What does the act of observing do exactly?

  • I
  • Thread starter benorin
  • Start date
  • #1
benorin
Homework Helper
Insights Author
1,395
148
My question is simple though I fear the answer may be complex: What does the act of observing do exactly? I hear observing does some unexpected things in quantum (I wouldn't doubt there is a religon based on it).

I am a math major with a love of physics though I'm not that versed in it so please do pile on the formulas if you wish but be nice with the physics. Thanks for responding in advance,

-Ben Orin
 

Answers and Replies

  • #2
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
It may range from checking whether a silver spot is on the left or right to a click in a photodetector to recording a number in the memory of a computer. It even may mean doing months of calculations and checks based on collision experiments to measure the mass of the Higgs particle.

That the act of observing does something to the observed system is of the same kind as that observing timid game. However, microscopic events are sometimes so timid that one usually (i.e., except in nondemolition experiments) cannot avoid at all affecting the observed with the observation.

The claims of the Copenhagen interpretation that an observation forces the state vector to collapse to an eigenstate of the operator observed corrsponding to the eigenvalue measured is an approximate idealized description of the measurement process, appropriate in simple cases (only).

The claim ignores that observations take time, that measurement results ae often inaccurate, and that many real measurements are not related to an operator but rather to a POVM. It also ignores that observation is done in the frame of an observer, and that different observers may therefore - in the same situation - measure different things. Finally, it completely abstracts from what it means to make a measurement/observation.

As a mathematician you'll probably like my online book on quantum mechanics.
 
  • Like
Likes dlgoff, QuantumQuest and bhobba
  • #3
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
(I wouldn't doubt there is a religon based on it).
You'll see that interpretations of quantum mechanics are like religion - fiercely debated, without the possibility to reach agreement. The agnostic part is called shut-up-and-calculate, but it leaves unanswered all important questions of how the math relates to reality - or answered ad hoc on a subjective case-by-case basis in terms of pieces of unreflected material from one or more of the established religions.
 
Last edited:
  • #4
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
Thanks for responding in advance,
It should read: ''Thanks in advance for responding'' - unless you think we have time machines.
 
  • Like
Likes Demystifier and AlexCaledin
  • #5
908
223
It should read: ''Thanks in advance for responding'' - unless you think we have time machines.


:-)


Relativistic??
 
  • #6
361
578
My question is simple though I fear the answer may be complex: What does the act of observing do exactly?

From my reading of W. Heisenberg and H. Stapp (who subscribes to Whitehead's view) I got the simplest answer: the act of observing does physical reality - that is, the physical reality consists of observation acts (events); but events are connected by the underworld ("realm") of potentiality which is what QM calculates.
 
  • #7
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
the physical reality consists of observation acts (events); but events are connected by the underworld ("realm") of potentiality
And what about the reality before there were observers? Did our universe emerge from the preexisting underworld the moment when the first human (or the first amoeba?) observed something?
 
  • #8
361
578
Well, yes, when the observation process started, the universe emerged;
how exactly it started is not a scientific question...
 
  • #9
908
223
People generally act different when they know they are observed.
 
  • Like
Likes Demystifier and 1oldman2
  • #10
908
223
Well, yes, when the observation process started, the universe emerged;
how exactly it started is not a scientific question...

Huh???
 
  • #12
45
1
Most deep questions are not scientific. One cannot build anything from just fundamental particles as most classical processes emerge and are not resultant of properties of fundamental particles. Embrace emergence, it's already established as science.
 
  • #13
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
most classical processes emerge and are not resultant of properties of fundamental particles.
All classical processes emerge as good approximations of the interplay of fundamental quantum fields.

Nothing can emerge unless it results from more fundamental processes.
 
  • #14
45
1
Fundamental processes is not the same as fundamental particles in your usage, right? Because if not, pretty much nothing that we observe can be derived from the properties of electrons and quarks. I digressed but i got the idea that some participants in this thread are of the opinion that science has closed most chapters. No, we can only describe what we observe and at this point it's almost as if the fundamental mechanics of reality are invisible.
 
  • #16
A. Neumaier
Science Advisor
Insights Author
8,059
3,955
Fundamental processes is not the same as fundamental particles in your usage, right?
For each level that is not fundamental there is a more fundamental level below from which that level emerges as a n effective theory.

Of course it will always be unknown whether what we regard as fundamental is not also only a level with more below. But I wouldn't be surprised if with quantum gravity plus the standard model we already reached the bottom.
 
  • #17
45
1
Yes. And taken at both ends, we can never deduce what we observe from the lowest level of fundamental particles. Just looking at electrons and quarks you'd never deem possible the emergence of vision, metabolism, hunger, appetite, bacteria, rain, computers, grannies, etc
 
  • #18
908
223
But all those phenomena can only be explained coherently because of knowledge of quarks

That's why science is the best explaining g tool humans have invented, nothing g Is better or even close.
 
  • #19
45
1
Quite the opposite - 'knowing of quarks' explains nothing of the observed behaviours i referenced above. QM would be the worst example one can find for describing observed reality in ALL fields of science. Period.
 
  • #20
908
223
I disagree, we can explain chemical bonds by QM, that = everything.
 
