Argument in QM.

[Thinker]

I have a question about observance. I am reading a book called "The Trouble With Physics" by Lee Smolin, and he adresses a "problem" with Quantum Mechanics: The point that you put a boundary between you and the observer by being the observer, which is usually ok exept for the fact that your observing has an effect on the experiament itself, and I think the point he was trying to make was that if you expand the observation to someone watching the experiament then they become the observer and the person doing the measurements and the atoms themselves become the sytem onserved. I guess he has a problem with a theory that is based on what effect we have on something, and therefore an either incopleteness in the fundamentals of QM, or altogether wrong. First off is this a valid point? and second if you base a theory on what effect we have on something if we can prove that we covered all the bases then why should it be incomplete?

thanks

 

Thinker

[BenTheMan]

The point that you put a boundary between you and the observer by being the observer, which is usually ok exept for the fact that your observing has an effect on the experiament itself, and I think the point he was trying to make was that if you expand the observation to someone watching the experiament then they become the observer and the person doing the measurements and the atoms themselves become the sytem onserved. I guess he has a problem with a theory that is based on what effect we have on something, and therefore an either incopleteness in the fundamentals of QM, or altogether wrong.

 

I don't know what exactly Smolin is talking about, but this doesn't sound like physics...it sounds much more like philosphy. The act of ``observing'' is usually just an interraction between a probe and a process. The probe carries information away from the process. In some sense, Smolin is trying to show a reductio ad infinitum---he's trying to show a paradox that you can always find a closer observer. There's no real paradox, as Smolin would agree, because there is a fundamental length scale in nature.

[Martin]

I have a question about observance. I am reading a book called "The Trouble With Physics" by Lee Smolin, and he adresses a "problem" with Quantum Mechanics...

 

Hi Thinker.

I have the book, which I've read a lot and like. It makes some important points.

So I'd be delighted if you would say WHAT PAGE you are talking about. Then we could both be looking at the same page and could discuss more clearly.

 

For starters, without even referring to what Smolin says about it, I can respond in a general way. YES the problem of the observer is a widely recognized problem with quantum mechanics that a lot of people have talked about. One place it kicks in especially hard is where you are trying to formulate a quantum cosmology---a quantum theory of the universe.

 

Because in the conventional formulation of quantum mechanics there is a quantum system being studied and a classical or NON-quantum observer. The world is divided in a kind of schizophrenic way between on the one hand a system that obeys uncertainty and is described by a wavefunction and probabilities, and on the other hand a classical thing called an observer that is not governed by uncertainties and is not described by a wavefunction.

 

this is a fundamental inconsistency in how conventional QM pictures the world, one piece is classical observer and the other piece (in an imaginary box) is quantum experiment.

 

For most purposes this is OK and easy to live with, but when you want to have a quantum state of the UNIVERSE then what box do you put it in and where is the observer going to stand?

 

There has been lots of thinking by lots of people about this and much writing. One discussion I remember particularly is in Carlo Rovelli's book "Quantum Gravity" published by Cambridge, but that's just one of many.

 

the easiest way to satisfy both my curiosity and yours would be if you give me a page reference to Smolin's book and I see exactly what your are asking about

 

thanks