[lightarrow]

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).

Yes, but 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.

[yor_on]

What do you say about this Lightarrow?

to get a interaction you need a 'system'. Even when you define it as being something interacting with itself. That makes it one of two possible definitions, either something 'unitary' can interact with itself, or it can't be 'unitary'. If it isn't unitary, then you either have a hidden parameter, or what you call unitary can't be. If it can interact with itself then it must consist of more parts than one.

All from my own way of thinking of it, that everything 'observes' and adapts to everything (aka relations)
And welcome to the philosophy forum
=

Btw, maybe the arrow could be seen as a 'hidden parameter' here, as we have probability?

[dlorde]

... you have only changed the name of the process.

Just emphasising the semantic difference between the term in physics and the term in common usage.

What's an "interaction"?

It is the mutual effect of two objects on each other, involving the transfer of energy between objects and/or fields.

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.

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).

[dlorde]

Some minor quibbles:

...
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.

There may be no evidence for the big bang as origin of the cosmos, but neither is there any evidence for the greater cosmos itself, so the idea of a greater cosmos is open to the same objection. If you accept the possibility of the greater cosmos without evidence, is it reasonable to reject ideas concerning that cosmos for lack of evidence? The big bang as origin of the cosmos must surely remain a possibility unless there is contrary evidence. An analogy that comes to mind is a death that might be murder, but there is no evidence of it. You would not then exclude the possibility that the murderer was a woman because of the lack of evidence that a woman did it - there is no evidence that anyone did it.

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's not clear to me that this is the case, because it is not clear to what you are referring with 'infinity'; spatial extent? temporal extent? Some explanation/clarification required.

With regard to your later musings on temporal infinity, it's worth bearing in mind temporally closed models of the universe, such as Hawking's model, which describes time itself starting at the big bang. His model had the universe and time ending at a big crunch, which we now believe to be unlikely, but as he put it, if time starts at the big bang, it makes no more sense to ask what was before the big bang than it does to ask what's north of the North Pole.

Of course, there is now a variety of hypotheses about pre-big bang physics, so Hawkings model has lost its original appeal, but it seems to me that the concept of an origin of time (and possibly an end of time) could be applied to the greater cosmos (metaverse?) just as to our universe.

[Bill S]

Dlorde,  your quibbles are certainly not trivial.  Gratifying as it might be when someone agrees with you; in terms of the development of ideas, it is much more valuable when they disagree.

I take your point about there being no direct evidence for the "greater cosmos".  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.  There will probably be plenty of people who will disagree with that, and I look forward to reading their arguments, however, "given that there can never have been a time when there was nothing, it follows that there must be more to our Universe than meets the eye", because our Universe seems to be finite.

..... it is not clear to what you are referring with 'infinity'; spatial extent? temporal extent? Some explanation/clarification required.

A large part of the thrust of my reasoning is that infinity is not a very large space, and eternity is not a very long time.  In fact, making any distinction between infinity and eternity has relevance only in our limited understanding.  Time and space may have no part in the definition of infinity, but we lack the vocabulary to define it in any other way.

[Bill S]

The Infinite Cosmos  Part 2

Assuming, as, apparently, most scientists do, that the Big Bang theory is correct, our Universe must be finite; in so far as it had a beginning, but even if it could continue to expand “for ever” it could never become infinite.  Even claiming that it is expanding towards infinity is misleading.  If it can never reach infinity, in what sense can it be said to be approaching infinity; in fact it never gets any nearer.  It cannot even be likened to a hyperbolic curve which, although it never becomes a straight line, at least in theory, does, quite obviously, become increasingly straight, and therefore more like a straight line.  On the other hand a finite object that seems to go on for ever must always be an infinite distance away from infinity.

Consider the following.  Those intrepid adventurers Alice and Bob, in their respective space craft, are the only occupants of an infinite void.  Each perceives her/him self to be at the centre of the void.  There is an infinity of void extending in every direction.  This sounds like being at the centre of a sphere, but it makes no sense to describe infinity as spherical.  A sphere has, by the very fact of being a sphere, a boundary surface; infinity does not.  However far you travel in infinity, you will never reach a boundary.  A sphere has one fixed centre, but as the perceptions of Alice and Bob have already shown, there is no fixed centre to infinity, nor would it matter how far apart they were, they would still have infinity in every direction. 

What changes when Alice or Bob moves?  Any movement that either, or both, may make is movement relative to the other, not movement relative to the infinite void.  Inevitably this leads to the conclusion that whatever movement you make in infinity makes no actual difference to your position in infinity.  Before you move you are at the central point; after you move you are at the central point, but you were already there, so have you moved? 

