Modern physics, Heisenberg, and questions of free will

[Brillig]

So much physics... and yet, I can't help feeling that a point is being missed here.

Even taking into account the notions of observer effect, the uncertainty principle, the wave-particle duality of matter, it still seems to boil down to this: the behavior of elementary particles can be expressed as a function. Even if it's a probability function, there is still a function that describes its behavior. This in turn implies that the behavior of a larger system of particles can be, at least in theory, also be described with a similar, but more complex, probability function.

If this is true, then any decision that one might make can also be described, in theory, as a function. While it may not be possible to say with certainty that I would prefer a red car over a blue one, it should be possible to determine that there is a X% probability that I would choose a red car over a blue one. (Assuming all factors can be calculated). If all of our actions can then be exactly quantified in terms of the probability that we would choose a certain outcome, and the choices are random (with the calculated distribution), then can we be said to have free will?

Certainly, from an external observer's viewpoint, since the choice cannot be definitively determined, it would appear that a choice exists, but this is an illusion - if you cast a die, does it choose to come up with a four? Is the die exercising free will? Surely not. So if your choice can be described accurately as a probability function, then free will does not exist.

Or does it?

Sidebar: Understanding Quantum Mechanics

Why is understanding quantum mechanics so difficult? I think that part of this has to do with how the human brain is wired - specifically, that the human brain is evolved in a direction that makes it intrinsically difficult to accept the core findings of quantum theory.

Our brains are, essentially, decision making engines. Evolutionary pressure has driven us in the direction of having brains that a) make decisions correctly and b) make decisions swiftly. While it's obvious what the value of a correct decision is, it's important to realize that a swift decision is also often critical. It's no good deciding that the lion is dangerous after you're inside his belly. In order to make decisions swiftly, the human brain has acquired an incredible ability to simplify (very little of which is on display here, sorry). Our ability to make inferences, generalize, extrapolate, all come together to make good decisions faster.

And what's another way to make decisions faster? To avoid complexity. We're generally programmed to try to simplify everything down to binary conditions. (Why do you think there are so many jokes about "there are two kinds of people..."? This is not an accident.) Binary decisions are easy to make. The lion is dangerous or not dangerous. Jumping off a cliff is good or bad. Over time, we learn to make more complex decisions, but they are almost invariably built up of multiple binary decisions. E.g., jumping off a cliff is bad, except when it's to escape a lion, who is dangerous.

What I'm getting at is this: thinking in terms of probabilities is not a natural behavior for the human brain. If I tell you that there is a 30% chance that you will meet a hungry lion trekking across the savannah, the first thing that goes through your mind is (I'm betting), what an encounter with a lion would be like. Or less probably, what trekking across the savannah would be like. In either case, the first thing that crosses your mind is a scenario that completely ignores the probability included in the statement. Instead, the binary, either/or part of your brain has picked a scenario, and is off merrily running with that.

So don't feel bad that quantum mechanics feels counter-intuitive. It is. Your brain is wired that way.

Forget the physics for a moment and let's step back and consider the question: "Do I have free will?"

Well, it may be a little glib, but that depends on what you mean by "I" and "free will".

Free will may actually be the easier of the two to deal with - although philosophers have been debating it for millenia. There are actually a wide variety of possible definitions of free will, many of which actually do not conflict with a probabilistic-deterministic view of human action. Fortunately for us, we're not interested in those

Instead, what we're interested in are the "free-est" of free will philosophies. What are called incompatibilist views.

Sidebar: Compatibilism

It might surprise you to know that many philosophers believe that there is no contradiction between causal determination and free will. This is the school of compatibilism, wherein the general idea is "to say that I am able to do otherwise, is to say that I would do otherwise if it were the case that ..." , where the ellipsis is filled by some elaboration, such as “I had an appropriately strong desire to do so, or I had different beliefs about the best available means to satisfy my goal, or ...” In short: something about my prevailing character or psychological states would have differed, and so would have brought about a different outcome.

There are some divisions within the incompatibilist schools, mainly to do with how limited or broad the scope of possible choices is - while some feel that there are some constraints upon the choices we make as a function of our selves, others believe that all choices are possible. Fortunately for us, those fine gradations don't bear much on the question of the day.

What is interesting is every school of incompatibilist thought holds that free will is found in the lack of external causal factors. That is, there is something other than external causal factors that inform our choices.

The wrinkle we're talking about today is that we've added the very chemistry of the brain into the list of "external causal factors". So, if we look very carefully at the question we've asked, free will, if it exists, must exist outside the physically describable brain and body (assuming arguendo that the brain and body are, in their entirety, physically describable as posited in the beginning).

Which brings us around to the other question: What is "I"?

This is, of course, yet another philosphical conundrum. Obviously, if you accept that the "I", your identity, exists not solely as a property of your physical existence (e.g., you have a 'soul'), then the question of free will is (at least potentially) easily resolved (i.e., it is from the 'soul' that the choice is non-deterministically made). On the other hand, if you believe that your identity is a function of your physical existence, then things get interesting.

I'm going to assume that if you reject the idea that your identity is severable from your physical existence, then you likewise would reject the idea that your free-will can nonetheless come from something severable from your physical existence. (Otherwise, the question becomes trivial).

If this is so, then I'm afraid I have to break it to you that you don't have free will.

Unless one of the following appeals to you.

