information to be had.” We cannot get proper information because any attempt to measure or observe the system will only add to the complexity and unpredictability.

Here’s the catch, in Quantum Mechanics an isolated atomic system cannot take any value as it could in classical physics. Therefore I believe that this means that a simple system according to QM will be restricted to a set of possible energy levels. So when we perform an experiment and analyze the experiment using a set of Quantum Mechanics equations which employ the use of Schrodinger’s equation we can calculate with great accuracy the probabilities of a certain event occurring (the Measurement). The bottom line is this, Quantum Randomness lies not in the waves but in the process the waves describe. QM is purely statistical analysis with a fine tuning element (Schrodinger’s wave equation) as all particles and systems have a wave component. QM is just a real good tool for analyzing the sub-atomic realm. There is nothing in this process that explains how the particles move. There is nothing in this process that even explains why particles move. There is nothing in this process that explains how a particle gets from location (a) to location (b) or at what speed, certainly not both at the same time. QM cannot even explain why the speed of light is the exact value it is. Ah, but when we do experiments involving particles in the microscopic realm we did get the right answer. This is just an opening volley.

There are many good comments provided by A poster. I very much appreciate them. I would like to start with this one.

Even phenomena that cannot be formalized can still be partially modelled via statistics. The fact that odds can be computed for a dice throw turning up snake eyes or winning a lottery suggests that randomness itself does not really exist as a metaphysical fact, merely an epistemological fact. So in classical mechanics, one can broadly state that probability is a consequence of a lack of complete information. CI says that this does not hold for QM. In QM, probability is a consequence of no further information to be had. Period. To my mind, the philosophical implications here depend on your view of metaphysics but what is clear is that randomness itself is the baseline where physics gets to start. There is no causation to study behind the randomness.


How can we use probability as the basis for our reality at any level? Probability is the chance that something will happen. A chance does not provide the basis for force. A chance does not provide the basis for the existence of physical objects that we observe in the macroscopic world or the microscopic world. Chance does not make the photon travel at the speed of light. Chance does not help us at all in understanding 3 dimensional space. Imagine a thrown ball from a pitcher. The ball is composed entirely of particles that according to QM are controlled by randomness. This according to the logic of QM should mean that to some extent the ball should be somewhat unpredictable in its flight. Yet the entire collection of particles of which the ball is made of travel in a completely predictable trajectory described by classical mechanics. If the ball which is nothing more than a large pile of quantum objects can behave in a non-random means does that not imply that in order for this to happen each and every particle in the ball must be adhering to classical laws and not probabilities?

I opt for choice number 1. Probability at the subatomic level is a consequence of a lack of complete information. Probability is something that we have dreamed up. It is a mathematical abstraction with no physical existence. The only reason probability exists at all is that we need something to help us be better at guessing. It’s not good science.
Offline
User avatar

Prismatic

  • Posts: 514
    ( View: All / In topic )

  • Joined: April 22nd, 2012, 4:30 pm
  • Favorite Philosopher: John Stuart Mill

Re: Indeterminancy in physics

Post Number:#10  PostMay 22nd, 2012, 4:00 pm

Mmfiore wrote: How can we use probability as the basis for our reality at any level?


How can we not? Every measurement you make of any variable taking continuous values is indeterminate and the estimated value is only given statistically with an estimated error. The more measurements you make of an entity the greater your accuracy becomes, but it is never absolute.
Everywhere I have sought peace and never found it except in a corner with a book. —Thomas à Kempis
Offline

Xris

  • Posts: 4336
    ( View: All / In topic )

  • Joined: December 27th, 2010, 11:37 am
  • Location: Cornwall UK

Re: Indeterminancy in physics

Post Number:#11  PostMay 22nd, 2012, 4:08 pm

Prismatic wrote:
Mmfiore wrote: How can we use probability as the basis for our reality at any level?


How can we not? Every measurement you make of any variable taking continuous values is indeterminate and the estimated value is only given statistically with an estimated error. The more measurements you make of an entity the greater your accuracy becomes, but it is never absolute.

So what if every measurement is wrong? What if you have assumed a concept is correct and you make assumptions from the measurements? It only magnifies the error and you then become inventive to overcome the false concept. It occurred once before when men assumed the Earth was the centre of the universe.
Offline

A Poster He or I

  • Posts: 811
    ( View: All / In topic )

  • Joined: March 18th, 2011, 4:57 pm
  • Favorite Philosopher: Anaximander

Re: Indeterminancy in physics

Post Number:#12  PostMay 22nd, 2012, 7:43 pm

I feel that QM and the Copenhagen Interpretation are of great value regardless of whether realism is true or not, so I am going to challenge some of Mmfiore's statements for the sake of better elucidating and representing QM and CI, not to try to discredit realism. (I may eventually have to take on realism, however, depending on where the discussion goes).
I believe at the very fundamental level of matter and energy the answer can be obtained by looking closely at isolated atoms and observing them. This is a way we may be able to disprove QM. I believe that studying a system suspended in isolation will reveal a deterministic chaotic system not a random one. The problem we have now in the subatomic realm is that simple deterministic laws of Newtonian mechanics can generate very complicated and yes even random motion. In the past we have tried to study systems in experiments that are very complex at the sub atomic level. These systems are so unstable that trying to observe and determine the course of trajectories in the subatomic realm is impossible using the techniques and technology currently available. The problem we now have is that even in the simplest of systems the trajectory of objects in the system is highly dependent on the boundary that confines the system. In quantum systems the boundaries are highly irregular and dynamic. This will make it impossible for us to use classical equations to predict anything.