Before we leave Alice and Bob in the void, consider one more strange thing.  Suppose that Alice and Bob are an infinite distance apart; if each moves, say, a billion light years towards the other, are they still an infinite distance apart?  Intuitively, it might feel as though they should be two billion light years closer to each other, but that would mean that the distance between them was less than infinite.  If the distance between them is less than infinite, it must be finite.  This means that something that was infinite has become finite.  Reverse their journey and something finite suddenly becomes infinite.  This is impossible.  It seems that if they are an infinite distance apart, however they may move, the distance between them will always remain infinite.  Perhaps the logical conclusion to draw from this is that in infinity, distance has no relevance at all.  This must lead us to ask if, in fact, Alice and Bob in infinity can actually move relative to each other, or if the concept of movement is simply transferred from our dimensions.

Whatever relevance distance might or might not have in infinity, it does seem that the occupants of infinity may be able to move relative to one another, but not relative to the infinite background.  There is a ring of familiarity here; this scenario has a distinctly Einstienian feel.  In 4-dimensional spacetime we can move relative to one another, but can identify no static background against which we can establish absolute motion or rest.  Given that relative movement is, at least in theory, possible in infinity, we must look at the question of time, because movement is change and change requires time in which to happen.  However, we should not lose sight of the fact that there is a major difference between spacetime, as we experience it, and infinity.  In spacetime we can identify no static background against which we can measure motion, but having said that, there is no way we can know with certainty that it is not actually possible to move relative to spacetime.  In infinity, it is infinity itself that seems to provide that background, but here we can establish that movement relative to that background is not possible.   

It seems that all we are doing is asking ever more questions, without answering any.  To attempt to answer at least some of these questions, we must look even more closely at the idea of infinity.  For the sake of simplicity the term “infinity” will be used to cover “eternity” as well; in fact, the terms are interchangeable.  In general usage eternity is simply “infinite” time, but there is a serious caveat here that must not be overlooked.  Eternity is not an infinite expanse of time; in fact, it does not involve time, the two concepts are, incompatible.  The concept of eternity as being in any way “temporal” arises from our limited ability to comprehend the nature of infinity.  Like “Flatlanders” who cannot even imagine a third spatial dimension, we try to examine infinity using only our four dimensions of spacetime.  Thus we find ourselves constantly falling back on temporal analogies and terminology, which are, at best, only of limited value, and, at worst, are downright unhelpful.   

We might wonder if we could devise some sort of thought experiment to probe eternity and time as we have just done with infinity and space.  Here, the task becomes much more difficult because as far as time is concerned we have only one observable dimension.  What is worse, we seem constrained to move in that dimension only in one direction, and, for all practical purposes, at one speed.  Of course, in a thought experiment, we can use perfect instruments and ideal conditions, so there is no bar to our travelling at sufficiently close to the speed of light for relativistic effects to become important.  In other words, we can construct our experiment in such a way as to make time dilation significant. 

If Alice could travel along the time dimension at close to the speed of light, relative to Bob, and then return, she would find she had aged less than Bob.  Unfortunately, even in our idealised experimental conditions, there seems to be no way of reversing Alice’s travel along the time dimension.  We might invoke closed time-like loops, but these come with problems of their own that might only serve to distract us from our consideration of infinity/eternity.
   

[dlorde]

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.

This is where closed or one-ended temporal systems can be considered. If time itself 'begins' when the universe or cosmos initiates (our language is inadequate for this kind of thing!), then there is never a time when there is nothing, yet it's debatable whether time is infinite in the past direction...

[Bill S]

Accepted! If time began with the Universe, then there was no time (unbounded or otherwise) before that.  However, that is little more than a semantic device.  It is no more a scientific proposition than saying  "God created the Universe", so we can ask no more questions about its origin.

In spite of such eye-catching book titles as "A Universe From Nothing"; the "nothing" always seems to turn out to be something.

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?

[dlorde]

It is no more a scientific proposition than saying  "God created the Universe", so we can ask no more questions about its origin.

True enough, although it has advantages over the God proposition, not least Occam's Razor.

But the same objection applies to your subsequent questions, none of which are scientific, yet you still ask them:

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?

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...

[lightarrow]

What's an "interaction"?

It is the mutual effect of two objects on each other, involving the transfer of energy between objects and/or fields.

It's not enough, if you want the term "interaction" to be synonimous of the term "measure" I have used in this context. See down.

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.

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).

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).

[lightarrow]

What do you say about this Lightarrow?

See my answer to dlorde. What do you think about it?

[Bill S]

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...

Before addressing the question of any useful meaning for a timeless cosmos, or any place for it in the maths, 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"?