  • #21
10,060
3,161
Quite the opposite - 'knowing of quarks' explains nothing of the observed behaviours i referenced above.

It proceeds by each layer explaining the one above. The standard model explains atoms which explains chemistry etc etc. Why anyone would think otherwise has me beat.

Thanks
Bill
 
  • #22
381
118
Nothing can emerge unless it results from more fundamental processes.

tautological: that's the definition of emergence

I wouldn't be surprised if with quantum gravity plus the standard model we already reached the bottom.

I would. I'll wager 1000 bragging points that in 2 decades you'll see I was right. But since I won't be around to collect my winnings, at that time you'll have to take 1000 anti-bragging points yourself ... are we on?

Just looking at electrons and quarks you'd never deem possible the emergence of vision, metabolism, hunger, appetite, bacteria, rain, computers, grannies, etc

very true

QM would be the worst example one can find for describing observed reality in ALL fields of science.

now you're overdoing it

The standard model explains atoms which explains chemistry etc etc. Why anyone would think otherwise has me beat.

Their reasons can be summed up by the phenomenon called emergence - I suppose
 
  • #23
908
223
so emergence is just a catch all label for splaining everything from the bottom up except with none of the splaining ie, just the label that sits on top.

amiright?
 
  • #24
10,060
3,161
so emergence is just a catch all label for splaining everything from the bottom up except with none of the splaining ie, just the label that sits on top.

I don't quite understand your point.

But as practical matter its done that way. Of course in principle you could use the standard model to directly explain say biochemistry but you would have rocks in your head to try that.

Gell Mann has an interesting take:
https://www.ted.com/talks/murray_gell_mann_on_beauty_and_truth_in_physics?language=en

Thanks
Bill
 
Last edited:
  • #25
47
8
Dear benorin,

The mathematical formalism adopted by Werner Heisenberg leaves clear that in the instant the observation of one particle is made, all probabilities disappear. Strangely, since the formulation made to this day, numerous discussions about the significance of this disappearance occur, maintaining that there is something misterious in it (Copenhagen interpretation). Nevertheless, when we have a dice in hand before we throw it the possibility of each face falling upside is one to six. In the moment it falls upon the table and immobilize, to us it's clear one can no more speak of probabilities, as one of the faces was defined. Its obvious, there is nothing misterious in it, as even Einstein and Niels Bohr concurred. A supposed “observator's influence” is therefore nonsense.
 
  • Like
Likes benorin and marcophys
  • #26
43
18
I find the question in this thread extremely justified. In all humility I for myself have arranged myself starting from the point of view that physics does not deal with reality but with models that allow to predict an observed behaviour. So for myself I do live with the fact for me, that reality has not been perceived by us, but that the physics of creating models that allow to predict correctly and even discover where they do no fit is helping us to improve our models. The experiment with the photon and the 2 slits for me is a valid prove that we have not yet approached what reality is and even the notion of reality could be questioned.
I think humanity has find out how much we have to still research when you consider what a small amount of the universe we have been able to perceive at all. Black energy and black matter being the topic.
Reflecting about our universe in the context of the 6 numbers so crucial for the universe being as it is, according to our physical models, and adding to this the concept of a multiverse as sheets next to each other, why not trying to identify how parameters would have to be to achieve a goal, like getting from one place to another without the limitation of the speed of light! Why not trying to find more parameters of our universe that having a certain value would make the above achievable for a civilization as ours. Basically not only looking for parameters that explain what we observe, but also parameters that make objectives feasible! Why could it not be that we happen to be that sheet in a multiverse where those parameters apply?
 
  • #27
I greatly enjoyed "Quantum: Einstein, Bohr and the Great Debate about the Nature of Reality" by Manjit Kumar. Two of the greatest minds of the 20th century couldn't agree on an answer to your question. But the book (and it's not the only one) is more about philosophy with a great deal of fascinating history. I haven't studied any of this in many years, but for what it's worth I had problems with both viewpoints. There's something extremely weird (to us macroscopic beings) going on at that size.
 
  • #28
1,799
775
I greatly enjoyed "Quantum: Einstein, Bohr and the Great Debate about the Nature of Reality" by Manjit Kumar..

I have a copy of that, and yes I also enjoyed it also.

Another book you may not have come across is 'The Quantum Story' by Jim Baggott. I also enjoyed that.
 
  • #29
631
132
I disagree, we can explain chemical bonds by QM, that = everything.
Can QM predict the density of water?
 
  • #30
stevendaryl
Staff Emeritus
Science Advisor
Insights Author
8,942
2,931
Can QM predict the density of water?

There are a number of parameters that we don't know how to determine, from first principles:
  1. The charge of the electron.
  2. The mass of the electron.
  3. The mass of a hydrogen nucleus.
  4. The mass of an oxygen nucleus.
But I think that quantum mechanics can in principle determine all the other properties of water from these parameters. In practice, I'm not sure how much is actually doable.
 

Related Threads on What does the act of observing do exactly?

Replies
3
Views
1K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
4
Views
2K
Replies
5
Views
1K
Replies
78
Views
6K
Replies
8
Views
7K
Replies
4
Views
2K
  • Last Post
3
Replies
76
Views
10K
Top