Undercurrent

Both observations make the wavefunction "collapse".

The error in the interpretation of Schrodinger's Cat, that MWI corrects, is the assumption that the observer is in, and stays in, a single "classical" state. The real ending of the SC experiement is, rather than the observer collapsing the cat's state, the observer entering the conjoined state of the cat. The entire cat-box-observer system gets into a state which entangles (atom decayed/cat dead/observer sees dead cat) with (atom not decayed/cat alive/observer sees live cat). The observer, reporting his findings (or even just letting the box sit open and connected to the rest of the universe) spreads this split to the rest of the world.

Before MWI, wavefunction collapse was interpreted as, "I, in my great capacity as observer, am magically making the wavefunction in the real world collapse". With MWI, it is interpreted as, "I, in my capacity as an ordinary piece of matter, am folding my wavefunction into the entangled system, with each classical state I enter preceiving only one classical state of the formerly isolated system". Thus, both the cat and the observer "collapse" the wavefunction, and the distinction between "observers" and ordinary objects is lost.

Peter Soderqvist

Soderqvist1: Because a cat is not intelligent enough to collapse the quantum wave function! Observation is only a secondary phenomenon, therefore; what matter is if the observer is aware, or not about what is going on in the quantum system, at least so says the Copenhagen Interpretation! These various interpretations are not science, because they are not falsifiable, maybe in the future! In Search For Schrodinger 's Cat is the best popular science book written about quantum mechanics! Fair use of quote from Gribbin 's home side, The Quantum Mystery Link!

John Gribbin the author of In Search for Schrodinger 's Cat!
It requires an observer intelligent enough to infer what is happening, and what would have happened if the particle had been heading towards the inner hemisphere (so a cat, for example, clearly would not be intelligent enough to cause this particular collapse of a wave function). Under these circumstances, the absence of an observation can collapse the quantum wave function as effectively as an actual observation can. At least, so says the Copenhagen interpretation. This central role for the observer -- not just any observer, but an intelligent observer -- lies at the heart of the standard Copenhagen interpretation of quantum mechanics. http://www.biols.susx.ac.uk/home/John_Gribbin/

wordsmyth

This doesn't make sense to me. Its like saying the cat cannot die because the cat isn't intelligent enough to realize that its life is potentially in danger. The cat is certainly intelligent enough to infer that it is alive and if its dead, then its intelligence is irrelevant.

Peter Soderqvist

What Gribbin is talking about is not the cat in the box!
This particular experiments has been made in the 50s, click and read the whole description! It is pointless to talk about the cat's condition in the box, because we have no means to investigate it! Science cannot say if decoherence, or wave function collapse is factual? These discussions are outside of science; it belongs to metaphysics until someone can figure out how we can test it!

Btw, Amit Goswami' s hypothesis is that the whole universe existed as a wave of possibility until a sentient self-referential being arouse, and so collapsed the wave function of the whole universe through "John Wheeler's delayed choice"
http://www.twm.co.nz/goswintro.htm

This must be the case if measurement has any validity, and for the same reason many quantum cosmologist prefer Many Worlds interpretation in order to circumvent the universal wave function description, according to David Deutsch! These hypotheses are not part of quantum theory anyway!

wordsmyth

I don't remember anything in the Schroedinger's Cat experiment that dealt with the necessity of the cat being outside the box, so if Gribbin isn't talking about the cat inside the box, then I fail to see the relevance of the cats intelligence to the Schroedinger's Cat experiment.

Quote:

This particular experiments has been made in the 50s, click and read the whole description! It is pointless to talk about the cat's condition in the box, because we have no means to investigate it! Science cannot say if decoherence, or wave function collapse is factual? These discussions are outside of science; it belongs to metaphysics until someone can figure out how we can test it!

The point is that the cat inside the box constitutes as an observer, so if the theory that an observer is required to collapse the wave function is valid, then the cat (inside the box) counts as an observer. The intelligence of the cat inside the box is not relevant to its capacity as an observer and thus has no bearing on the collapse of the wave function. The intelligence of a cat outside the box is not relevant to the experiment.

The Gribbin quote you posted directly contradicts this. Actually, the Gribbin quote appears to contradict itself, but thats just my observation.

I see no reason to believe that an observer is necessary to collapse a wave function. Therefore, I don't believe that an outside observer is necessary for the big bang to happen.


P.S. The link you provided takes me to Gribbin's Homepage. I would be more than happy to read the entire article for which you posted a small excerpt, but I would rather not have to hunt for it. Instead it would be easier if you posted a direct link to the page that is relevant to the excerpt.

Peter Soderqvist

http://www.biols.susx.ac.uk/home/Joh...um.htm#Solving

The advanced wave in the Transactional Interpretation as elaborated by Gribbin is not testable and is therefore not science either! What do you have in mind instead of consciousness as the collapser of wave function? In Copenhagen Interpretation it is a relation between the quantum system and the rest of the universe as the measuring apparatus, but what causes the collapse, when the whole universe is the quantum system, that is the point of view in quantum cosmology? :banghead:

wordsmyth

much better link. thank you. Unfortunately, Gribbin's argument still doesn't make sense because the wave function won't collapse until it strikes the outer sphere. Certainly in this situation a person is better able to infer where the collapse will happen, but the cat is still perfectly capable of observing the actual collapse. Regardless of where on the sphere the particle strikes, the cat will still be able to observe it.

I would say its not a very good argument against the cat counting as an observer in the Schroedinger's Cat experiment either.

Do you mean, if a tree falls in the forest and noone is around to hear it, does it make a sound? I suppose Gribbin would claim a cat couldn't hear it because it isn't intelligent enough to infer that it should make a sound.

Events happen all the time without the necessity of observation. If you see a tree in the forest laying on its side, do you assume that it sprang into existence that way even though you didn't see it grow from a seedling and eventually fall over? :banghead:

I admit that I am a layman when it comes to cosmology, but I don't recall reading anything that implied most cosmologists believe that the big bang was contingent on an outside observer. Sounds to me like a distinctly theistic spin in the hopes of gaining support for their belief in a creator.

We see the results of the collapse of wave functions everyday without having actually seen the collapse itself. If an observer was required, this could never happen.

Xeno

Peter - Where does intelligence come into play when something is considered "observed"? All that's required for "observation" in the Copenhagen interpretation is the precise recording of an electron's position, which can be done with either an animate (sight) or inanimate (screen) device.

ComestibleVenom

Or for that matter, a tub of hot water could count as an 'observer' since it is a large and noisy system.

ComestibleVenom

Or for that matter, a tub of hot water could count as an 'observer' since it is a large and noisy system.