Lost in Space

[foodchain]

I think I am confused, what and how can you define something that is a constant and or nature of QM?

 

How do you know if any property is anything that could be an intrinsic constant or nature of quantum mechanics? For instance wave particle duality seems to be the nature of anything quantum, but this is purely by measurement, meaning environment had to exist or can exist, else I would think you are saying absolutely no difference between observable and observer could exist or that a measurement could even take place, which I think then also describes then that any quantum system has constants and or a nature, like entanglement.

 

I also think to answer this question really requires a definition of time, I mean could time be described as momentum in entanglement? Why do specific geometries seem to occur but are mutable in time? Could you attribute time to being an intrinsic nature of anything quantum. I mean if time did not exist and in a quantum superposition of say everything in the universe, everything I think would happen all at once. Such as with any physical action possible via quantum mechanics such as the classical world all occurring with no time, or at once. I think if any failure could exist that would truly ruin the classical world such as tunneling to a true vacuum would have had to already occur. In less time exists as a human perception that quantum systems are naturally environments or environment as much as why the double slit experiments produced the results it did. I know this requires me to postulate something, but why would anything last and how could a measurement even exist?

[fredrik]

If I interpret you right, you note that QM deals with measurements, but in what context? You need a reference to make a measurement, and where does this measurement come from? Does "measurement form spontaneously in the void"? If so, who is measuring what? and what happens to the measurement results?

 

If this is it I think it's a really good question but not so easy to resolve.

 

This does introduce the observer into the description not only as the reference by as a part of the subject. On one hand the observer evolves, and it can make measurements which relate to himself. What we loook for is the logic of self-organisation in that sense. Why does structures start to form, and later on these structures start to "communicate / interact".

 

I think stability arises from relative inertia, even though technically everything is uncertain, intertia protects everything from happening at once. I agree this involves a deeper definition of time and is a challange.

 

Keep up the questions!

 

/Fredrik

[5614]

The thing which makes a quantum system exist in a definite state is an observer. I read a book on QM / string theory which outlined some ideas, and an interesting point made was how can the universe exist?

 

If the universe was initially some kind of big ball something, as big bang theory suggests, then this ball-thing must have been unstable (or made unstable - that's what cause the big bang). But without an external observer that ball-thing would always be in a superposition.

 

For the big bang to have occurred there must be an external observer who forced the universe out of a superposition in the first place, to make the big bang definately occur. And who is this external observer? I don't really believe in God, and neither does the author of this book (it was a purely scientific, non-religious, book), but then who broke the initial superposition that forced the universe to exist?

 

Maybe the universe has always existed. I don't know if there's a answer to the question, I don't think there is and I read the book a long time ago and don't remember what follows, although it probably just moved on, this was a minor side point. I don't even remember for sure which book it was.

 

As for wave-particle duality. We don't observe that as such, initially wave was observered, then particle. By physical theory and mathematics a new and true description of matter, wave-particle duality, was arrived at.

 

I'm not really sure if this is what you were getting at with your original post... it's some interesting thoughts though. If it's not what you meant then I appologise and can you rephrase your quesiton / idea please!?

[timo]

The thing which makes a quantum system exist in a definite state is an observer.

Assuming this was not meant in the Terry Pratchett sense of "does a falling tree make a noise if there's no one who can hear it?" (he also gives a very natural scientific answer to the question: "Who cares?") then I tend to disagree with that statement. Especially when later on you seem to say that a system "in a superposition" was not in a definite state.

 

A "superpostion of states" is just a vector in the vector-space of states (the Hilbert space) that is not a basis vector of the currently-chosen basis (degenerancy left aside, here). Barely exciting, but contradicting what I think you said: A non-basis vector is just as valid and definite as a basis vector, not some vague and undecided thing.

 

What you are probably referring to is that under the process of measurement, the current (definite!) state is projected on one of the basis vectors (or a subspace spanned by more than one, in the case of degenerancy) of the basis associated to the measured property (QM name: "Observable"). This leads to a state which will have a definite value for the observable because the mentioned basis vectors are associated to certain but possibly different values of the observable (QM terminoligy: Are eigenstates of the observable).

 

In short: While a "superposition of states" (I don't particularly like that term, but afaik above is a common usage for it) does not necessarily reflect a state with a definite value for a chosen observable, it is a clearly-defined and unique state that is just as valid as a "pure state". Might sound like nitpicking to you, but I think by not taking non-eigenstates of the current observable serious you close for yourself the doors to a more elegant way of understanding QM (via linear algebra).

 

If the universe was initially some kind of big ball something, as big bang theory suggests, ...

I'm not too familiar with modern cosmology, but I don't think "big bang theory" (whatever that shall be, I think it's just standard cosmology) suggests so. The simplemost model simply states that when approaching a certain finite value of the coordinate called time (this value being usually shifted to t=0), the distance between any two points in space approaches zero. That does certainly does not sound like a big ball to me.

 

But without an external observer that ball-thing would always be in a superposition.

What about an internal observer? I am not really sure to what extent the concept of an observer is really understood.

 

As for wave-particle duality. We don't observe that as such, initially wave was observered, then particle.

Historically? I claim that the rock-particle was known long before the rock-wave . I think your statement is true only for light, in which case you still might have to make the restriction that science started around the time of Maxwell (dunno what the view on light was before that time).

[fredrik]

For the big bang to have occurred there must be an external observer who forced the universe out of a superposition in the first place' date=' to make the big bang definately occur. And who is this external observer?

[/quote']

 

But without an external observer that ball-thing would always be in a superposition.