Here’s the catch, in Quantum Mechanics an isolated atomic system cannot take any value as it could in classical physics. Therefore I believe that this means that a simple system according to QM will be restricted to a set of possible energy levels. So when we perform an experiment and analyze the experiment using a set of Quantum Mechanics equations which employ the use of Schrodinger’s equation we can calculate with great accuracy the probabilities of a certain event occurring (the Measurement). The bottom line is this, Quantum Randomness lies not in the waves but in the process the waves describe. QM is purely statistical analysis with a fine tuning element (Schrodinger’s wave equation) as all particles and systems have a wave component. QM is just a real good tool for analyzing the sub-atomic realm. There is nothing in this process that explains how the particles move. There is nothing in this process that even explains why particles move. There is nothing in this process that explains how a particle gets from location (a) to location (b) or at what speed, certainly not both at the same time. QM cannot even explain why the speed of light is the exact value it is. Ah, but when we do experiments involving particles in the microscopic realm we did get the right answer.

I'm assuming that "the right answer" in this context means precise values (the corresponding probability equals unity, i.e., 100%) as opposed to the spread of probabilities presented by Schrodinger wave mechanics. If that is what you mean, then I mostly agree with these statements except for there being any "catch." QM is a model that works differently than a Newtonian model. To my mind, the idea that QM has "lost" the ability to compute precise values that Newton and Maxwell offered is like saying we lost the "warm analog sound" when we switched from analog to digital music production. Digital music offers so much that analog was incapable of, even though some people interpret its clarity as "brittle." Likewise, QM lets us understand subatomic behavior in ways that have given us amazing insights and technology, even though some people interpret its counterintuitive/probalistic view of matter & energy as "incomplete." So it's convenient to let audiofiles listen to 180-gram virgin vinyl when they want while others pop on their ear-buds for an MP3 file. So it's convenient to model tables, chairs, and planetary orbits via Newton while particle physicists use a different model to more readily interpret their observations.

How can we use probability as the basis for our reality at any level?


QM doesn't use probability as "the basis for our reality." It uses it to model subatomic behavior. It chooses not to investigate beyond the probabilities because it has no scientific methodology for doing so that is derivable or implied by its existing formalism.

Probability is the chance that something will happen. A chance does not provide the basis for force. A chance does not provide the basis for the existence of physical objects that we observe in the macroscopic world or the microscopic world. Chance does not make the photon travel at the speed of light. Chance does not help us at all in understanding 3 dimensional space.

You are correct, and the upshot could be that chance should be left to what it can explain. Personally, if I want to understand how subatomic behavior is going to conceptually link up with macroscopic behavior, I let QM alone and look to complexity theory. Emergence is a wonderful model for understanding how lower-order complexity and randomness generates higher-level simplicity and order.

Imagine a thrown ball from a pitcher. The ball is composed entirely of particles that according to QM are controlled by randomness. This according to the logic of QM should mean that to some extent the ball should be somewhat unpredictable in its flight. Yet the entire collection of particles of which the ball is made of travel in a completely predictable trajectory described by classical mechanics. If the ball which is nothing more than a large pile of quantum objects can behave in a non-random means does that not imply that in order for this to happen each and every particle in the ball must be adhering to classical laws and not probabilities?

No, that is not implied, because you are ignoring the phenomenon known as decoherence. You cannot arbitrarily ignore that the presence of the quadrillions of overlapping wave functions inherent in the modelling of a baseball's quanta are interacting, amalgamating into what is sometimes referred to as a Schrodinger Pulse, most of which is constituted by the cancellation of most of the waves' extremes of amplitude, resulting in an overall wave function for the baseball that is so tightly bounded, that the probability of that baseball displaying any macroscopically visible quantum effects is virtually nil. (There are other ways for QM to model this, such as Feynman's sum-over-histories approach). The very existence of macroscopic phenomena implies decoherence, given that they are indeed made up of quanta capable only of quantum mechanical behavior.

More interesting to me is that even if one could truly calculate the wave functions of every quantum in a baseball, you could in principle reach a set of results that describe the Schrödinger pulse, but nowhere would the baseball per se be evident as a discreet entity. Indeed, such a quantum-level analysis would have a difficult time isolating where the quanta of the baseball end and the surrounding air begins. This is why we have multiple models of reality. The macroscopic world displays emergent properties better modeled by complexity theory than QM.

Probability is something that we have dreamed up. It is a mathematical abstraction with no physical existence. The only reason probability exists at all is that we need something to help us be better at guessing. It’s not good science.