A) The many-worlds hypothesis beloved of science fiction. This holds that every choice that can be made is actually made, and that each choice spawns a universe of its own. Even if the universes do all exist, the "I" that represents you could have made the choice that brought it to this universe, and that is the exercise of free will.
(This might also imply that another "I" made an equally free choice to choose the other alternative(s).)

B) The incalculable nature of the problem. This was touched on above, but there are some problems that cannot be solved. You cannot write down the largest number, for example. It's hard to put into words, but it's entirely possible, even probable, that describing the actions of the human brain as a function is a problem of the same order (I like to call these "problems that are bigger than the universe" - meaning that, even if you somehow had all the universe at your fingertips, you still couldn't solve them.) It may seem semantic, but I think it's defensible to say that something that cannot be described cannot be held to be deterministic.

C) This space intentionally left blank.

[dixieflatline]

Originally Posted by judicial clerk

Dixieflatline, Isn't there a theory that when the single electron is projected through the slits, it is ineteracting with the another "universe" that is just right "there"?

Hi JG.

Yes but that theory is untestable so I don't think it garners too much support amoung the science community. It certainly could be true though. In fact there also is a "many worlds" theory that goes something like: every time a wavefuction with multiple possiblities is collapsed for each possibility a world is created. As times goes forward these worlds spin off like a tree with lot's of branches. Also untestable but a competing theory to the Copenhagen way of thinking if you prefer that.

[QuikSand]

Brillig, glad you joined the thread.

I can't tell whether the sidebar above on "Understanding Quantum Mechanics" above is your own work (I presume it is), but it is nonetheless very clear to me. Doesn't really help me in understanding the concept itself, but it "clicks" with me tohelp understand why I don't understand, which has at leat some appeal.


The concept you raise first, though, about the probabilistic nature of matter is one that simply doesn't ring true to me at any level. I think I understand the conjecture, and I understand how it leads logically to a variety of conclusions... but it just doesn't have any "sense" of its own that I can really approach.

I realizee that I am just essentially restating that "I don't get it," but that's really where I am with all this. I have heard and am familiar with a variety of descriptions on the subject generally, I follow the concept and results of the better know tests, and am at least able to process the evidence... but at the end of the line, it doesn't realy "come together" for me in a way that I'd feel comfortable with.


I think my next book needs to be in a different direction. Perhaps the Wu-Tang Manual.

[cartman]

Originally Posted by QuikSand

I think my next book needs to be in a different direction. Perhaps the Wu-Tang Manual.

I think that Beavis and Butthead's Ensucklopedia would also be a good change of pace.

[moriarty]

Originally Posted by QuikSand

I think my next book needs to be in a different direction. Perhaps the Wu-Tang Manual.

How bout Bill Bryson's A Short History of Nearly Everything ?

Much lighter material with some history and light science?

[dawgfan]

Originally Posted by moriarty

How bout Bill Bryson's A Short History of Nearly Everything ?

Much lighter material with some history and light science?

A very good book, but I'm not sure it can really address the issue of this thread.

[moriarty]

Originally Posted by dawgfan

A very good book, but I'm not sure it can really address the issue of this thread.

Well when he said he wanted to go a different direction and suggested the Wu Tang Manual ... I sort of took him at his word. I haven't read Wu Tang's Manual but I doubt it covers quantum physics (alternate realities maybe).

[dawgfan]

Originally Posted by Brillig

B) The incalculable nature of the problem. This was touched on above, but there are some problems that cannot be solved. You cannot write down the largest number, for example. It's hard to put into words, but it's entirely possible, even probable, that describing the actions of the human brain as a function is a problem of the same order (I like to call these "problems that are bigger than the universe" - meaning that, even if you somehow had all the universe at your fingertips, you still couldn't solve them.) It may seem semantic, but I think it's defensible to say that something that cannot be described cannot be held to be deterministic.

Good stuff Brillig. The description of the inherent difficulties of understanding the complexities of quantum mechanics based on the nature of the way the brain is wired is something I've pondered for quite some time, and not just in the application to understanding quantum mechanics. The more you understand how the brain works and why it works the way it does, the more you understand the difficulties so many people have in grasping complex and subtle problems and why people are so enamored with looking at everything as "black and white", "us vs. them", "right and wrong". I've come to calling this "digital thinking".

It takes more effort to look at things in a more complex way and attempt to understand all the factors that go into defining any situation (what I refer to as "analog thinking"). The problem here is that it is essentially impossible to know all factors that go into comprising most situations; however, in many cases simply knowing the most prominant factors is usually enough.

However, it can be those subtle factors that fly under the radar that can make the difference. As stated before, a great example of the complexity of understanding how things work is the science of weather forecasting - for all the shit they take, (good) weathermen are usually quite accurate, but there are still factors that elude their modeling and cause inaccuracies in their predictions.

Still, it's my contention that as the world gets more overtly complex and we as people face more and more decisions and have to digest more and more information that it's an instinctive response to simplify things around us in order to not feel overloaded. I believe if you look into the study of consciousness, one of the first concepts you'll come across is the idea that our brain filters out a great deal of the information our senses provide us in order not to be overwhelmed.

As you state in your scenario B) above, I believe in a "clockwork" universe, but I think the calculations that would go into predicting my behavior are so complex as to have the appearence of "free will". Well, much of my behavior - it's still a near-certainty that I'll have a very positive reaction to seeing pictures of Jennifer Connelly...