[Bill S]

The Infinite Cosmos  Part 3

We should return to the question as to how a finite cosmos might arise out of an infinite precursor without dividing that eternal precursor, and in so doing, dividing infinity.  Three possible answers come readily to mind: (i) there is an infinite, intelligent, entity that can create a cosmos without undergoing any change in itself; (ii) the infinite precursor, although not an intelligent entity, was able to spawn a finite cosmos without undergoing change.  One must then assume that this finite cosmos gave rise to our finite Universe; and, (iii) we live in an infinite cosmos, which somehow was unchanged by the “creation” of our finite Universe.  Any of the above possible answers appears to involve a leap of faith, but we have to ask if any answer might be more logically likely than either of the others.

Theologians would undoubtedly opt for the first choice.  An entity such as this lends itself to the concept of God, the creator, whose eternal realm is outside our cosmos, but who, with a little imaginative thought, could be woven into our world view.  It is still tempting to argue that the act of creation would divide eternity into two “halves”, but this temptation may arise from our restricted view of the proposed spiritual realm. Because our only experience is of linear time, it is very difficult for us to achieve any real feeling for the nature of eternity.  There may be some mystics who can do this; Fred Alan Wolfe would have us believe there are yogis who can; and he justifies this call to belief on the basis of quantum mechanics.  Michael Talbot cites numerous examples of mystics and psychics who can experience a timeless, spaceless realm.  Julian Barbour’s “Platonia”, without resorting to mystics and psychics, paints a picture of a timeless “world” in which all movement and change are illusions, establishing that scientists as well as mystics can have profound thoughts about eternity.  In addition, as we reasoned above, movement and change seem to be possible in infinity, provided they are restricted to the frames of reference of individual occupants.   

If one were formulating an argument regarding the possible existence and nature of any causal entity that might have been responsible for the “creation” of the cosmos, it could be tempting to start the argument from a consideration of the nature of the observable Universe.  Indeed, many theist arguments have this starting point.  It is easy to think that, because progressively fewer scientists seem to believe in God, any argument that relied on observations of the Universe would become progressively less powerful as time passed.  Such a position would, undoubtedly, spring from a belief that arguments from the nature of the Universe would necessarily be based on the apparent order of the Universe, which many interpret as indicating intelligent design.  However, order and apparent design are not the only arguments that might be made from observations of the Universe, and some of the other lines of reasoning could actually become stronger with time.  For example; if one argued that there is life in the Universe, therefore its creative force must also include life; this could, a few decades ago, have been countered be the assertion that the Universe contained matter; therefore the creative entity must also have included matter.  This would necessarily have cast considerable doubt on any spiritual or supernatural claims made about the “creator”, who, at least from the theist perspective, needed to be spiritual.  To some extent, Einstein wrecked this counter argument by pointing out that matter and energy were interchangeable, and it seems easier to equate a spiritual being with pure energy than with any kind of matter.  However, things have progressed even further since Einstein, and the counter argument is by no means as secure as it would have seemed before quantum physics raised serious questions about the reality of what we perceive as matter.  Even more doubt is cast on the concrete nature of matter by the theory of the “holographic” Universe, a concept which, although it is still very much a minority view, cannot necessarily be ruled out.

If one acknowledges that the material world is not necessarily as solid as it seems to us, and if one accepts that an effect is unlikely to be greater than its cause, then it seems reasonable to argue that whatever is responsible for the existence of our Universe must contain the essential elements of our Universe in order to be able to “create” them.  For example; the Universe contains life and intelligence, therefore the “cause” of the Universe must also contain life and intelligence.  Naturally, there are many who would disagree with this line of reasoning and maintain that it is unscientific.  However, that pillar of scientific reason, Richard Dawkins, appears to support this view.     

  One of the arguments that Dawkins uses to refute the belief that the Universe had a creator is that any being who could create something as complex as the Universe would, itself, have to be very complex, and would therefore have had to evolve.  Apart from the fact that he seems to be ignoring the scientific concept of the “Boltzmann Brain”, he is, at worst, sidestepping the whole idea of eternity, and, at best, trying to apply Darwinian evolution to eternity.  It is worth repeating that eternity is not an endless succession of time, it must be something quite different, and if there is one thing that evolution needs it is time.

  Evolution provides us with the best, possibly the only, scientific explanation, not only for life on Earth, but for the existence of our Universe, as we perceive it.  Unless and until science can provide us with a better explanation than the Big Bang for the origin of our Universe, then, within this Universe, evolution rules – OK.   I am not suggesting that the evolution of the Universe from the initial singularity, or whatever the starting point might have been, was Darwinian “survival of the fittest”, but an evolutionary process can, nevertheless, be traced from the Big Bang to the present day.  The important thing to remember about evolution is that it involves change, and change, as noted above, requires time.

