Understanding 'Observe' in Physics: Definitions and Explanations

[nnope]

When I read any physics articles online I always end up receiving the wrong message. especially in terms such as 'observe'. what does this term mean when its used to describe exeperiments such as the double slit

 

[Truecrimson]

Observing here means that some information about the "observed" system is permanently recorded on an external system. The external system doesn't have to have awareness or be conscious.

It is possible that nothing is ever permanently recorded because the currently accepted fundamental law of physics is reversible (i.e. the information can be "unrecorded") but in any case it is usually argued that "natural" recording when we don't have control of the external system is practically impossible to reverse.

 

[nnope]

So can a system be continuously observed in a natural environment without the need of humans for example can an atom be observed by another atom

 

[Truecrimson]

Yes, with this meaning of observing.

 

[nnope]

Yes, with this meaning of observing.

Are you implying there are other definitions for the the term observation.

Thanks for all your help by the way :)

 

[Truecrimson]

Are you implying there are other definitions for the the term observation.

Not in standard quantum mechanics. I was just being cautious about not mixing this with the usual meaning of observing in English such as "registering it as being significant."

You are welcome!

 

[bhobba]

Observation in QM in modern times has a purely quantum definition independent of if information is recorded or not, or even can be recorded. For example it allows us to say a dust particle has an actual position independent of if any information is recorded or not. The leads to a much more common-sense view of the world where things external to us have classical properties. Its technical, but to start with simply take it as what Truecrimson said.

As your knowledge of QM develops you can come to grips with the modern view. For completeness here is THE standard text about the issue:
https://www.amazon.com/dp/3540357734/?tag=pfamazon01-20

It needs to also be mentioned there are some interpretations such as decoherernt histories that don't even have observations - in that interpretation QM is the stochastic theory of histories - without going into exactly what a history is - again its technical.

Thanks
Bill

 

[bhobba]

It is possible that nothing is ever permanently recorded because the currently accepted fundamental law of physics is reversible (i.e. the information can be "unrecorded") but in any case it is usually argued that "natural" recording when we don't have control of the external system is practically impossible to reverse.

Good point. To the OP its the resolution of the Quantum Eraser experiment you may have read about which is quite mysterious otherwise. In that case it's actually undone.

Thanks
Bill

 

[Nugatory]

When I read any physics articles online I always end up receiving the wrong message. especially in terms such as 'observe'. what does this term mean when its used to describe exeperiments such as the double slit

You'll have the same experience offline and even in respectable textbooks as well. The underlying problem is that English and other natural languages evolved to match our experience with how macroscopic objects behave. Quantum objects don't behave that way so the English words are sometimes a poor fit for quantum mechanical concepts.

The words "observation" and "particle" are the most problematic. Both are used for historical reasons, but they haven't meant what they mean outside QM since the middle of the last century.

 

[nnope]

@Nugatory this is what bothers me, every time I read a QM article I end thinking that if I turn around my computer no longer exists. the terms that are used along with the more confusing media input distorts it all. For example a while back there was an article on the news saying 'the world doesn't exist until you look at'. I mean if I'm not looking at the wall is house held up by three walls?

 

[Nugatory]

along with the more confusing media input distorts it all. For example a while back there was an article on the news saying 'the world doesn't exist until you look at'. I mean if I'm not looking at the wall is house held up by three walls?

Only one cure: don't try to learn from the pop-sci garbage, study the real thing for yourself.

 

[nnope]

Thats what i will try to do... on another thread you guys suggested some books. Hopefully ill go through them