[dawgfan]

Originally Posted by moriarty

Well when he said he wanted to go a different direction and suggested the Wu Tang Manual ... I sort of took him at his word. I haven't read Wu Tang's Manual but I doubt it covers quantum physics (alternate realities maybe).

Good point. I'd highly recommend Bryson's book to all.

[QuikSand]

Originally Posted by moriarty

How bout Bill Bryson's A Short History of Nearly Everything ?

Much lighter material with some history and light science?

I have a copy around the house somewhere -- I once got about a third of the way through it, put it down, and never got back to it for some reason. I like Bryson fine, just didn't click with me, for whatever reason. But it might indeed be worth picking up again... while I have a little momentum. (There I go again with the classical physics... ignoring everything we now understand about relativity and quantum mechanics -- I'm so old school!)

[QuikSand]

Since someone else already braved this one...

Originally Posted by Brillig

B) The incalculable nature of the problem. This was touched on above, but there are some problems that cannot be solved. You cannot write down the largest number, for example. It's hard to put into words, but it's entirely possible, even probable, that describing the actions of the human brain as a function is a problem of the same order (I like to call these "problems that are bigger than the universe" - meaning that, even if you somehow had all the universe at your fingertips, you still couldn't solve them.) It may seem semantic, but I think it's defensible to say that something that cannot be described cannot be held to be deterministic.

See, for me, this is something that my intuition just rejects completely.

Let's say that the universe is indeed made up of matter and energy, that exists along some sort of spscae-time fabric. Got it, fine.

And let's say that the motion of every thing in the universe is, in fact, a function of the series of physcial forces that arise from the existence of the various other things in the universe -- their location relative to one another, their interaction with one another, and so on.

Surely, this would be so inconceivable to actually calculate, that we could never actually hope to make that calculation of what excatly should happen. It is, by any reasonable standard, beyond our abilities. I have no problem conceding that point.

I do not, however (and this is from intuition and nothing more) then accept the notion that the inability to calculate or measure these collective effects somehow invalidates their existence. A particle floats in space, and its movement is determined exclusively by the various forces around it, though they are so many in number as to be incalculable. So what? The particle doesn't need to calculate things, it just reacts to the forces themselves. The particle isn't following a map, it's simply in a reactive state. As are (by extension) all other things in the clockwork universe. Just because things cannot be measured and predicted, doesn't mean the model isn't an accuate description of what is actually happening.


I have heard some summaries of the Copenhagen school, and it just smacks of "backdoorism" to me. But once again, I have been pleading ignorance and lack of understanding on all these matters, so this is quite consistent with that stance.

[QuikSand]

Originally Posted by dawgfan

As you state in your scenario B) above, I believe in a "clockwork" universe, but I think the calculations that would go into predicting my behavior are so complex as to have the appearence of "free will".

Okay, I find this conclusion superficially tempting as well, but to me, it doesn't make any real sense.

If, in fact, the universe is simply a physical reaction of things in the cosmos, reacting to fixed, determined forces upon one another, then everything that happens should essentially result as a simple function of those physical activites.

If I use my finger to hit a key on my meyboard, it's physically becaose of some nerve impulse sent to my body from my brain. And my brain did so because of some chemical activity that stirred in me the notion to type that key. If you buy the action-reaction theory of all activity, then this has no beginnign and end, it's just a series of motions, all stacked up end to end.

If that's true, then -- why would there be any order in anything? Any system we understand, when motion is introduced, tends toward disorder. The more complex, the more disorder it finds. Why on earth (or elsewhere) would the product of some physical reactions gone amok have such semblance of rationality to them? We experience cause and effect, we think of things as a result of what has happened -- it's just really hard to imagine that those chemical reactions in your body upon seeing Jennifer Connelly are simply some random physical effect, determined more by some oddball reactions of electrons and masses flying about in and around your person than they are a function of your dirty little mind and where it leads, on its own, after such an exposure.

[-Mojo Jojo-]

Originally Posted by QuikSand

If that's true, then -- why would there be any order in anything? Any system we understand, when motion is introduced, tends toward disorder. The more complex, the more disorder it finds. Why on earth (or elsewhere) would the product of some physical reactions gone amok have such semblance of rationality to them?

Living organisms don't violate the 2nd Law of Thermodynamics, although viewed in a particular perspective they might seem to. Living organisms consume a great deal of energy to maintain their organization (the semblance of rationality). That's why we have to eat/photosynthesize all the time. And while the beings themselves remain organized, that constant burning of energy nets an overall increase in entropy.

[Ksyrup]

I've been trying to jump into this thread since it started, but couldn't find the right place or the right idea to express my thoughts on the subject. Then I realized that's because I have no thoughts on the subject. But I still felt the need to post something, just to say I did. So here goes...

[rkmsuf]

Originally Posted by Ksyrup

I've been trying to jump into this thread since it started, but couldn't find the right place or the right idea to express my thoughts on the subject. Then I realized that's because I have no thoughts on the subject. But I still felt the need to post something, just to say I did. So here goes...

Somehow you were destined to post here. Free will had nothing to do with it.

[QuikSand]

Ksyrup probably had the right idea.


I'm bumping this thread because I have done a little more reading on the topic, and again up against the measurement/existence precipice, and I once again am unable to make any more progress with my own intuition.

I understand the statements that learned people make about these topics -- it's not that I don't understand what people are saying ro claiming. I just am completely unable to process it as having real meaning.