 

The concept of superpostion is relative to an observer as well. As to why we seem to have a superposition of complex amplitudes rather than the classical statistical mixtures is not entirely understood either IMO and it boils down to defining addition and encoding information. I think that there may be a way to understand this be considering that the observers microstructure encodes the information it's in possession of' date=' but there are various ways to encode and store information. I like to think of it like transforming the information before building it, and even his transformation may be encoded in the microstructure. This alone _could_ explain why the "statistical mixture" concept fails, but what remains is still to understand why this has evolved to be like this.

 

I don't think any string book would give you a satisfactory answer to these questions.

 

What about an internal observer? I am not really sure to what extent the concept of an observer is really understood.

 

I think this isn't understood yet either. In ordinary QM, the concept of an observer (needed for the construction) is highly idealized to the point of not beeing realistic. IMO ordinary QM foundations consider the concept of measurements in absurdum, defined without a clear connection to the microstructure of the observer, and prescription for retention of measurement results. The standard drill about infinite experiment and frequentists interpretation does not hold water except in the effective sence IMO.

 

/Fredrik

[Scyko]

Nothing could exsist without time at least not in the 3rd dimensional sence. Time is not momentum it's resistance. Matter is what happends when particles have (TIME) to settle. Without time nothing physical could be, even the threads of energy that make up particles vibrate at the speed of light which is also a measurement of time:D Big Bang is still a theory, for all we know it never happened outside of our own galaxy:doh: Also not sure if I understand the concept as being an observer, but I can perceive quite a bit.

[foodchain]

If I interpret you right, you note that QM deals with measurements, but in what context? You need a reference to make a measurement, and where does this measurement come from? Does "measurement form spontaneously in the void"? If so, who is measuring what? and what happens to the measurement results?

 

If this is it I think it's a really good question but not so easy to resolve.

 

This does introduce the observer into the description not only as the reference by as a part of the subject. On one hand the observer evolves, and it can make measurements which relate to himself. What we loook for is the logic of self-organisation in that sense. Why does structures start to form, and later on these structures start to "communicate / interact".

 

I think stability arises from relative inertia, even though technically everything is uncertain, intertia protects everything from happening at once. I agree this involves a deeper definition of time and is a challange.

 

Keep up the questions!

 

/Fredrik

 

Well, to me QM is hard to define. It has its physical basis in experiment for instance, and then of course the math that can model it. I truly think that QM is far more natural in a classical sense as in having a nature, with that said I just think the variance involved in QM, such as probability alone, makes understanding this 100% close to zero currently.

 

This is an idea I have about QM for instance, I would just like to know how to make it falsifiable. I don’t know enough about QM really in any sense to do it for myself. I think giving some postulates, one of probability and or one of entanglement, what bounds could you place on that as a nature? Being we can observe these effects in our classical world what does that mean for any other experience such as being able to see? Its really just an idea about trying to reduce any classical phenomena to a quantum one or ones, or possible ones. The one I would really like to test is conservation of energy. If energy cannot be created or destroyed, only change forms, then how does it go about this. Could QM always have to obey this law? To what extent, such as just entanglement?

 

So how do you test well enough at a QM level to know that conservation of energy is an absolute for anything quantum? Even if you could prove it now, how do you know that it was not by some previous domain of QM that the probability to conserve energy even came about or evolved. What really is the bounds or nature of QM and how can we know or test such truly?

[5614]

What you are probably referring to is that under the process of measurement, the current (definite!) state is projected on one of the basis vectors (or a subspace spanned by more than one, in the case of degenerancy) of the basis associated to the measured property (QM name: "Observable").

 

In short: While a "superposition of states" (I don't particularly like that term, but afaik above is a common usage for it) does not necessarily reflect a state with a definite value for a chosen observable, it is a clearly-defined and unique state that is just as valid as a "pure state". Might sound like nitpicking to you, but I think by not taking non-eigenstates of the current observable serious you close for yourself the doors to a more elegant way of understanding QM (via linear algebra).

Indeed that is what I meant by "definite state". I don't think it's nitpicking, my understanding is simple to the point where it can sometimes be technically incorrect. You make a very good point.

 

 

Especially when later on you seem to say that a system "in a superposition" was not in a definite state.

By that all I meant was that you cannot assign, for example, a "up" or "down" value to that system. It is in a superposition of both. I meant it did not have a "definite value for a chosen observable".

 

 

I'm not too familiar with modern cosmology, but I don't think "big bang theory" (whatever that shall be, I think it's just standard cosmology) suggests so. The simplemost model simply states that when approaching a certain finite value of the coordinate called time (this value being usually shifted to t=0), the distance between any two points in space approaches zero. That does certainly does not sound like a big ball to me.

Appologies, this is a case of sloppy wording on my part. I was basically getting at the idea of whatever the pre-big-bang universe was being some (unknown) "thing", that then expands. However I had a mental picture of a ball/balloon being blown up, so I (stupidly) described the pre-big-bang "thing" as a "ball-thing", which is wrong. I even used the term "big" merely to imply that everything we now know was all contained in the small early universe. I haven't been on these forums recently, I blame that for my poor choice of words! The big bang does not say what happens, other than that the radius of the universe tended to 0.

 

 

What about an internal observer? I am not really sure to what extent the concept of an observer is really understood.

It was just a thought path I found an interesting one, not something I have dwelled on for long. But, after the universe expanded beyond the Planck length AFAIK the first thing to be was the quark "soup". I have no idea if that could count as an observer. I do agree that the concept of an observer is not understood, especially when we probe its meaning like this.