Asserting that there is a creator who created the cosmos might seem to lead to an infinite regression situation in which the next question must be: Who created the creator? – and so on, ad infinitum.  However, this regression can be brought to a halt at any point by invoking an eternal creator.  In the spirit of William of Ockham, we would have to concede that nothing was achieved by protracting the list of creators beyond one. 

Theists choose to call the ultimate cause of the Universe “God”, and God is interpreted in a multitude of ways by various religions, sects and philosophical schools.  Atheists, on the other hand, look for explanations that do not involve God, or any intelligent “designer”, and tend to produce their own array of explanations.  In spite of claims and counter-claims by both sides, it seems that either position is ultimately a question of “faith”.  Perhaps this is why everyone hates an agnostic.  The agnostic has seen through both sides, and, like the true scientist, is keeping all options open in case some hard evidence should be produced in favour of one side or the other.   

Returning to our list of “possible answers”; Ockham’s razor might usefully be invoked in order to dispose of the second option, which contains an “entity” for which there is no apparent “necessity”.  In reality, the second answer differs from the third only in form, and in the fact that it lets in the possibility of infinite regression.

Scientists might be more inclined to go for the third choice, particularly if they happen to be atheists.  On the face of it, the third choice seems to involve less “faith” than does the first.  However, an exploration of the concept of infinity, and how our apparently finite cosmos might be dovetailed into it, raises some interesting physical and philosophical questions. 

   The alternative to a created cosmos seems to be an infinite cosmos.  Understanding this may require some thought.  An infinite cosmos must contain everything that exists, or ever can exist.  There can be nothing that is outside an infinite cosmos: no matter, energy, space or time; no potential and no uncertainty.  Outside an infinite cosmos there can be no creation, because there can be no creator.  Nothing can be added to an infinite cosmos, because all that is, or can be, is already included in it.  Nothing can be taken away, because there is nowhere for it to go.

I guess this is a good place to make a break as there will probably be quite a few objections to this latest installment, so I'll need time to consider some possible answers.

[zbhfw]

I go by the interpretation put forth by Feynman... there is a way to calculate the probability of something happening, (the path integral), but all else is asking questions that have no meaning, and any imagined answers will probably look as silly to future generations as the flat earth theory. By the way, 'QED, the Strange Theory of Light and Matter' is available as an ebook, with a new introduction that is relative to this discussion.

[dlorde]

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).

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.

[dlorde]

... 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"?

Cantor's transfinite numbers are esoteric and interesting, but I'm not sure what you mean by "Where does that fit into 'the maths'?" - the maths is the maths of transfinite numbers (wikipedia has a reasonable stab at it). When I said there may be a place in the maths for a timeless cosmos, I was referring to the maths used in the physics of cosmology; it was just a rhetorical statement.

[yor_on]

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.

You can argue it a lot of ways, naively lift up the issue about a 'size' and ask yourself what the probability is for something without size to interact at all? That one you can use neutrons for too. But light is presumed to interact with matter. If it didn't we wouldn't be here.

And it will change angle passing that glass, depending on incoming direction. So it must interact to me unless I assume that light not to interact depending on angles, meaning a light beam 'hitting' a perfect transparent glass straight on then gets excluded from interaction. So, the question to me would be if it really can be proven that this photon in no way change momentum energy frequency passing that glass?

And that is in a way the exact same question as the one about a 'ideal elastic collision', aka light reflected from a perfect mirror.

You could also argue this way, presuming no measurable change, assuming all light quanta to be identical, then there was no glass represented from the definition of a photon interacting with matter. And that one might fit a idea of 'relations' and light non propagating. Because in such a definition we just look for a logic, we do not discuss what the logic implies when when it comes to questions about if the universe is closed or not. Neither do we ask ourselves what 'energy' really, really, is We just look at causality, experimenting on it, to then define relations.

[dlorde]

... I would from my first definition expect anything meeting another object to interact, especially if passing through it.

As already mentioned, there is an amplitude for photons to pass through the glass without interacting.

[yor_on]

Want to expand on that one dlorde?
Using my definition it either interact, meaning that it will differ, or it doesn't. If there is a measurable change then that should be a result from a interaction, and that includes everything that differ from how we define it to have behaved before, including its propagation.

[yor_on]

Using Feynman's many paths then I would say that that is a result from statistics, defining probabilities. That to me is the same concept as I described when discussing light as non propagating. We use logic to define it, and if that logic won't fit a macroscopic definition then it doesn't matter, as long as the logic makes sense and give us a prediction. From it you can, or you can't, 'prove' how it really should be, also depending on what experiments you can imagine up to define your hypothesis. And to me the most important things there should be the experiments and the logic, if that works then the theory can wait a little Because a theory is just as good as our preconceptions, and we all have such.