Alas... thanks to those who, in this thread, have given me even more to think about. I am reaching the conclusion that I simply will never make intuitive peace with these concepts, and will have to come to terms with that. I appreciate the interesting contributions, though.

[Vince]

This has been a fascinating read. I wish I could add to the discussion.

[Ksyrup]

Pancakes, anyone?

[Bonegavel]

Originally Posted by QuikSand

Ksyrup probably had the right idea.


I'm bumping this thread because I have done a little more reading on the topic, and again up against the measurement/existence precipice, and I once again am unable to make any more progress with my own intuition.

I understand the statements that learned people make about these topics -- it's not that I don't understand what people are saying ro claiming. I just am completely unable to process it as having real meaning.

Alas... thanks to those who, in this thread, have given me even more to think about. I am reaching the conclusion that I simply will never make intuitive peace with these concepts, and will have to come to terms with that. I appreciate the interesting contributions, though.

Are you caught up on the "can know velocity or location but not both" thing?

In our macro world, you have a baseball. You throw it and you can measure both it's velocity and location very easily. The act of observing it does nothing to baseball because it is so large.

To see something, you have to bounce light off of it. Photons will affect a baseball, but it is such a small amount that it isn't even worth measuring.

A particle of light bouncing off a tiny particle, however, alters it's trajectory so that it is no longer where you saw it last. That is how observation interfers. You know where the particle "was" at a particular moment in time but you can never really see it because seeing it (light bouncing off of it) alters its location so it is like you are chasing a ghost.

Horrible explanation, but it's the best way I was able to understand it.

[Mr. Wednesday]

It's weirder than that, really. The mathematical formalism is such that you can't simultaneously solve for two things that don't "commute". Momentum and position do not commute.

"Observation" seems to be a really slippery concept and I'm not sure even modern QM has pinned it down precisely. It's really not the same thing as having to modify the system to observe it, as I understand it.

[Mac Howard]

Originally Posted by QuikSand

I am reaching the conclusion that I simply will never make intuitive peace with these concepts, and will have to come to terms with that. I appreciate the interesting contributions, though.

I have this pet theory that the current resurgence of religion is caused precisely by this - that modern scientific theory is so seemingly anti-intuitive that the guy-in-the-street seeks other explanations. This theory received a boost only a couple of days ago when I watched a Discovery program E=mc2 which attempts to explain the derivation of the equation. It began by commenting that, in the 18/19th centuries, scientists were the pop musicians of the time - that scientific lectures were attended by the public as pop concerts are today.

Science in those days was relatively easily understood and the intelligent amateur stood a fair chance of being in touch with and understanding all the latest theories. But as science advanced and theories became more complex, mathematical and less linked to everyday experience the scientific world became increasingly isolated until today when much scientific understanding seems to make no (common) sense.

[Bonegavel]

Originally Posted by Mac Howard

I have this pet theory that the current resurgence of religion is caused precisely by this - that modern scientific theory is so seemingly anti-intuitive that the guy-in-the-street seeks other explanations. This theory received a boost only a couple of days ago when I watched a Discovery program E=mc2 which attempts to explain the derivation of the equation. It began by commenting that, in the 18/19th centuries, scientists were the pop musicians of the time - that scientific lectures were attended by the public as pop concerts are today.

Science in those days was relatively easily understood and the intelligent amateur stood a fair chance of being in touch with and understanding all the latest theories. But as science advanced and theories became more complex, mathematical and less linked to everyday experience the scientific world became increasingly isolated until today when much scientific understanding seems to make no (common) sense.

It's kind of like God made a bunch of wonderful laws for the macro world and left the quantum laws to his red-headed nephew that was always high on something.

[QuikSand]

Originally Posted by Bonegavel

Are you caught up on the "can know velocity or location but not both" thing?

In our macro world, you have a baseball. You throw it and you can measure both it's velocity and location very easily. The act of observing it does nothing to baseball because it is so large.

To see something, you have to bounce light off of it. Photons will affect a baseball, but it is such a small amount that it isn't even worth measuring.

A particle of light bouncing off a tiny particle, however, alters it's trajectory so that it is no longer where you saw it last. That is how observation interfers. You know where the particle "was" at a particular moment in time but you can never really see it because seeing it (light bouncing off of it) alters its location so it is like you are chasing a ghost.

Horrible explanation, but it's the best way I was able to understand it.

I'm fine with the whole thing as far as you take it. The idea that observation interferes -- got it, I can handle that.

It's the next step that just loses me -- the notion that of things like this (like the precise location and velocity of an item) cannot be measured, then essentially the item does not actually have a precise location and velocity.

It's not that I don't understand what I'm being told -- it's that I don't understand how that particular leap in logic makes any sense. To me, it simply does not. The co-called Copenhagen convention that equates immeasurability with non-existence is just beyond me.

I am aware that quantum theory very ably predicts phenomena that have been measured -- and so in this way it is constantly being verified or at least reinforced... so I presume that it is a truer explanation of realisty than my oversimplified understanding. I'm not saying it's wrong -- I'm just saying that I seem incapable of understanding it (and that is frustrating to me).

[QuikSand]

Originally Posted by Mac Howard

I have this pet theory that the current resurgence of religion is caused precisely by this - that modern scientific theory is so seemingly anti-intuitive that the guy-in-the-street seeks other explanations. This theory received a boost only a couple of days ago when I watched a Discovery program E=mc2 which attempts to explain the derivation of the equation. It began by commenting that, in the 18/19th centuries, scientists were the pop musicians of the time - that scientific lectures were attended by the public as pop concerts are today.

