Does Observation Create Reality in Quantum Physics?

[question99]

According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated? For example, if the moon doesn't exist when it is not looked at, then why does the moon keep appearing when we do look at it. Is "reality" like a video game where programmed scenery is generated as the player moves around?

 

[mfb]

According to quantum physics, things don't exist until being observed/measured.

It depends on the interpretation of quantum physics. There are many of them, with different descriptions what "reality" is. For predicting measurements, it does not matter, they all agree (they have to, because otherwise experiments would rule them out).

For example, if the moon doesn't exist when it is not looked at

That is wrong in all interpretations.

 

[phinds]

This is a mis-interpretation of QM. The moon is there whether you are looking at it or not. The Copenhagen Interpretation is sometimes taken as saying that things observed do not exist, but it is my understanding that it doesn't say that and in any case, ALL interpretations of QM reduce in reality to "shut up and compute" in which things exist.

Now there are things at the quantum level, such as the position of an electron, that have no value until they are measured but that is not at all the same as saying there is no electron.

EDIT: I see mfb beat me to it

 

[nikkkom]

According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated?

Because measurements don't give completely random results. Observations of the Moon are strongly likely to detect the same Moon, not a giant cheese donut. For most macroscopic cases, chances of observing something "unusual" due to quantum nature of physics are unimaginably tiny.

 

[bhobba]

According to quantum physics, things don't exist until being observed/measured.

Thats not what Quantum Physics says - its silent on things existing until observed or measured. We have interpretations where such is the case ie it exists at all times regardless and ones where it doesn't. Pick the one that suits you - its your choice.

Thanks
Bill

 

[bhobba]

That is wrong in all interpretations.

Just to expand on that point. All interpretations have the same quantum formalism and that formalism has something called decoherence. The moon at all times is constantly observed by the environment and in fact that's what gives it its classical properties of a definite position and momentum at all times - at least way way below our ability to detect quantum effects. Its not just the moon BTW - its everything around us and why we don't observe quantum effects in everyday life. Remove that interaction and some very strange things occur:
http://physicsworld.com/cws/article/news/2010/mar/18/quantum-effect-spotted-in-a-visible-object

To the OP you probably got that from something Einstein said. He had his issues with QM - he eventually conceded it was correct (that happened after a famous exchange with Bohr that required his equivalence principle to resolve - he tipped his hat to Bohr - literally - and never questioned its validity from that point on) but believed it was incomplete. That is not to say he didn't understand QM - he understood it very well - always keeping a copy of Dirac's famous text with him saying I will need to consult my Dirac. What the issue is, QM has moved on a lot since those times and so has our understanding. It actually turns out the joke was on Bohr and Einstein - they were both wrong:
http://www.fisica.ufmg.br/~dsoares/cosmos/10/weinberg-einsteinsmistakes.pdf

Thanks
Bill

 

[atyy]

For example, if the moon doesn't exist when it is not looked at

That is wrong in all interpretations.

Thats not what Quantum Physics says - its silent on things existing until observed or measured. We have interpretations where such is the case ie it exists at all times regardless and ones where it doesn't. Pick the one that suits you - its your choice.

So do bhobba and mfb disagree here? If it is wrong in all interpretations, then it is not true that quantum physics is silent on such things.

 

[bhobba]

So do bhobba and mfb disagree here? If it is wrong in all interpretations, then it is not true that quantum physics is silent on such things.

Of course we don't disagree. From the QM formalism alone objects like the moon are there if no one is looking because its being observed all the time by the environment. That's the exact point Weinberg was making as to why both Einstein and Bohr were wrong.

And to forestall a thread that goes nowhere and confuses the OP, its exactly as Weinberg says, considerable progress has been made, but some issues remain, although they are not what Bohr and Einstein thought. That is a legit thread in itself but should not be sidetracked in this thread.

To the OP - its basically a clarification on what an observation is.

Thanks
Bill

 

[Bruno81]

According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated? For example, if the moon doesn't exist when it is not looked at, then why does the moon keep appearing when we do look at it. Is "reality" like a video game where programmed scenery is generated as the player moves around?

When in doubt, stick to known facts, if available. I find the following video very illuminating esp. the end where prof. Brian Cox discusses the non-Newtonian universe and his conclusion at the very end(note the GR slant, it's still relevant to your questions albeit from a different and more 'visible' angle).

https://m.youtube.com/results?q=brian cox feather ball&sm=3

Lots of people find it difficult to deal with a potentially unknowable post Newtonian reality.

 

[nikkkom]

Of course we don't disagree. From the QM formalism alone objects like the moon are there if no one is looking because its being observed all the time by the environment.

