The observer

[Kygron]

I just read in Lee Smolin's new book about the problem with the observer in Quantum physics. He called it one one the 5 biggest problems, that you need an observer for it to work out right.

 

Is this really a problem????? I had always assumed it was the way you explain a non-problematic but unique situation to a non-physisist. Would the whole theory really break down if we all "shut our eyes"?????

[daniel_haxby]

(Disclaimer: pop science/non-expert answer!)

 

It makes it a bit difficult to have faith in a deterministic universe.

 

Even if everyone has their eyes open, a vast amount happens far away in the universe that we cannot observe. You may suppose this doesn't affect us, since to affect us, we'd observe its effect, and then we wouldn't have a deterministic quandry.

 

But consider a closed box, weighing mass M, and opaque to every force we can detect. Imagine if it opened. What would come out? We start observing the interior of the box, and so this mess of quantum superposition breaks down to some definite answer. But why should the answer it gives make any sense at all? Anything could be in there, and not just anything we could predict or conceive of.

 

In an objective universe, when a photon comes flying out of the distances of the universe, we learn something about possible future photons. But if the universe can do whatever it wants to when we're not looking, what's the point?

[Edtharan]

the problem with the observer in Quantum physics

Yes, the Observer is a big problem in QM, but not for the reason that you think. The problem is that people think that when they say "Observer" then mean a "person".

 

This is not the case. By "Observer" they mean "Any outside thing that can interact with the system under question".

 

Once you understand this, there is no problem. The "Observer" can be an electron, a photon, and so forth.

 

So even if we "Shut our eyes", even if we didn't exist, there would still be interactions going on, and thus there would be "Observers".

[fredrik]

The concept an observer in QM is indeed important, because the formalism of quantum mechanics really singles out a particular observer. IMO this is sign of slight incompleteness that is on the todo list. While the concept of a single observer is sound and unavoidable, the missing part is the proper observer invariant formulation of QM, or rather the explicit observer to observer transformations. This is not the same thing as a plain spacetime transformation, it is a transformation also over the "set of all possible a priori conditions".

 

Like Edtharan writes, "observer" means the point of view on which reality is projected. But the point is also, that in some domains the observer is also affected. The observers information, or a priori given information, is the condition of his probability estimates. But these things change.

 

Loosley speaking I like to think of "observe" and "interact" as pretty much synonyms.

 

If we "shut our eyes", it means we disconnect ourself from the system, and thus stops interacting, and thus does not receive further information whatsoever. We simply loose our reference and connection.

 

You can say that an electron is "observing" the nucles in an atom, and the nucles is "observing" the electron field.

 

I think the reformulation of QM that is needed (sooner or later) need to more definitely address the status of the observer, and define transformations to arbitrary observers.

 

In the complete formulation I would like to see, ALL the a priori information implied by an observer, beeing explicitly put into the equations of physics. And I suspect this theory will be very much like a information theory. My personal hunch is that, that path is that way to go to get a proper resolution to this.

 

/Fredrik

[fredrik]

Of course in reality, we can't stop observing. "Closing our eyes" taken, litteraly would mean we are "ingnoring" input - which is simply ignorance. And QM does not model "ignorant" observers.

 

/Fredrik

[fredrik]

I see an analogy here with the past.

 

Einstein realised the problem of "doing physics" in a spacetime reference - the problem beeing that the spacetime itself should really be part of the dynamics. Ie. our reference changes during interactions.

 

Now we have a similar story. We try to do probability theory given fixed a priori conditions. I think it is similarly clear that the same way spacetime is not really a fixed reference, neither is our a priori information. Ie. our a priori information changes during interactons.

 

IMO, the probability theory is in a certain sense more fundamental than spacetime. When we do QM, not only does spacetime itself change, but also our a priori information.

 

Einstein made use of his gedanken experiments with different observers. QM now puts another layer of abstraction ontop of this. And care must be taken not only when comparing spacetime transformed observers, but also that these observes may have completely different a priori information. Making it a qualified mess, since the "in absurdum"-quantization is done on a specific spacetime, but it's clear already at this philosophical level that this is sort of a quasi procedure that isn't obviously correct.