Science in those days was relatively easily understood and the intelligent amateur stood a fair chance of being in touch with and understanding all the latest theories. But as science advanced and theories became more complex, mathematical and less linked to everyday experience the scientific world became increasingly isolated until today when much scientific understanding seems to make no (common) sense.

Pretty interesting idea. There might be more there than I thought, on first glance.

[Bonegavel]

Originally Posted by QuikSand

I'm fine with the whole thing as far as you take it. The idea that observation interferes -- got it, I can handle that.

It's the next step that just loses me -- the notion that of things like this (like the precise location and velocity of an item) cannot be measured, then essentially the item does not actually have a precise location and velocity.

It's not that I don't understand what I'm being told -- it's that I don't understand how that particular leap in logic makes any sense. To me, it simply does not. The co-called Copenhagen convention that equates immeasurability with non-existence is just beyond me.

I am aware that quantum theory very ably predicts phenomena that have been measured -- and so in this way it is constantly being verified or at least reinforced... so I presume that it is a truer explanation of realisty than my oversimplified understanding. I'm not saying it's wrong -- I'm just saying that I seem incapable of understanding it (and that is frustrating to me).

It seems the Copenhagen interpretation (CI) only cares about the results of measurements.

In the 2 slit trick, for example, the CI only cares that there is an interference pattern created and doesn't give a hoot about how the single photon appears to have gone through 2 slits at once.

My readings show that Bohr's and company were very close minded about their CI and he would actually refuse to hear other interpretations.

Here is a quote from one of my source books (I too have been interested in this)

"It [Copenhagen interpretation] is a set of rules to abide by in order for us to make use of the quantum formalism without worrying about its meaning. Thus, not only does the Copenhagen interpretation not explain how the atom goes through the two slits, it states categorically that even to ask such a question is meaningless and we should restrict our comments to the interference pattern on the screen (the measurement)."

—Quantum, a guide for the perplexed by Jim Al-Khalili ©2003

I'm assuming here you are familiar with the 2 slit experiment.

Seems that Bohr's and company feel that only measurements matter. Trying to figure what is going on before the actual measurement is useless and it appears that this interpretation is favored by a majority of physists.

[Mac Howard]

Originally Posted by QuikSand

Pretty interesting idea. There might be more there than I thought, on first glance.

As the blues number goes "Don't start me to talking, I might tell everything I know".

There's a VERY big soapbox here. It starts with the parting of the ways of religion and science

[Mr. Wednesday]

Originally Posted by QuikSand

I'm fine with the whole thing as far as you take it. The idea that observation interferes -- got it, I can handle that.

It's the next step that just loses me -- the notion that of things like this (like the precise location and velocity of an item) cannot be measured, then essentially the item does not actually have a precise location and velocity.

Well, my conclusion, if I think about it hard enough, is that at the atomic level, particles do not have precise locations and velocities.

(With regard to the two-slit experiment... I would say that the single photon appears to have gone through two slits at once because it has gone through two slits at once.)

My take on QM, being nearly at the end of my first course on it, is that it seems daunting going into it but the mathematical formalism is surprisingly elegant.

[Mac Howard]

In the "Life Syllabus" thread I spoke of Bertrand Russell's "History of Western Philosophy" as a book that, for me, explains much that is difficult in philosophy so I decided to review what he had to say about Quantum physics to see if there was any enlightenment there. I think there may be. Here are some extracts dealing with relativity and Quantum Mechanics:

Common sense thinks of the physical world as composed of "things" which persist through a certain period of time and move in space. Philosophy and physics developed the notion of "thing" into that of "material substance", and thought of material substance as consisting of particles, each very small, and each persisting throughout all time. Einstein substituted events for particles; each event had to each other a relation called "interval", which could be analysed in various ways into a time-element and a space-element. The choice between these various ways was arbitrary and no one of them was theoretically preferable to any other.......

From this it seems to follow that events, not particles, must be the "stuff" of physics. What has been thought of as a particle will have to be thought of as a series of events. The series of events that replaces a particle has certain important physical properties, and therefore demands our attention; but it has no more substantiality than any other series of events that we might arbitraily single out. Thus "matter" is not part of the ultimate material of the world but merely a convenient way of collecting events into bundles.

Quantum Theory reinforces this conclusion, but its chief philosophical importance is that it regards physical phenomena as possibly discontinuous. It suggests that, in an atom (interpreted as above), a certain state of affairs persists for a certain time, and then suddenly is replaced by a finitely different state of affairs. Continuity of motion, which had always been assumed, appears to have been a mere prejudice. The philosophy appropriate to Quantum Theory, however, has not yet been adequately developed. I suspect that it will demand even more radical departures from the traditional doctrine of space and time than those demanded by the theory of relativity.

I think what this says is that, until we can get our heads around the idea of space/time and reject the "common sense" concept of reality as objects moving through space in a separate dimension of time, we will not be able to visualise the new description of the behaviour of reality. Our problem is that traditional philosophy has left us with a false model of reality that prevents us from seeing things in this new way

We are our experiences and "understanding" something means fitting it into these and describing it in terms of the familiar. Only when a space/time view of the world has become familiar will the descriptions be meaningful and "common sense".