This changes nothing. (The Moon + the environment) is still a physical quantum system which you, a human, then observe. It still exhibits quantum effects.

This means that "the environment" is in superposition of seeing the Moon in all possible states, even some unexpected states ("a giant cheese donut"), with all strange state having unimaginably tiny superposition coefficients.

And then you, the observer, "collapse" (The Moon + the environment) into one of these states. Most probable states are where "the environment" sees the Moon as a rocky ball with all familiar craters where they should be.

 

[bhobba]

This changes nothing. (The Moon + the environment) is still a physical quantum system which you, a human, then observe. It still exhibits quantum effects

It does. But this is not the thread to discuss it. It is now well understood that observations can be defined using nothing but QM. Start a new one if you want to pursue it.

It has been discussed many times in many meandering threads. Derailing this one will not really serve any purpose.

Thanks
Bill

 

[atyy]

Of course we don't disagree. From the QM formalism alone objects like the moon are there if no one is looking because its being observed all the time by the environment. That's the exact point Weinberg was making as to why both Einstein and Bohr were wrong.

And to forestall a thread that goes nowhere and confuses the OP, its exactly as Weinberg says, considerable progress has been made, but some issues remain, although they are not what Bohr and Einstein thought. That is a legit thread in itself but should not be sidetracked in this thread.

That is not correct because the issues that remain are not minor. Decoherence at best causes apparent collapse.

 

[Demystifier]

Actually, there are interpretations which say that the Moon does not exist when it is not observed. This is the most explicit in the solipsistic HV interpretation
http://lanl.arxiv.org/abs/1112.2034 [Int. J. Quantum Inf. 10 (2012) 1241016]
but also implicit in many interpretations that insist that nature is completely local and that neither local nor non-local HV's of the Bell type do not exist.

 

[bhobba]

That is not correct because the issues that remain are not minor. Decoherence at best causes apparent collapse.

Its got nothing to do with interpretations, apparent collapse, or anything of that ilk. Its simply a fully quantum definition of what an observation is.

It interpretatively resolves nothing. All it does is say an observation occurred by the interaction on the moon by the environment - hence its being observed all the time.

If you don't want to accept that definition you are free to do so - but if you do you need to define it in some other way. Copenhagen was rather lax in doing that - hence Wienberg's comment.

Thanks
Bill

 

[bhobba]

Actually, there are interpretations which say that the Moon does not exist when it is not observed.

That's not the point. The point is its interacting with the environment, gets entangled with it, and that's is the modern view of what an observation is.

Thanks
Bill.

 

[Hornbein]

According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated? For example, if the moon doesn't exist when it is not looked at, then why does the moon keep appearing when we do look at it. Is "reality" like a video game where programmed scenery is generated as the player moves around?

Werner Heisenberg said in a private letter that the moon didn't exist until we look at it, but I think he was exaggerating.

My personal interpretation that very simple things exist in an undefined state until they whack into something that is more complicated than they are. The Moon is very complicated. The Moon has more states than do we, so it would be more correct to say that we exist in an undefined state until the Moon observes us. As this interpretation is unflattering to the ego of Humankind, it is unlikely to garner a large following.

I have no patience with including "conscious" in all this. There is nothing in the math that has anything to do with consciousness.

 

[Heinera]

Is "reality" like a video game where programmed scenery is generated as the player moves around?

Well, that could be a perfectly consistent interpretation of quantum mechanics, which would mostly take the "mystery" out of it (except for "heck, what kind of computer is this implemented on?") And since pondering over interpretations can ultimately lead one to your suggestion, I have to confess that my favorite interpretation is "shut up and calculate"

 

[bhobba]

Werner Heisenberg said in a private letter that the moon didn't exist until we look at it, but I think he was exaggerating.

Things have moved on a lot since Heisenberg's time.

You are taking a very weird view of things if you believe looking at the moon affects anything. This whole business is from the weakness in Copenhagen - its lax in defining what an observation is:
http://motls.blogspot.com.au/2011/05/copenhagen-interpretation-of-quantum.html

That is rectified in modern times by fully quantum theories of what an observation is - although various interpretations have differing takes on it. For example in Consistent Histories its a theory about histories, Quantum Darwinism it comes from the emergence of stable pointer states. Its really not germane exactly how its done - the point is we now have fully quantum theories of observation. The moon is always there because its being observed constantly by the environment.

Thanks
Bill

 

[Bruno81]

Is is established that there exists a classical environment made of solid ball-like atoms that can decohere quantum systems in their motion?

