Delayed Choice Quantum Eraser

The observer has not the ability to classically measure quantum properties. The dual nature of particles does not allow you. You do not change the properties by simply looking at them, that's magic. I can understand philosophers grasping at this like kids in sweet shop but lets not stuff ourselves with probabilities and call it reality.

Or maybe the philosophers are not as ignorant as you think they are and you are just not seeing the subtleties of their points?

The issue isn't between probabilities or certainties because science only deals in probabilities anyway. And on the subject of observer relative reality, I would argue independent of any scientific theory, that reality is observer relative. Making a metaphysical argument is anything but "magic." You keep tossing that word around, but I have yet to see you put forth any philosophical arguments.

If my explanation is not sufficient for you to grasp my point of view, sorry but there is nothing else to add. You may believe your observer reality is different to mine but as you have never experienced my reality , how can you tell? If the QM world is built of probabilities why do keep insisting it is observer controlled and everything is indeterminate. I am only assuming it is not proved but you insist it is.

Acts of observation (and all other acts) always affect the things being observed, regardless of Quantum Mechanics and various philosophical interpretations thereof. It's just that, before quantum mechanics, it was assumed that the effect of the observation could always be made arbitrarily small. (That is, for any given effect, it's always theoretically possible to make the effect smaller.) The contribution of QM was to show that this is not so. The observer can never be thought of as wholly separate from the world being observed.

I wonder if quantum particle's behavior depends on observer of any kind of mental strength, for example will it act the same if a mentally handicapped person looks at it? I mean: does quantum particle react only to scientific mind, or any other human mind, or to the observations of a monkey and other animals as well?

Acts of observation (and all other acts) always affect the things being observed, regardless of Quantum Mechanics and various philosophical interpretations thereof. It's just that, before quantum mechanics, it was assumed that the effect of the observation could always be made arbitrarily small. (That is, for any given effect, it's always theoretically possible to make the effect smaller.) The contribution of QM was to show that this is not so. The observer can never be thought of as wholly separate from the world being observed.

I wonder if quantum particle's behavior depends on observer of any kind of mental strength, for example will it act the same if a mentally handicapped person looks at it? I mean: does quantum particle react only to scientific mind, or any other human mind, or to the observations of a monkey and other animals as well?

Just try measuring a child's smile and they would lock you up. Tell me your gaze has power to alter reality and I will lock you up.

If my explanation is not sufficient for you to grasp my point of view, sorry but there is nothing else to add. You may believe your observer reality is different to mine but as you have never experienced my reality , how can you tell? If the QM world is built of probabilities why do keep insisting it is observer controlled and everything is indeterminate. I am only assuming it is not proved but you insist it is.

There are similarities and differences. How do I know? Because our experiences are part of the same phenomena.

The point is that there is no such thing as a completely passive observer. An observer occupies space, emits radiation, absorbs photons of light that would not otherwise have been absorbed etc. The effect on the thing being observed may be vanishingly small and difficult to quantify (because it's impossible to rewind time and see how the world would have behaved without the observer in it) but it's not possible to completely remove it.

On a wider point, to be honest I don't think the discussions here about quantum mechanics serve much purpose because they mostly seem to be uninterested in actual experimental evidence and more interested in everyday experiences. It's the "if I can't see it in my living room it doesn't exist" school of thought. Some aspects of the the way the universe works are a very very long way from direct human experience. That doesn't mean they don't exist.

There's nothing wrong with not understanding a subject. I just don't see the point of discussing it in that context and insisting that it makes itself clearly easily understandable and visible to me in my everyday life without any effort on my part to learn about it.

The point is that there is no such thing as a completely passive observer. An observer occupies space, emits radiation, absorbs photons of light that would not otherwise have been absorbed etc. The effect on the thing being observed may be vanishingly small and difficult to quantify (because it's impossible to rewind time and see how the world would have behaved without the observer in it) but it's not possible to completely remove it.

On a wider point, to be honest I don't think the discussions here about quantum mechanics serve much purpose because they mostly seem to be uninterested in actual experimental evidence and more interested in everyday experiences. It's the "if I can't see it in my living room it doesn't exist" school of thought. Some aspects of the the way the universe works are a very very long way from direct human experience. That doesn't mean they don't exist.

There's nothing wrong with not understanding a subject. I just don't see the point of discussing it in that context and insisting that it makes itself clearly easily understandable and visible to me in my everyday life without any effort on my part to learn about it.

I agree with you that there are two levels of discussion here. One is a purely scientific inquiry into what is the nature of either the scientific consensus on what interpretation there is in regard to Quantum mechanics and subsequent experiments. The other is philosophical.

No amount of scientific evidence will address the philosophical concern because it is at a level of inquiry that is beyond the scope of the limits of the scientific method. So when you say something like the world is existing on its own when no one is observing it, you are making a philosophical and specially metaphysical statement, particularly the school of thought is known as realism.

Of course a scientist can be consistent in talking about unobserved objects but this is purely pragmatic and the scientist is not committed in ANY way to holding such a view. In fact, ALL scientific data can be interpreted philosophically to be one way or the other because, as I said, such questions are beyond the scope of what the scientific method can answer.

