[eddysciencefan (OP)]

hello guys, first time posting so if my question seems obvious or silly please forgive me, and if i'm incorrect in any way feel free to correct me.

quantum theory allows for fundamental particles to be in 2 places at once as long as we don't know the exact position. so imagine if we had a oxygen atom, 2 protons and one electron locked in a covered container. surely the electron would be able to combine with both protons at once to produce 2 hydrogen atoms, which in turn would be able to combine and produce a water molecule.

would the energy in the water molecule become greater than it originally started (as this is against the laws of thermodynamics as far as i'm aware) or would it be water whilst unobserved and return to its original state as separate protons and electron when we look at it again?

[dlorde]

This sounds like a variation of the Schrodinger's Cat thought experiment. As I understand it, the many-places-at-once superposition of a particle is resolved (in some fashion) when it interacts with another particle in any way; in descriptions of QM this is often called a 'measurement', referring to an interaction that enables some observer to detect the event. The observer isn't necessary - any particle interaction will have the same effect. This means that your electron would no longer be in superposition once it made the first proton interaction, so there would be no second proton interaction.

It's actually a bit more complicated than that, in the sense that until we do make some measurement or observation of the system in the box, we don't know which proton, if any, the electron has combined with; so, for us, the whole enclosed system is in a state of superposition (one, the other, and neither of the interactions have all occurred) until we poke our noses in to see - at which point we find ourselves looking at a definite result. The precise interpretation of what actually happens at this point is debatable. One interpretation is that all outcomes actually happen, each in a separate 'universe', and each outcome is observed by separate versions of us in each universe... however, both interactions can't happen in the same universe, because there is only one electron, so thermodynamics is safe in that respect.

[flr]

One interpretation is that all outcomes actually happen, each in a separate 'universe', and each outcome is observed by separate versions of us in each universe...

 This interpretation with multiple universes is complete garbage in my opinion, and show how wrong one can get it if is over-interprets some math in complete disregard with reality.

[dlorde]

It seems that only the maths satisfactorily describes what happens in reality. I haven't yet heard an interpretation that sounds reasonable and doesn't lead to contradictions. 'Many worlds' seems to be more consistent with the maths than others, but is correspondingly harder to accept.

You pays yer money and you takes yer choice. Opinion among physicists seems divided; the pragmatic approach is to "shut up and calculate".

 

[eddysciencefan (OP)]

thanks guys, clears it up slightly but i'd still like to know if there ever was a water molecule in the box and if it would be stable or if it would break down.

i've certainly come across the "shut up and calculate" attitude before. and understand that is where theory pulls in a very strong direction. but i feel unless it can be understood and visualized then a proper understanding isn't possible.

say for instance there was a current running through the box and it could only make a full circuit when the water molecule is complete, what results would that show, would we have had a full circuit?

[evan_au]

At some points in time you could certainly end up with a H₂⁺ ion or a H₂0⁺ ion. However, these ions may be neutralised if they got too close to the walls of the box, and grabbed an electron from the box wall.

You would not have 2 hydrogen atoms at the same instant in time, or a neutral H₂ molecule as there is only 1 electron and 2 protons. Whenever you looked, the electron would be in one place or the other.

[lightarrow]

quantum theory allows for fundamental particles to be in 2 places at once as long as we don't know the exact position. so imagine if we had a oxygen atom, 2 protons and one electron

? You intended 2 hydrogen atoms bound in a ionized molecule of H₂⁺?

locked in a covered container. surely the electron would be able to combine with both protons at once to produce 2 hydrogen atoms, which in turn would be able to combine and produce a water molecule.

But only if it founds an electron and an oxygen atom. Where are these?

would the energy in the water molecule become greater than it originally started (as this is against the laws of thermodynamics as far as i'm aware)

But didn't you start with an ionized molecule of H₂⁺? So how can you talk of the water molecule "originally started"? What do you mean?

or would it be water whilst unobserved and return to its original state as separate protons and electron when we look at it again?

Maybe you intended a water molecule in a superposition of 2 states one of which is the fundamental and the other is an excited one?

[dlorde]

This interpretation with multiple universes is complete garbage in my opinion, and show how wrong one can get it if is over-interprets some math in complete disregard with reality.

Why do you say it's 'complete garbage'?