Given its record for accurate prediction, probability is actually excellent science so long as we continue to believe that it is indeed a mathematical abstraction with no physical existence. The Copenhagen Interpretation says in effect, "Randomness is the baseline for physics." It does NOT say that "Randomness is the fundamental metaphysical principle of reality." There is HUGE difference between these 2 statements, conceptually, philosophically, scientifically, and practically.

Once we can theorize properly (hypotheses with testable conclusions) about what is behind the probability--instead of stretching inappropriate models into areas where they don't belong (i.e., cannot yield testable conclusions)--then I will agree that to uphold probability as the baseline for physics is no longer good science. Until then, I think Bohr is being responsible to science when he says, "Physics is what we can say about nature."
Offline
User avatar

Prismatic

  • Posts: 514
    ( View: All / In topic )

  • Joined: April 22nd, 2012, 4:30 pm
  • Favorite Philosopher: John Stuart Mill

Re: Indeterminancy in physics

Post Number:#13  PostMay 22nd, 2012, 10:47 pm

Xris wrote: So what if every measurement is wrong? What if you have assumed a concept is correct and you make assumptions from the measurements? It only magnifies the error and you then become inventive to overcome the false concept. It occurred once before when men assumed the Earth was the centre of the universe.


I didn't say that every measurement is wrong, merely that it is indeterminate, fixed only within an error due to artifacts of the measuring apparatus and actual measurement errors. When you say that a series of measurements shows a given length is 100 feet to within an error of ±3 feet, you are not saying that the measurement is wrong, a thing you cannot know, but rather something like "there is a 95% probability the length is between 97 feet and 103 feet." The point is that probability enters into all our measurements of continuous variables.
Everywhere I have sought peace and never found it except in a corner with a book. —Thomas à Kempis
Offline

Xris

  • Posts: 4336
    ( View: All / In topic )

  • Joined: December 27th, 2010, 11:37 am
  • Location: Cornwall UK

Re: Indeterminancy in physics

Post Number:#14  PostMay 23rd, 2012, 5:04 am

Prismatic wrote:
Xris wrote: So what if every measurement is wrong? What if you have assumed a concept is correct and you make assumptions from the measurements? It only magnifies the error and you then become inventive to overcome the false concept. It occurred once before when men assumed the Earth was the centre of the universe.


I didn't say that every measurement is wrong, merely that it is indeterminate, fixed only within an error due to artifacts of the measuring apparatus and actual measurement errors. When you say that a series of measurements shows a given length is 100 feet to within an error of ±3 feet, you are not saying that the measurement is wrong, a thing you cannot know, but rather something like "there is a 95% probability the length is between 97 feet and 103 feet." The point is that probability enters into all our measurements of continuous variables.

If you do not know what you are measuring then the results will appear indeterminate. The apparent randomness that indicates an indeterminate quantum universe could be our ignorance, not an indeterminate nature. Hidden variables are completely ignored and concepts are accepted with religous fervour. Constant invention becomes the norm and mathematics simply support false concepts. I understand the idea that the more we measure the more accurate the mean value becomes but when there is no random effect only our false concept, we are simply using it for practical purposes not the truth. As I said before when the Earth was considered the centre of the universe, mathematics supported that concept with more and more complex formula and the mathematicians were admired. I admire science its knowledge but it does have to accept it might be fundamentally wrong on this issue.
Offline

Mcdoodle

  • Posts: 229
    ( View: All / In topic )

  • Joined: April 12th, 2012, 3:48 am

Re: Indeterminancy in physics

Post Number:#15  PostMay 23rd, 2012, 6:41 am

A Poster He or I wrote:

Probability is something that we have dreamed up. It is a mathematical abstraction with no physical existence. The only reason probability exists at all is that we need something to help us be better at guessing. It’s not good science.

Given its record for accurate prediction, probability is actually excellent science so long as we continue to believe that it is indeed a mathematical abstraction with no physical existence. The Copenhagen Interpretation says in effect, "Randomness is the baseline for physics." It does NOT say that "Randomness is the fundamental metaphysical principle of reality." There is HUGE difference between these 2 statements, conceptually, philosophically, scientifically, and practically.

Once we can theorize properly (hypotheses with testable conclusions) about what is behind the probability--instead of stretching inappropriate models into areas where they don't belong (i.e., cannot yield testable conclusions)--then I will agree that to uphold probability as the baseline for physics is no longer good science. Until then, I think Bohr is being responsible to science when he says, "Physics is what we can say about nature."


I'm with Poster and Prismatic in this debate. I'd only say that the clause 'Once we can theorize properly about what is behind the probability...' is to me an unnecessary step too far. The thing-in-itself, 'underlying reality' - why, if there are no gods, do we need to believe in such a possibility? Can't we settle for the multiplicity of our models, and the acceptance that there'll never be a theory of everything?
Next

393487_FreedomWorks Special Edition DVD

Return to Philosophy of Science

Who is online

Users browsing this forum: No registered users and 2 guests

Philosophy Book of the Month Updates

The January book of the month is Two Cheers for Anarchism by James C. Scott. Discuss it here or buy it here.

The November book of the month is On the Internet by Hubert L. Dreyfus. Pick it up, read it and discuss it with us as a group!