I guess the question is "is this false model an inevitable consequence of our psychology or is it merely a question of replacing one concept which has become familiar with another?"

[QuikSand]

Originally Posted by Good ol' Bert

The philosophy appropriate to Quantum Theory, however, has not yet been adequately developed. I suspect that it will demand even more radical departures from the traditional doctrine of space and time than those demanded by the theory of relativity.

That puts it pretty well for me.

[dixieflatline]

Originally Posted by Bonegavel

It's kind of like God made a bunch of wonderful laws for the macro world and left the quantum laws to his red-headed nephew that was always high on something.

Wonderful laws in the macro world? Sorry, I'll take the quantum world any day. Six quarks, six leptons, four forces(two of which are already unified). It is that simple.

Quik, maybe this will help. Large colliders like at fermilab or CERN collide particles every day. This would be extremely boring if these particles interacted the same way every time. So what causes some events to produce one type of particle and other events to produce something else? The particles don't know what they are going to form until it happens, similiarly, the particles don't know exactly where they are or what their velocity is until it is required. Eh, maybe it won't help so much.

[Bonegavel]

Originally Posted by dixieflatline

Wonderful laws in the macro world? Sorry, I'll take the quantum world any day. Six quarks, six leptons, four forces(two of which are already unified). It is that simple.

That simple? Einstein couldn't figure this shit out and he was a dummy compared to some of these other guys that can't figure it out.

[Mr. Wednesday]

It's ironic, because as I understand it Einstein's work on the photoelectric effect was one of the experimental underpinnings for QM.

I think the problem wasn't that Einstein didn't understand it. The problem was that he refused to accept it.

[Mac Howard]

Originally Posted by QuikSand

That puts it pretty well for me.

ol' bert did write that in 1946 or earlier and one would have hoped that someone would have come up with a "common sense" explanation by now - though I haven't seen one. It still seems that it's necessary to be competent in the appropriate mathematical areas to 'understand" Quantum Theory.

[Mr. Wednesday]

The basic math of introductory quantum mechanics is a single partial differential equation. Even if you haven't actually studied the math, as long as you can handle calculus (which is really also necessary to handle classical mechanics), I assert that you can learn the math required to solve the PDE.

[Mac Howard]

I was doodling on Google and came across this:

http://plato.stanford.edu/entries/qt-idind/

Interesting .................................... if you have a few hours to spare

[QuikSand]

Originally Posted by Mr. Wednesday

The basic math of introductory quantum mechanics is a single partial differential equation. Even if you haven't actually studied the math, as long as you can handle calculus (which is really also necessary to handle classical mechanics), I assert that you can learn the math required to solve the PDE.

For me, though, it's not about the math. Even if I could revive enough calculus to be able to solve an equation (I suppose the wave equation describing the probabilistic location function for matter, for starters?) it's not the math that's getting in my way of appreciating the concept.

It's the concept itself.

Last night, I re-listened to a couple of the lectures from the series that sparked this thread for me, and I had a little bit more luck with the idea of super-positioning. Conceptually, I think I'm closer to understanding how that is believed to work than I had been before (after doing a litle reading between my first and second listen to that particular lecture).

As I am beginning to understand it, the particle/wave duality of matter (a concept that starts off very alusive to me, but I'm trying to give it a fair shake) essentialy states that the actual location of a particle is not really defined (as we would think of it) until it is measured (and with measurement, we know we introduce uncertainty in either location or velocity, thanks to Heisenberg). Instead, its location is essentially just a probabilistic function that may indeed have multiple possible consistent answers. The lecture described an electron that may be in one of two possible orbits... is it in the lower orbit or the upper orbit? The answer is basically that we can't say -- it's actual position is not definable that way, but rather it's just likely to be found in the two orbits according to this probabilistic function. If we go searching for it and use some detection device, the probabilistic function will determine where we are most likely to locate it in a physical sense, but by doing so (and isolating a specific location) we corrupt its previous wave state (that generated the location uncertainty) and have in fact interfered with the particle.

Or something like that. I hope that paragraph above makes some sense... because to me, it's been a fairly long time coming. (If I actually have made a meaningul stride in "getting" this idea)

[Mr. Wednesday]

Your paragraph is in accord with my understanding of things.

That also touches on the idea (that I find to be quite slippery) of wavefunction collapse -- when you precisely locate a particle, it no longer has a probabilistic wavefunction, instead the part that describes its location turns into a Dirac delta function.

[Mac Howard]

Originally Posted by QuikSand

As I am beginning to understand it, the particle/wave duality of matter (a concept that starts off very alusive to me, but I'm trying to give it a fair shake) essentialy states that the actual location of a particle is not really defined (as we would think of it) until it is measured (and with measurement, we know we introduce uncertainty in either location or velocity, thanks to Heisenberg). Instead, its location is essentially just a probabilistic function that may indeed have multiple possible consistent answers. The lecture described an electron that may be in one of two possible orbits... is it in the lower orbit or the upper orbit? The answer is basically that we can't say -- it's actual position is not definable that way, but rather it's just likely to be found in the two orbits according to this probabilistic function. If we go searching for it and use some detection device, the probabilistic function will determine where we are most likely to locate it in a physical sense, but by doing so (and isolating a specific location) we corrupt its previous wave state (that generated the location uncertainty) and have in fact interfered with the particle.

