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Another short question.


Just Some Guy
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So I'm trying to clarify in my head a better idea of the observer, and how it fits into relativity and quantum mechanics, but I'm not finding the info I need scattered about. Anyone mind just giving me whatever rundown you think fits the question, and/or if there's any equations that directly relate?

Edited by Just Some Guy
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So I'm trying to clarify in my head a better idea of the observer, and how it fits into relativity and quantum mechanics, but I'm not finding the info I need scattered about. Anyone mind just giving me whatever rundown you think fits the question, and/or if there's any equations that directly relate?

 

Do you have a specific question?

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Not a specific one, no. I just can't wrap my mind around how it fits into already established theories like quantum mechanics and relativity.

 

Something like just saying "this is how it's defined in relation to ______." And yes, I do realize this is a strange question.

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In relativity an observer is just a coordinate system. It's sort of a lattice of rulers and clocks.

 

In quantum mechanics, it's something that collapses the wave function. It could be, for example, a detector that uses EM radiation.

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For QM, just think of an observer as something that interacts with the system. If a particle hits a brick wall, the wall has "observed" the particle.

 

It's not a perfect analogy, but it's closer than the image most people bring up in their minds when they hear the word 'observer' used in quantum mechanics.

Edited by Delta1212
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So I'm trying to clarify in my head a better idea of the observer, and how it fits into relativity and quantum mechanics, but I'm not finding the info I need scattered about. Anyone mind just giving me whatever rundown you think fits the question, and/or if there's any equations that directly relate?

The following definition of observer is from A first course in general relativity by Bernard F. Schutz, page 4

It is important to realize that an 'observer' is in fact a huge information-gathering system, not simply one man with binoculars. In fact we shall remove the human element entirely from our definition, and say that an inertial observer is simply a coordinate system for spacetime, which makes an observation simply by recording the location (x, y, z) and time (t) of an event. This coordinate system must satisfy the following three properties to be called inertial:

 

(1) The distance between point P1 (coordinates x1, y1, z1) and point P2coordinates x2, y2, z2) is independant of time.

 

(2) The clocks that sit at every point ticking off the time coordinate t are all synchronized and all run at the same rate

 

(3) The geometry of the space at any constant time t is Euclidean.

 

I don't see that there needs to be an observer in quantum mechanics, just something that can make measurements. But if it is required then the above should work fine.

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For QM, just think of an observer as something that interacts with the system. If a particle hits a brick wall, the wall has "observed" the particle.

 

It's not a perfect analogy, but it's closer than the image most people bring up in their minds when they hear the word 'observer' used in quantum mechanics.

 

I think your explanation is really good. Some writers talk about this so-called quantum consciousness, as though you need a conscious observer to collapse the wave function to get a localized particle like an electron. But its really an interaction which results in the wavefunction collapse, and that, as you say, can be with a brick wall -- so human or other consciousness is not needed. At least that's my take on the subject.

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  • 1 month later...

I don't see that there needs to be an observer in quantum mechanics, just something that can make measurements. But if it is required then the above should work fine.

 

Interesting thread here! wink.gif

 

So what's a "Measurement"? tongue.gif

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Interesting thread here! wink.gif

 

So what's a "Measurement"? tongue.gif

A process that returns the value of an 'observable' quantity, a number related to energy, momentum, field intensity, etc..

It usually involves some special instrument.

Edited by Ronald Hyde
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