However, simply because they are beyond the scope of the method does not mean that they can never be answered or that they don't exist. It is simply the case that they must be answered philosophically.

On the delayed choice experiment, the point I was making is that the Copenhagen interpretation is the prevailing one, at least so far. What do you think of that interpretation?

You do it again and again exogen admit that QM is not relevant but then quote it as if it can prove some strange notion. You will not accept observable evidence but can argue for an unproven, unobservable concept. A concept that the observer can alter an event, has no value unless you can give an example other than your constant reference to a vague QM theory.

Exogen,

I'm compelled to point out that although 90% and more of physicists subscribe to the Copenhagen Interpretation only as some sort of "default" position, that is, not through any philosophical "commitment," Neils Bohr himself definitely saw it as a philosophical position. I've read only a little bit of his own words on the matter, and more on his Principle of Complementarity, which he felt was a necessary part of the Copenhagen Interpretation, though most people don't think so.

From what I read, Bohr's position seems to be in kinship with Positivism--not the logical positivism of Bohr's contemporaries (e.g., Carnap, Ayers, etc.) but the 19th century variety of Comte. There are some scientists who embrace Positivism expressly--Stephen Hawking is probably the most visible. I think Positivism is a potentially dangerous and naive philosophy myself, and is one of the factors that has led to Bioethics as a reaction to it.

A poster he or I,

let me be clear, I was not suggesting any reasons why the Copenhagen interpretation is widely accepted. Dennett is a something of a positivist insofar as he subscribes to a strict verificationism.

Xris,

I am bracketing knowledge. When I talk about what the current scientific consensus is, say on Quantum Mechanics, I am speaking about it within the domain of what science. When I am talking outside that domain I am arguing philosophically. There is nothing inconsistent about doing that.

Let me ask you this, what exactly constitutes "proof" in your view?

If Comte can be anything of hero then his notion that we can only be privileged to certain information must infer we accept our senses and believe in our observable universe. To stray from the path of positive understanding we need to secure another theory that can stand the rigours of examination. I do not doubt the sincerity of the quantum theorists but I doubt their conclusions. When we step on new shores, do not believe we understand what lies beyond, in the hinterland.

If Comte can be anything of hero then his notion that we can only be privileged to certain information must infer we accept our senses and believe in our observable universe. To stray from the path of positive understanding we need to secure another theory that can stand the rigours of examination. I do not doubt the sincerity of the quantum theorists but I doubt their conclusions. When we step on new shores, do not believe we understand what lies beyond, in the hinterland.

But you doubt their conclusions based on your own metaphysical presuppositions, namely that every event is causally determined. On the issue of empirical data, our senses just tell us that stuff is happening. Why it is happening and what it is, is another story. The best science can do is use theories to explain the data in a coherent and understandable way and make predictions for future observations. But none of that shows anything to be true metaphysically, it is purely functional in terms of predicting patterns.

This notion of causality is itself an empty shell in light of this because the only causality science has is a virtual one without any metaphysical presuppositions.

Exogen:

On the delayed choice experiment, the point I was making is that the Copenhagen interpretation is the prevailing one, at least so far. What do you think of that interpretation?

I don't think the delayed choice experiment, as you described it earlier, if carried out, would give the results you describe. You seemed to be saying, if I remember rightly, that if, for example, a double slit experiment of some kind were carried out with, say, electrons, and if the slit through which the electrons passed was recorded but not revealed, then the statistical behaviour of the electrons as they hit the screen (i.e. the interference pattern) would be affected by the delayed observation or disposal of the recorded results. you seemed to be saying that observing the results, even at some great distance away, would instantly change the behaviour of the electrons and the pattern on the screen. I'm a bit rusty on all this, but I'm pretty sure this simply isn't true.

The change to the behaviour of the electrons as they pass through the slits is caused by the electrons being observed. But this isn't a statement about the consciousness of the observer. It's simply a statement about the fact that electrons are small and easily perturbed by, say, photons. If you use photons to "observe" the position of the electrons then it is the collision of a photon with an electron that constitutes the act of observation. I think, to be honest, you may actually be imbuing QM with more metaphysical mystery than it deserves.

Steve,

As I understand it the whole point of why they called it the delayed choice double slit experiment is that the choice to look at the data or not and then observe the pattern determines the outcome. Its really just an example of the cat in the box.

Edit: not that this is the best source or anything but I just looked it up on Wikipidea and it talks about Wheeler and his origional thought experiment which was later supposed to be confirmed that in fact it is the observer that is effecting the outcome. Here is the link. I will see if I can find more official sources in the meantime.

http://en.wikipedia.org/wiki/Wheeler%27 ... experiment

There are alternative theories concerning the double split experiment. String theory suggests that atoms are tied together with entwined strings or ropes and what you appear to be seeing is something else entirely. It has nothing to do with waves or particles expressed as electrons in the conventional concept of atoms in the double split experiment. Place one object in their path and you still see a distortion pattern so how is that explained? Science is in conflict, competing theories and the careers of their proponents are battling for our votes.

I will not accept quantum science as a reason to change my perspective on our universe till a fully agreeable and understandable logic has emerged.

Xris,

well the Copenhagen interpretation is dominant and has been dominant for over half a century, so I don't know how much more agreeable things can get.