Or something like that. I hope that paragraph above makes some sense... because to me, it's been a fairly long time coming. (If I actually have made a meaningul stride in "getting" this idea)

I think that's about as good as it gets when the concepts have no parallel with our everyday experiences - we can reproduce the words reliably with some understanding of what they mean but with little satisfaction that we fully understand. Eventually, I guess it becomes sufficiently familiar to be accepted as understood. Do we really understand Newton's Gravitational Field as anything other than a useful construct? I recall telling my physics teacher that I didn't believe him when first told of it but it's become familiar enough that I now think I do.

A couple of days ago I read an article on Heisenberg's Uncertainty Principle explaining the disagreement on its publication between Heisenberg, Einstein and Bohr. The author insisted that you have to accept that entities involved in quantum events are both particle and wave simultaneously. He grants that the two are normally mutually exclusive and that considering an entity as two different things at once is problematical. However he makes no attempt to explain why or what considering them as both means. It seems enough to accept the idea even if it does seem nonsensical as long as it leads to an "understanding" of the overall concept.

I recall hearing a lecture some years ago, I think it was Feynman, who joked about a fellow physicist that he was "one of the 15 people in the world who understands quantum mechanics". That does it for me

[Mac Howard]

I was watching the second part of the E=mc2 program last night and was surprised to see that something similar to our problem with quantum mechanics occurred with the concept of energy.

Newton introduced the idea of force (itself not an easy concept to visualise) - that which caused a body to change velocity. The question arose "what potential does a moving body have for imposing a force on another body?". Newton, and later Descartes, insisted that the potential was directly proportional to the mass and the velocity - effectively the momentum mv of the moving body.

But it was Leibnitz who argued for a "vis viva", or life force, that was dependant on the SQUARE of the velocity and not a linear relationship. He was ridiculed for this - accused of reintroducing supersticious ideas into the newly confident scientific world. Of course Leibnitz's "vis viva" we now know as "energy".

But it took the scientific community over 100 years before it accepted this idea, despite mounting evidence from experiment that it was correct.

Why? Well the idea of energy is anti-intutive. If a force increases the velocity of a body linearly then surely the velocity of the moving body has a linear effect on other bodies? It simply seems more intuitive that the velocity will be the determing factor. Where does the square of the velocity come from?

Even now I can't think of any conceptual "reason" why it should be the square. I just accept it is. The evidence from experimentation says it is and the mathematical equation 1/2mv2 (one half mass times velocity squared) coming out of experimentation says it is. After so much repetition it has become so, not because of any really convincing non-mathematical conceptualisation.

So, understanding energy held a similar problem for 18/19th century scientists as the concepts from quantum mechanics has for us today (though we now have more sense that to ridicule it) and the concept eventually became accepted because of experiment and familiarity despite the fact that it is still a little on the anti-intuitive side.

Of course Einstein came along and showed that energy is really an increase in mass where increasing the velocity of a body increases its mass by E/c2 (I think have that right but Einstein is still a problem for me )

I find that easier to understand when it comes to thinking in any depth of what the two (energy or increase in mass) mean - you push a body and, instead of taking on some nebulous quantity called "energy", it increases in mass.

[QuikSand]

There's a lecture tonight in Annapolis than I'm planning to attend:

http://www.stjohnscollege.edu/asp/ne...l.aspx?hid=334

The Quantum World Explained at St. John’s College


David Branning, assistant professor of Physics at Trinity College, Hartford, Conn. will talk on “Quantum Mechanics.” The lecture, which is free and open to the public, will be held in the Francis Scott Key Auditorium on Friday, November 10, at 8:15 p.m.

“Quantum mechanics is the most successful physical theory ever created, but it insists that there is randomness and uncertainty at the most fundamental levels of nature,” says Branning. “I will discuss a ‘thought experiment’ that led Einstein to conclude that quantum theory is not a complete theory, and the related experiments, based on Bell's inequality, that have been carried out in the laboratory since then.”

Branning is a member of the Optical Society of America, the American Physical Society, and the New York Academy of Sciences. His research interests focus on quantum optics, including single-photon and two-photon interferometry, tests of nonlocality and the foundations of quantum mechanics, parametric downconversion, and quantum information processing using the polarization and/or spectral degrees of freedom for photons.

I'm looking forward to it, though I suspect it won't do much to resolve my own frustrations with the subject.

[rkmsuf]

I'm currently reading The Elegant Universe by Brian Greene.

I highly recommend it if you are into quantum mechanics or *gasp* string theory.

Doesn't bury you in math...kind of takes an approach most can grasp.

I think this book was also made into a NOVA special as well.

[QuikSand]

Originally Posted by rkmsuf

I'm currently reading The Elegant Universe by Brian Greene.

I highly recommend it if you are into quantum mechanics or *gasp* string theory.

Doesn't bury you in math...kind of takes an approach most can grasp.

I think this book was also made into a NOVA special as well.

I second the recommendation for all of the above. It puts all these items into a fairly approachable level.

[Maple Leafs]

Does anyone else ever see a bumped thread like this, notice the black dot, and think "What in the hell could I have possibly contributed to that thread? Man, I hope I didn't just make some smart-ass one-line post..."

[Mr. Wednesday]

Originally Posted by QuikSand

There's a lecture tonight in Annapolis than I'm planning to attend:

http://www.stjohnscollege.edu/asp/ne...l.aspx?hid=334



I'm looking forward to it, though I suspect it won't do much to resolve my own frustrations with the subject.