[eddysciencefan (OP)]

quantum theory allows for fundamental particles to be in 2 places at once as long as we don't know the exact position. so imagine if we had a oxygen atom, 2 protons and one electron

? You intended 2 hydrogen atoms bound in a ionized molecule of H₂⁺?

locked in a covered container. surely the electron would be able to combine with both protons at once to produce 2 hydrogen atoms, which in turn would be able to combine and produce a water molecule.

But only if it founds an electron and an oxygen atom. Where are these?

would the energy in the water molecule become greater than it originally started (as this is against the laws of thermodynamics as far as i'm aware)

But didn't you start with an ionized molecule of H₂⁺? So how can you talk of the water molecule "originally started"? What do you mean?

or would it be water whilst unobserved and return to its original state as separate protons and electron when we look at it again?

Maybe you intended a water molecule in a superposition of 2 states one of which is the fundamental and the other is an excited one?

not quite sure what you mean with your first comment? in the second, my point was the oxygen atom is there to combine with, but only one electron, so i was asking if this could be bonded with both protons (due to QM) at once to complete a water molecule. third point i started with with a single electron, 2 protons and a oxygen atom, if these combine (the protons sharing the electron to become 2 separate H atoms joining with the O atom) i (possible incorrectly) assumed the mass would increase? finally i was hoping to find out on a practical level would be observed afterwards and also if it was anything else whilst unobserved.

[flr]

This interpretation with multiple universes is complete garbage in my opinion, and show how wrong one can get it if is over-interprets some math in complete disregard with reality.

Why do you say it's 'complete garbage'?

That could be a long story, but let me give you another example from a different field, on why a matematical method shall not be taken as representing a reality but rather simply a method to compute things.

In electrostatics there is so called method of image charges, which is very usefull.
For example let's consider a conductive surface which is grounded. If one bring a charge next to this conductor, the conductor will polarize and there will be generated a certain charge distribution on the conductor surface such that the total electrostatic energy is minimized.
The question is: What is the distribution of charge on the conductive surface(say a plane), sigma=f(x,y,z)?

This could be a difficult problem to solve, however there is a trick which makes the solution amazingly simple: the method of image charges.
Essentially, it put a fictitious charge on the opposite side of the plane and compute the generated electrostatic field  on each point of conductive plane from the interaction of real charge and image charge. The algebra is really high school.

Is this image charge a real thing? No! It is imaginary, if we bring one charge next to a conductor there will be no physical reality of a second charge placed on the other side of conductor, but instead there is generated on conductor a modified charge distribution.

So, if something works mathematically, it does not necessarily means that there is a physical reality of that ad-literam physical  interpretation of math. relationships.

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In my opinion that particular QM interpretation with multiple universes and multiple realities and multiple histories is simply exaggeration.

[dlorde]

... Is this image charge a real thing? No! It is imaginary, if we bring one charge next to a conductor there will be no physical reality of a second charge placed on the other side of conductor, but instead there is generated on conductor a modified charge distribution.

In my opinion that particular QM interpretation with multiple universes and multiple realities and multiple histories is simply exaggeration.

It seems to me in QM the maths and experiments show that quantum weirdness is not a convenient fiction, and quantum effects are not imaginary. The challenge is to find the most efficient interpretation that fits what the maths and experiment tells us, whether it seems exaggerated (exaggerated, how?) or not. We already accept that the universe behaves as if determined by the evolution of a complex wave function; as I understand it, MW simply suggests that particle interactions can give rise to multiple non-interfering wave fronts in that wave function. QM itself is weird and counter-intuitive; I don't think we can expect an interpretation that fits QM not to be weird and/or counter-intuitive.

What the 'reality' described by the wave function consists of remains unknown in any interpretation; it seems more reasonable to reserve judgement than to reject an interpretation purely out of incredulity.

Having said that, what would your preferred interpretation be?

[Bill S]

What the 'reality' described by the wave function consists of remains unknown in any interpretation; it seems more reasonable to reserve judgement than to reject an interpretation purely out of incredulity.

Agreed.

Reality is a difficult concept in QM.  When we state that quantum effects are real, it is important to recognise that it is effects we are talking about.  More specifically, it is the effects of QM on our observable reality.  There is abundant evidence that these effects are real, but they tell us nothing about any underlying reality. 

