The Sneaky Universe

[Cyphermage]

We're all familiar with the conventional interpretation of quantum mechanics, whereby the Universe evolves via unitary evolution of its wavefunction, interspersed with reduction in which the act of observation collapses the wavefunction into an eigenstate of a particular observable.

There are all sorts of cute quantum oddities we can demonstrate, like the quantum eraser effect, in which a later choice to destroy or observe a measurement affects whether interference occurs earlier in the apparatus.

What, then, does quantum mechanics say about disparate multiple observers. Do two observers who never meet and exchange information have to see the same thing when they perform a measurement on a system? Do we all have a private universe, which agrees with the private universe of another only where intersections occur?

Is there an objective reality that applies to all of us, and is it even possible to devise an experiment which could detect if this is not the case?

 

[tsg]

We're all familiar with the conventional interpretation of quantum mechanics, whereby the Universe evolves via unitary evolution of its wavefunction, interspersed with reduction in which the act of observation collapses the wavefunction into an eigenstate of a particular observable.

Yeah, uh, I was just thinking that.

I have nothing to add, I just like being a wiseass.

 

[l0rca]

Ultimately very doubtful, if you consider that quantum mechanics is a theory of prediction, and not philosophy. It also conflicts with general relativity, which means one or both are right.

There are all sorts of cute quantum oddities we can demonstrate, like the quantum eraser effect, in which a later choice to destroy or observe a measurement affects whether interference occurs earlier in the apparatus.

Quantum mechanics is the ultimate induction science, since our observations at the quantum level are almost always outside our assumptions. I'm confident though, the in the future, we'll think of something, or find something that can describe the empiric in a satisfiable way. *coughM-Theorycough*

What, then, does quantum mechanics say about disparate multiple observers. Do two observers who never meet and exchange information have to see the same thing when they perform a measurement on a system? Do we all have a private universe, which agrees with the private universe of another only where intersections occur?

General Relativity says something about this too. It depends where the light arrives first. Two actions simultaneously occuring may appear to happen sequentially, but in opposite sequence, to observers at different angles. Light from one object's light may meet an observer before the other object's light does.

But so far as your musings, of private universes etc., I don't see any good reason to arrive at that idea.

 

[Cyphermage]

But so far as your musings, of private universes etc., I don't see any good reason to arrive at that idea.

Could you suggest an experiment to verify the existence of a single objective reality that is the common experience of all observers?

 

[l0rca]

Could you suggest an experiment to verify the existence of a single objective reality that is the common experience of all observers?

Obviously not. But that retort to my comment is similar to asking me to prove the existence of god as a rhetorical question to spark my interest in It's possible existance.

 

[Apathia]

I don't think there's anything sneaky about it, as if there were some implicate order thingy hiding its absolute objective realith from the general public.
It may not be to everyone's taste, but I don't mind the community process of our reality.

Two desparate observers meet and we get a "collapse." Or a collusion.

I guess if must have an absolute objectivity instead of a functional one, we can evoke the every popular parrallel universes, split hairs, now called strings, or find reality very much a onion with layer under layer of branes.

Branes! it's enough to make one a science zombie!

 

[RandFan]

It [quantum mechanics] also conflicts with general relativity, which means one or both are right.

A & B are in conflict therefore A is true or B is true or A&b are true.

You are going to have to help me out with this one.

 

[l0rca]

A & B are in conflict therefore A is true or B is true or A&b are true.

You are going to have to help me out with this one.

*slaps forehead*

Oops. I meant wrong. They're wrong, wrong!

 

[RandFan]

*slaps forehead*

Oops. I meant wrong. They're wrong, wrong!

Thanks. I thought science was looking for a unifying theory?

 

[l0rca]

Thanks. I thought science was looking for a unifying theory?

Yes; I hope I didn't say anything that would hint the contrary.

But for right now the calculations the contender provides (M-Theory, among others which are in even earlier embryonic states) are too complicated and still changing to offer anything worthwhile so far as scientific prediction go. General Relativity and Quantum Mechanics/Standard Model may contradict each other, and provide no good answers where they intersect (black holes, big bangs, etc), but they've so far offered the best predictions for their parts as physical theories.

Also, so I don't leave it out: although it is not reaching for a title such as Theory of Everything, the Loop Quantum Gravity theory attempts to mesh General Relativity and the Standard Model:

http://www.everything2.com/index.pl?node_id=1485155
http://en.wikipedia.org/wiki/Quantum_loop_gravity

 

[RandFan]

Yes; I hope I didn't say anything that would hint the contrary.

But for right now the calculations the contender provides (M-Theory, among others which are in even earlier embryonic states) are too complicated and still changing to offer anything worthwhile so far as scientific prediction go. General Relativity and Quantum Mechanics/Standard Model may contradict each other, and provide no good answers where they intersect (black holes, big bangs, etc), but they've so far offered the best predictions for their parts as physical theories.

Also, so I don't leave it out: although it is not reaching for a title such as Theory of Everything, the Loop Quantum Gravity theory attempts to mesh General Relativity and the Standard Model:

http://www.everything2.com/index.pl?node_id=1485155
http://en.wikipedia.org/wiki/Quantum_loop_gravity

Thanks Mercury.

 

[Yahzi]

What, then, does quantum mechanics say about disparate multiple observers.

Once the wave form is collapsed, it is collapsed. Therefore all subsequent observations are identical.

Is there an objective reality that applies to all of us,

Yes.

and is it even possible to devise an experiment which could detect if this is not the case?

By definition... no.

If you are trapped in your own private universe, how are you ever going to tell me you are trapped in your own private universe? If we can't exchange information, how can we exchange the information that we observed things differently?

 

[Cyphermage]

If you are trapped in your own private universe, how are you ever going to tell me you are trapped in your own private universe? If we can't exchange information, how can we exchange the information that we observed things differently?

Consider the following experiment. A pair of entangled photons with identical but undetermined spin separates and after a while, one arrives at a distant laboratory, where it is observed at about the same time I observe the other one. If I compare notes with the distant laboratory, I will see that their observation as to whether their photon is spin-up or spin-down matches mine.

Considering the locale of my observation as one system, and the locale of the distant laboratory as another system, the question I pose is as follows. If the two systems have no possibility of ever interacting at all at any time in the future, and each is forever lost to the other, are their observations still required to match.

Consider, for instance, that the laboratory crosses the event horizon of a black hole just as they peek at their photon. We know that the interpretation that the photon is in a definite spin state prior to being observed, and we just don't know what it is, is incorrect, since we can devise experiments to show that QM is incompatible with such "hidden variable" theories.

So each observer has a photon with a wavefunction that is a superposition of spin-up and spin-down, with no causal connection between them at any time in the future. Could the wavefunctions then collapse independently of eachother, since no possibility exists that we will observe the inconsistancy.

Do any experiments exist where the choice to forever uncouple the two branch systems is made on the fly, producing observations over many repetitions which statistically suggest which of these two scenarios is taking place.