FYI, the Wikipedia entry on Bell's Inequality:
http://en.wikipedia.org/wiki/Bell%27s_inequality

[TurnerONU22]

As a chemistry grad student in my first year, I hear all of the Physical division complain about their quantum mechanics classes. Although, as wanting to do computational chemistry, I will have the pleasure of auditing those classes next year, which will be tolerable since I don't have to take the exams. I'm actually excited to dig into that stuff some more, because in undergraduate physical chem classes, you're only introduced to a small amount. With the computational chemistry, it is based on all the quantum mechanical equations to depict where the electrons can be, and how the energies of molecules can be found due to these.

Though I do have to throw the Heisenberg joke in here: Heisenberg was out for a drive one day, when he's stopped by a traffic cop. The cop says: "Do you know how fast you were going?" Heisenberg replies "No, but I know where I am."

[Mr. Wednesday]

At ND, there are grad level stat mech and quantum mechanics courses offered in the chemistry department -- I took both.

[TurnerONU22]

Originally Posted by Mr. Wednesday

At ND, there are grad level stat mech and quantum mechanics courses offered in the chemistry department -- I took both.

Yeah, at Ohio State, we already have five first years changing from Physical to Analytical just because they can't handle the Quantum class. Luckily, since I will audit it next year, I don't have to worry about grades for that.

[JeffW]

Originally Posted by QuikSand

On Heisenberg and the clockwork universe...


I have been trying to educate myself a bit on modern physics – a subject that I find generally interesting, despite having dropped off the real-sciences academic track many years ago.

Check out Q.E.D. by Richard Feynman. It's an excellent, technically accurate but accessible book that covers some of the interesting features of quantum mechanics.

Anyway, in the lectures, we are presented with Heisenberg’s well-known uncertainty principle, basically with a promise that this would help us out of this particular conundrum.

Okay – here’s where I have trouble. In my mind, I still want to say something like this:

[b]Fine, we can’t measure everything, so we won’t be able to know where things are and how they are moving. But they still are somewhere, and they still are moving, right? So they still do, in fact, have all those various physical interactions with one another, even if we cannot measure them in any practical way.

I only have a B.S. in Physics, but my understanding is that the common belief among physicists today is that particles don't actually have a definite position or velocity, that they really are probabilistically "spread out" across all velocities and positions. The opposing view is that particles do have a definite position and velocity, but we have no way of measuring them without disturbing them.

There is no way to resolve this discrepancy right now, but either way I think the problem of a clockwork universe stands unless you believe in forces which we cannot measure that are acting to give us free will. At the most basic level, our actions are determined by either the random or deterministic actions of subatomic particles. Either way, we don't have control over our actions.

Also, one thing I think I forgot to quote is your statement that "Measurements tend to disturb the system." The fact is that measurement is disturbance. There is no difference between the two. Think about what happens when you look at someone--information about their appearance is carried by light particles that "hit" them, thus disturbing them.

[WVUFAN]

I like lamp.

[cartman]

I was reading the following article, and was reminded of this thread. The theory they postulate here is WAY beyond what I can comprehend. A group of astrophysicists believe we may have reduced the lifespan of the universe, simply by observing a possible source of dark energy. Interesting stuff.

http://www.news.com.au/adelaidenow/s...005962,00.html

Honey, I doomed the universe

ASTRONOMERS may have unwittingly hastened the end of the Universe by simply looking at it, according to a theory reported in the latest edition of New Scientist.

The novel idea is being aired by two US physicists, who attack the notion that the universe, believed to have been created in the "Big Bang'' some 13.7 billion years ago, will go on, well, forever.

In fact, the poor old cosmos is in a rather delicate state, they say.

Until recently, a common idea was that the energy unleashed in the Big Bang happened when a "false vacuum'' - a bubble of high energy with repulsive gravity - broke down into a safe, zero-energy "ordinary'' vacuum.

But recent evidence has emerged that places a cosmic question-mark over this cosy thought.

For one thing, cosmologists have discovered that the Universe is still expanding.

And, they believe, a strange, yet-to-be-detected form of energy called dark energy pervades the universe, which would explain why the sum of all the visible sources of energy fall way short of what should be out there.

Dark energy, goes the thinking, is a result of the Big Bang and is accelerating the universe's expansion.

If so, the universe is not in a nice, stable zero-vacuum state but simply another "false vacuum'' state that may abruptly decay again - and with cataclysmic consequences.

The energy shift from the decay would destroy everything in the universe, "wiping the slate clean", says Lawrence Krauss of Case Western Reserve University in Cleveland, Ohio.

The good news is: the longer the universe survives, the better the chance that it will mature into a stable state. We are just beyond the crucial switching point, Mr Krauss believed.

The bad news is: the quantum effect, a truly weird aspect of physics that says whenever we observe or measure something, we reset its clock.

Mr Krauss and colleague James Dent pointed to measurements of light from supernovae in 1998 that provided the first evidence of dark energy.

These measurements might have reset the decay clock of the "false vacuum'' back to zero, back before the switching point and to a time when the risk of catastrophic decay was greater than now, said Mr Dent and Mr Krauss.

"Incredible as it seems, our detection of the dark energy may have reduced the life expectancy of the universe,'' said Mr Krauss.

"We may have snatched away the possibility of long-term survival for our universe and made it more likely it will decay.''

The report says the claim is contested by other astrophysicists and adds reassuringly: "The fact that we are still here means this can't have happened yet.''