I believe we are free to theorise about explanations for quantum weirdness, in fact it's fun!  Obviously, if observation and maths support our ideas, they are much more likely to be taken seriously, but where QM is concerned, the question of "reality" seems largely philosophical at our current stage of understanding.

There are instances in the "classical" world in which reality can become a little blurred. 

For example: is infinity real?  Is it really possible to have an infinite amount of anything?

[lightarrow]

not quite sure what you mean with your first comment?

You wrote:
<<surely the electron would be able to combine with both protons at once to produce 2 hydrogen atoms>>. How can a single electron combine with two protons to form 2 hydrogen atoms? Either it forms an ionized molecul of hydrogen: H₂⁺ or you need 2 electrons, not one only.

in the second, my point was the oxygen atom is there to combine with, but only one electron, so i was asking if this could be bonded with both protons (due to QM) at once to complete a water molecule.

Ah, ok, sorry I misinterpreted your question. The answer is no, it can't form a water molecule, at least a stable one, it would dissociate immediately (and so it means it is energetically unfavoured); but here it depends on how much time you want it to observe it  []

[JP]

What the 'reality' described by the wave function consists of remains unknown in any interpretation; it seems more reasonable to reserve judgement than to reject an interpretation purely out of incredulity.

Agreed.

Reality is a difficult concept in QM.  When we state that quantum effects are real, it is important to recognise that it is effects we are talking about.  More specifically, it is the effects of QM on our observable reality.  There is abundant evidence that these effects are real, but they tell us nothing about any underlying reality. 

I believe we are free to theorise about explanations for quantum weirdness, in fact it's fun!  Obviously, if observation and maths support our ideas, they are much more likely to be taken seriously, but where QM is concerned, the question of "reality" seems largely philosophical at our current stage of understanding.

There are instances in the "classical" world in which reality can become a little blurred. 

For example: is infinity real?  Is it really possible to have an infinite amount of anything?

There's reasons that these are called interpretations of quantum mechanics and not called different theories of quantum mechanics.  They all make the same predictions for what we can measure, so there's no real way to tell them apart so far as we know.  (There are a few folks who claim that we might be able to, but so far their work hasn't convinced the scientific community at large).

[flr]

What the 'reality' described by the wave function consists of remains unknown in any interpretation; it seems more reasonable to reserve judgement than to reject an interpretation purely out of incredulity.

Having said that, what would your preferred interpretation be?

Interesting and difficult question.
I am pretty sure that I cannot accept the many-worlds interpretation. Where are the other universes? Are they physical universes or some indeterminate states? Do they take the same physical space as ours?
----------------
The in-determinism in QM has to do with the act of measurement and it arises from the fact that when we measure a quantum object we interact with it and alter its state.  The more precise we want to measure it, the stronger we interact with it and the less accurate we can be in determining certain properties. As such, we have to discard classical trajectories and replace them with probabilities. In other words, it is empiric and not analytic. In my opinion there is nothing inherently in-deterministic in physical laws at any level.

The hidden variable deserve some consideration because history of science indicates that no matter how well verified and how well self-contained a theory was at a time, sooner or later additional experiments will find that some pieces were actually missing and a new (more general) theory was required (see Newton vs Einstein relativity). 

----------------

[Pmb]

quantum theory allows for fundamental particles to be in 2 places at once as long as we don't know the exact position.

That is incorrect. Quantum theory does not allow that. One can't even speak of a particle being at any particular position unless its position has been measured and when its been measured its localized to single localized location. Uncertainty does not pertain to not knowing the exact position. That is a common misconcpetion. Uncertainty is a statistical quantity which is calculated from repeated measurements of the particle when the system is in particular state and that holds even when the position is known to an arbitrarily precise precission. People often confuse precise and accuracy of measurements with uncertainty.

so imagine if we had a oxygen atom, 2 protons and one electron locked in a covered container. surely the electron would be able to combine with both protons at once to produce 2 hydrogen atoms, which in turn would be able to combine and produce a water molecule.

If that were true then the system would effectly behave as if it had a net charge, which it doesn't.

[dlorde]

I am pretty sure that I cannot accept the many-worlds interpretation. Where are the other universes? Are they physical universes or some indeterminate states? Do they take the same physical space as ours?