 

[bhobba]

Is is established that there exists a classical environment made of solid ball-like atoms that can decohere quantum systems in their motion?

Everything is quantum - nothing is fundamentally classical. The classical world emerges from the quantum.

Thanks
Bill

 

[atyy]

Its got nothing to do with interpretations, apparent collapse, or anything of that ilk. Its simply a fully quantum definition of what an observation is.

It interpretatively resolves nothing. All it does is say an observation occurred by the interaction on the moon by the environment - hence its being observed all the time.

If you don't want to accept that definition you are free to do so - but if you do you need to define it in some other way. Copenhagen was rather lax in doing that - hence Wienberg's comment.

But if you define an observation in this way, then what does an observation have to do with reality, the subject of the OP?

In this way, the environment is just some part of the wave function or state vector. But we don't know if the quantum state is real or just a tool to calculate the probabilities of measurement outcomes, so the observation of a part of the wave function by another part of the wave function doesn't address the notion of reality.

 

[bhobba]

But if you define an observation in this way, then what does an observation have to do with reality, the subject of the OP?
.

Its an assumption of QM observations are very real. Being careful what one is doesn't change that.

Before going any further, if you have issues with this, you need to define what an observation is, and it needs to be non circular. In particular it can't use classical concepts because that will mean you can't use it to explain the classical world since you assume it from the start. That of course doesn't invalidate it, but is a blemish, a blemish in modern times considerable effort has been made to address. This was the point both Lubos and Weinberg made.

There is nothing mysterious about any of this. Its simply fixing an issue the early founders of QM didn't bother with - again as explained by Lubos.

Simply pick any axioms of QM eg:
http://math.univ-lyon1.fr/~attal/Mescours/QM.pdf

There are others - some more elegant, others more intuitive - its not really critical. The critical point is they do not carefully define an observation. All this does is give a careful QM definition. It means things like the CBMR can be an 'observer'. Because its everywhere then things are being observed all the time. That's why in modern times the OP's question is no loner relevant - the moon is being observed all the time.

Added Later:
Consider a Geiger counter. There is little doubt when it clicks that is an observation. Consider a dust particle that interacts with the CBMR. It is well known this to leads to a dust particle with a definite position. Why would you count the Geiger counter as an observation and not the CBMR? That's the crux.

Thanks
Bill

 

[martinbn]

Here is my opinion about the moon. The quote is "The moon isn't there if no one observes it." and the emphasis is not on is, but on there. The moon exists (whatever that may mean), but its position i.e. the coordinates have no value until they are measure. So the moon is, but it is meaningless to say that it is there unless you measure the coordinates.

 

[Bruno81]

In other words, without knowing what an observation is, has anything been resolved or advanced since the time of Heisenberg?

 

[bhobba]

So the moon is, but it is meaningless to say that it is there unless you measure the coordinates.

That's the point of the modern view. It can be shown that for objects like the moon interaction with the environment is what gives it a position ie acts as a position measurement (it's to do with the radial nature of such interactions).

Don't get confused by sophistry such as is the click of a Geiger counter an observation if no one hears it. That's the stuff philosophers argue about - in physics things are much more common sense - of course it clicks if no one hears it.

Thanks
Bill

 

[bhobba]

In other words, without knowing what an observation is, has anything been resolved or advanced since the time of Heisenberg?

There have been advances in many areas - not just clarifying what an observation is eg Bells theroem, Gleasons theroem.

IMHO one of the biggest advances has been clarifying exactly what the formalism of QM is about:
http://arxiv.org/pdf/quant-ph/0101012.pdf

Thanks
Bill

 

[Bruno81]

There have been advances in many areas - not just clarifying what an observation is eg Bells theroem, Gleasons theroem.

Thanks
Bill

But other areas are outside the scope of this thread. Has anything been achieved wrt to understanding what an observation is since Heisenberg? Please no philosophy.

 

[bhobba]

But other areas are outside the scope of this thread. Has anything been achieved wrt to understanding what an observation is since Heisenberg?

Of course.

That's what my replies have been about.

I will be specific. We now know a lot more about decoherence and these days the definition of an observation is once decherence has occurred. That means pretty much any kind of entanglement is an observation. Objects all around us are entangled with its environment all the time - that's why they are there when no one is looking - because its not conscious beings that look at objects - its the entire environment.

I will not hide that there are issues - you can do a search on the factorisation problem for example and find long threads - but they are generally considered technicalities.

If you want more details the following gives it at a reasonable level:
http://press.princeton.edu/titles/6662.html

Thanks
Bill

 

[DrClaude]

The OP's question has been answered. Time to lock this thread.