 

So far I think it's relatively clear. What is needed is a new formalism to handle this. And to combine both GR and this new formalism into a consistent framework is the challange. Observer concept is indeed central to this as well.

 

/Fredrik

[fredrik]

IMO, I think to talk about probability as it if was universally objective, without defining your a priori constraints is just as reasonable(or unreasonable) as it is to talk about velocity without defining the spacetime reference. And to talk about observed reality without defining the observer. What is very likely, almost to the point of beeing a fact, to me may be utterly unlikely to someone else almost to the point of beeing close to false, and there is no contradiction in that.

 

This is assuming you take the standpoint that true is rather the limiting case of probability approaching 100%, and false beeing probability approaching 0.

 

I'm sure some mathematicians may have objections to this terminology but then again, I guess we are all still looking for a satisfactory formalism.

 

/Fredrik

[Kygron]

Yes, the Observer is a big problem in QM, but not for the reason that you think. The problem is that people think that when they say "Observer" then mean a "person".

 

This is not the case. By "Observer" they mean "Any outside thing that can interact with the system under question".

 

Once you understand this, there is no problem. The "Observer" can be an electron, a photon, and so forth.

 

So even if we "Shut our eyes", even if we didn't exist, there would still be interactions going on, and thus there would be "Observers".

 

Yes, this is the way I thought it was. The book seemed to make a bigger deal about it in my mind. You say "there is no problem" and I would agree, assuming the rest of what you said is true and complete.

 

So why then does Smolin rank it as the second biggest problem in physics, after unification of theorys??

[BhavinB]

Fredrik really has a good knack at conveying his thoughts and providing a unique perspective.

 

Fredrik: I enjoyed reading your posts on this 'observer issue'.

[fredrik]

So why then does Smolin rank it as the second biggest problem in physics, after unification of theorys??

 

I can't comment on Smolin or the book because I didn't read it, but IMO the observer is an important and fundamental ingredient in unification is the observer status.

 

My general attitude is that diverse thinking is excellent, and instead of debunking each others thinking, we should encourage diversity in thinking. I see several ways of attacking this, and even though I have placed my bets, I think there isn't such a thing as wrong thinking here. Just more or less akward But then if someone wants to go akward, why not. And maybe the bigger point - I really am not the one to tell what is akward for someone else. I speak only for myself.

 

IMO, you can spend alot of thinking on this basic stuff too... and in a certain

sense it takes you all the way to the axioms of logic. I think that we should acknowledge our probable incompleteness here because we are not gods and instead focus on making the best possible progress, given our capability. This is a fuzzy problem and can not possibly be solved in the realm of trigonometry.

 

I put high emphasis on the logical foundations, axioms and philosophy. Because this is really what is approves any formalism used. There are other strategies that others are working on. I suspect the strategy or philosophy depends on wether you consider the observer to be a big problem or not.

 

Without having read his book, if smolin puts the obserer in the top list, it makes great sense to me.

 

/Fredrik

[fredrik]

Thanks BhavinB.

 

Your "appreciating" feedback is an interesting. My experience is that sometimes these things are hard to discuss. Because sometimes new problems requires talking beyond the standard formalism, and thus we get into communication issues. In particulary in a group of people with different backgrounds that use terminology in different ways. The narrow minded people tend to reject the communication because they can't detect the formalism. But that is exactly part of the problem. But sometimes there is disagreement, and and that point the talking is a waste of time.

 

I know of people who hold completely different points of views, and has the mindset that all this philosophy talk is basically "beyond the point" and should be left aside, and have other ideas how to make progress. And in a certain sense, I can see the other ways, but they are just incompatible with my mindset, so we don't work for me. I think we are all different and solve problems in slightly, at least apparentely, different ways. The proof is in the success. I have accepted that the progress itself is, and *has to be* a little fuzzy.

 

/Fredrik