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This could be a poll, but there would be too many options. What interpretation of quantum mechanics do you subscribe to (e.g. many-worlds, consistent history, deBroglie-Bohm)?
The most commonly taught and widely accepted interpretation is that of the Copenhagen Interpretation. Do you feel this is a just treatment of our universe? Do you believe that the wave function describing a system, when observed, collapses into a discrete eigenstate?
Perhaps wave function collapse is a human construct?
All the interpretations tend to be a bit mystifying to non-scientists like me, ...
...but a distillation of the De Broglie-Bohm interpretation invites some comments.
The cosmos in which we live is infinite;...
... not only is every part in contact with every other part, every part is the whole.
It is not sufficient to say that everything that can happen happens, ...
In infinity there can be no change, no progression and no differentiation in time or space.
Change, movement and the passage of time that we observe is an illusion arising from our 3 + 1 dimensional perspective.
Quantum mechanics is a window into the infinite, ...
I'm partial to the many worlds interpretation because I find it philosophically fascinating. But in practice, I'm very much an empiricist, so I stay out of fights over which interpretation is best: they all agree with observation.
Don't know exactly what you mean but if you mean that the collapse is *caused* by the human act of observation (the man who opens the box to see if the cat is dead or alive), then it's not. The collapse is caused by the act of measurement.
Quite. And an 'act of measurement' occurs for any interaction with the system (e.g. any particle interaction). Observers not necessary. The idea that an 'observation' or 'measurement' must involve a conscious observer seems as popular an error as the idea that the Uncertainty Principle is a consequence of the Observer Effect.
I take it that you're familiar with it then?
That is not known to date. It's possible that the universe is spatially closed, which means that it's finite in extent.
That is incorrect. We are not in contact with most of the universe.
There is no way to prove such a think like that.
Almost everything is chaning with time so how can you say that there can be no change at all? Is that what you really mean to say?
I don't know where you got that idea but it's quite wrong. There are very few physicists who would agree with such a statement. Except, of course, Julian Barbour who thinks that time is an illusion. Most, if not all, physicists don't accept that view.
Huh? Why? You're really confusing me. Please explain where you're getting these notions from or at least justify them for us
M'man! You're awesome! That is precisely the way I see it. In fact the paper by Bryce de Witt that I posted a link to above addreses that exact thing. You should give it a read. I think that you'd like it.
The way I think of the Copenhagen definition is that you are part of a experiment. The experiment per se are not actively involved in setting parameters and limitations. You do that, before, also defining a outcome by it. And that's the 'part' I'm referring to there. The cat is a beautiful example on that you don't know a outcome, but your choice of parameters and limits will still make a difference. And where they end you still should, practically seen, find relations defining a outcome doing some forensic work on any 'real experiment'. You can't assume consciousness to define the 'mechanics' of a universe unless you define the universe itself to have that consciousness. Although it will still be correct to define it such as 'relations' defining a outcome, including you making your choice of experiment, as well as observation..
Quote from: lightarrow on 16/05/2013 12:47:46Don't know exactly what you mean but if you mean that the collapse is *caused* by the human act of observation (the man who opens the box to see if the cat is dead or alive), then it's not. The collapse is caused by the act of measurement.Quite. And an 'act of measurement' occurs for any interaction with the system (e.g. any particle interaction).
... you have only changed the name of the process.
What's an "interaction"?
For example, when a beam of light is bent, without absorption, by a glass prism, does the beam "interact" with the glass or not? Explain why yes or why not.
...I suppose we could suggest a big bang as the origin of the cosmos, but as far as I am aware there is no evidence to indicate that this might be the situation, so we would simply be plucking a theory out of the air, which is not the best foundation for anything resembling serious enquiry.
In mathematics we can have more than one infinity, but in reality, infinity must be everything; if it does not include everything, it is not infinite. If we postulate more than one infinity, then neither is infinite, because the contents of one infinity must always be excluded from the other; which is nonsense.
..... it is not clear to what you are referring with 'infinity'; spatial extent? temporal extent? Some explanation/clarification required.
One of the ideas that is central to my thinking is that if there had ever been a time when there was nothing, there would still be nothing now.
It is no more a scientific proposition than saying "God created the Universe", so we can ask no more questions about its origin.
If there was nothing before the Universe; was there an infinity of nothing?If not: what came before the nothing?Why might it be preferable to imagine that there was nothing, rather than that there was a timeless cosmos?Which of those is, logically, more likely to give rise to a universe with space and time?
Quote from: lightarrow on 18/05/2013 11:48:46QuoteWhat's an "interaction"?It is the mutual effect of two objects on each other, involving the transfer of energy between objects and/or fields.
QuoteWhat's an "interaction"?It is the mutual effect of two objects on each other, involving the transfer of energy between objects and/or fields.
QuoteFor example, when a beam of light is bent, without absorption, by a glass prism, does the beam "interact" with the glass or not? Explain why yes or why not.Yes, it interacts. Considered as a wave, the frequency remains constant but the phase velocity is changed entering the glass; the refractive index of glass varies with frequency, so the change in phase velocity of the different light frequencies varies, resulting in the frequency dependent refraction & splitting of the beam. Considered as particles, the photons interact with the electrons in the glass, by scattering, absorption, and re-emission (see Feynman's 'QED', ch.3, p.107).
What do you say about this Lightarrow?
Incidentally, I'm not sure the idea of a 'timeless cosmos' has any useful meaning, but maybe there's a place for it in the maths...
But if the light beam is made of single photons, a photon's wavefunction doesn't collapse after having passed through the glass prism, so that "interaction" is not a "measure" of the quantum state of the photon (in particular, of its frequency).
... consider Cantor's mathematical infinities. His countable and uncountable infinities found their places in the maths of the time, and have remained there. What is rarely considered is that he discovered that there existed an infinity of these infinities. Where does that fit into "the maths"?
... I would from my first definition expect anything meeting another object to interact, especially if passing through it.
Quote from: lightarrow on 19/05/2013 14:20:04But if the light beam is made of single photons, a photon's wavefunction doesn't collapse after having passed through the glass prism, so that "interaction" is not a "measure" of the quantum state of the photon (in particular, of its frequency).If you read Feynman (QED pp.101 & 107), you'll see he explicitly describes the scattering interaction as the photon being absorbed by an electron and a new photon being emitted. If you prefer the wavefunction collapse interpretations, the absorbed photon's wavefunction clearly must collapse. There is a probability amplitude for photons to pass through the glass without interacting, but for the observed refraction, the scattered photons are also required. As already mentioned, the frequency of the light doesn't change, but its phase velocity does (depending on frequency). The use of 'measure' in physics generally refers to an observation (collapsing the wavefunction if you like), but in QM, any interaction has this effect, so 'measure' is the subset of interaction that involves observation. That's all I was saying.
Yes Lightarrow To me it's a question of what 'reality' should be seen as. The first thing I would like to measure is if the photon would differ for passing that glass. If it won't, then that need a explanation, as I would from my first definition expect anything meeting another object to interact, especially if passing through it.
So our partial knowledge will always be zero.
Want to expand on that one dlorde?
If that were a qm measure, why you can't say which is the photon's energy after coming out of the prism?
As you know, infact, the photon's wavefunction is still in the same superposition of frequencies which had the photon before entering the prism).
If it was a measurement, you could know. Like I said, measurements are the subset of interactions where an observer is involved.
I have some problems with the notion of an observer being involved. One has to define "observer" and I'm sure that we can all agree that the universe existed before observers where here and that life existed before it knew how to make an observation.