As I  understand it (I'm sure someone will correct me if I blunder), the MWI takes the universal wavefunction seriously and says that the universe isn't just described by (and evolve according to) the wavefunction, it is entirely equivalent to the wavefunction. You, me, and everything is part of this evolving universal wavefunction. The physical world is what the wavefunction looks like 'from the inside', as it were. Every interaction (e.g. observation) can be seen as causing the combined wavefunctions of the interacting entities (e.g. observer & observed object) to become a quantum superposition of non-interacting branches of the wavefunction, numerically proportional to the probability density of likely outcomes. This branch superposition is the split into many 'worlds'.

It does mean the universal wavefunction becomes exponentially more complex every instant, but because these superposited branches are non-interfering, each path is causal and self-consistent (and is the 'real world' to its observers). I visualise this (somewhat crudely) as the way water waves from different sources can pass (through) each other without interfering, or how multiple streams of data can be encoded in a single beam of light. This analogy may be mistaken.

Anyhoo, MWI does away with the 'collapse' of the wavefunction, making it a purely subjective artefact; it resolves various QM 'paradoxes' (Shrodinger's Cat, wave-particle duality, et al), and makes QM local and deterministic. It also provides a potential explanation for things like 'fine tuning' and the Anthropic Principle. Which suggests to me that every possible universe up to the present is encoded (superposed) in the universal wavefunction according to its probability, observers will (obviously) only find themselves on paths where observers have developed, and an observer is most likely to find him/herself on a high probability path (i.e. in a high probability universe) - although even the most unlikely paths will be represented. So we're highly likely to find ourselves in one of the most highly probable universes that can support observers like us - but no guarantees.

I quite like the idea of being a mass of tiny ripples spreading through a universal probability density wavefunction; but I'm open to any other interesting interpretations.

The in-determinism in QM has to do with the act of measurement and it arises from the fact that when we measure a quantum object we interact with it and alter its state.  The more precise we want to measure it, the stronger we interact with it and the less accurate we can be in determining certain properties. As such, we have to discard classical trajectories and replace them with probabilities. In other words, it is empiric and not analytic. In my opinion there is nothing inherently in-deterministic in physical laws at any level.

I think Heisenberg would differ. The 'observer effect' is problematic as you say, but the 'uncertainty principle' describes a fundamental property of quantum systems, due to wave-particle duality. Heisenberg did once explain it in terms of the difficulty of measuring position and momentum of an electron using a photon, which probably led to the confusion with the observer effect.

I expect the MWI has an explanation for the HUP too

The hidden variable deserve some consideration because history of science indicates that no matter how well verified and how well self-contained a theory was at a time, sooner or later additional experiments will find that some pieces were actually missing and a new (more general) theory was required (see Newton vs Einstein relativity).

As I understand it, hidden variable hypotheses have been ruled out experimentally by violations of Bells inequalities. John Bell produced a theorem saying that QM effects can't be explained by local hidden variable hypotheses. He proposed that certain inequalities would need to hold for hidden variables to do the job. A number of experiments (known as 'Bell tests') have demonstrated violations of those inequalities, which means hidden variables don't cut it.

[flr]

According to MWI all alternatives histories are real in their own universe.
If so, then out there might be a universe (or a branch of the universe) where I am a king. Where is it? I want there.
Can I jump from my branch of the universe to that branch where I might be some kind of  king?
Perhaps the answer is no because branches are non-interacting?.

Can I experimentally measure anything about that branch of universe where I may be a king?
Again, my intuitive guess is that the answer could be no because the branches are non-interacting with each other. Is that so?

[dlorde]

Again, my intuitive guess is that the answer could be no because the branches are non-interacting with each other. Is that so?

I think so. The other branches aren't physically accessible/real from your branch perspective. Also, there are untold quintillions of far more likely universes, almost indistinguishable from our own, among which the more improbable universes will be like a needle in a haystack.

[flr]

The other branches aren't physically accessible/real from your branch perspective.

But then I am confused. If the other branches are not physically real and accessible from my branch, why should I believe they exists?
Is it even scientific to believe in something that is not physically real and accessible?

What is the difference between believing in 'ghosts' or 'spirits' and believing in universe branches that are not physically real and not physically accessible?