If one describes the whole universe this way, there is nothing logically inconsistent within the math of saying the whole 4 dimensions (or however many dimensions you have in your system) physically exist (in some substance intuition sense) as one 4 dimensional block. — boethius

Within the math of classical mechanics.

In Quantum mechanics it is very much inconsistent. Because there are 2 alternatives in quantum mechanics:

1- The wave function collapses, in which case, different behavior will be seen as a result of the collapse to if the wave function didn't collapse (this is the whole point of the double slit experiment). Thus, assuming that the wave function will collapse will not yield the same results as assuming it will not collapse (the former means a striped pattern, the latter means an interference pattern)

2- The wave function "doesn't collapse". Instead, it collapses, in every possible way, each in its own universe. So "overall it didn't collapse". That's MWI.

And a bunch more but those are really the only two being discussed right now.

Also the 4 dimensional analog of a cube is called a tesseract.

I didn’t mean you’re not well-read generally, just to do some more reading in regards to this topic. Seriously, get hold of Manjit Kumar’s Quantum. It’s a great book on this topic. Have a read of some of the reviews.

:up: Hey, thanks for the feedback, and your contributions.

Maybe I will.

And to you I'd suggest you pay more attention to when someone is saying "Conscious attention is the only thing that can cause wave function collapse" vs that "Conscious attention causes wave function collapse" or even just "The wave collapses when we consciously measure where it goes". Because so far you've mostly given quotes and articles saying the last 2, claiming they say the first.

Cheers. Thanks for the discussion but I don't think we'll get anywhere anymore.

You’re welcome. Overall it was a very good discussion and thanks for it.

Within the math of classical mechanics.

In Quantum mechanics it is very much inconsistent. Because there are 2 alternatives in quantum mechanics: — khaled

Having multiple interpretations of things does not create inconsistencies.

If you show a parabola equation to a mathematician, there's lot's of interpretations available such as an arch of a particle through space (approximately so), or a string suspended between two fixed points (approximately so), or a shape you have or intend to draw, quadratic growth of some value, or maybe we don't care about the parabolic shape but want to solve for it's roots which will tell us the information we want to know.

Multiple interpretations does not create mathematical inconsistencies.

If I tell you "6", it's not a mathematical inconsistency that I could be talking about 6 electrons or 6 bananas or just the number 6.

Likewise, even if we assumed quantum mechanics does not lend itself to a "block universe" interpretation (which it does), the block universe is not the only interpretation of classical mechanics. We can interpret classical mechanics as representing particles that really do move through time.

All this is getting off topic however, as the analogy that a block universe interpretation of physics is only problematic because we are conscious of the present and time clearly flows in one direction to us.

However, for those curious, the block universe interpretation is as easy in quantum mechanics as classical mechanics. There are just many more paths through the block associated with any particle. If we want to add "wave function collapse" (which the point of contemplating the "cosmic wave function" is that we don't need to ever add a wave function collapse, if we remove the hypothesis of conscious observers that see definite things) then the many potential world lines associated with a particle collapse in the block to the, if not one location, then "smaller region" anytime the wave function collapses in this block universe.

Again, the only reason to postulate "time" as some sort of changing singular experience in our quantum block universe is if we want to contemplate the idea that some of the "particle world lines" represent a conscious being that experiences "time" as some changing singular experience. However, if we had no observers in our quantum block universe there is nothing in the math that would tell us time is some special thing as we understand time to be in our experience.

Having multiple interpretations of things does not create inconsistencies. — boethius

Sigh. Read the whole comment please. I show why one of the interpretations (the one we happen to be discussing) is inconsistent with that.

However, for those curious, the block universe interpretation is as easy in quantum mechanics as classical mechanics. There are just many more paths through the block associated with any particle — boethius

This is MWI. Which we were not talking about.

If we want to add "wave function collapse" (which the point of contemplating the "cosmic wave function" is that we don't need to ever add a wave function collapse, if we remove the hypothesis of conscious observers that see definite things) then the many potential world lines associated with a particle collapse in the block to the, if not one location, then "smaller region" anytime the wave function collapses in this block universe. — boethius

Great. Now the question becomes, do we need a conscious observer for this to happen, or can it happen on its own. If given you experiments that show it happens on its own. In addition to the simple thought experiment, that if you want to admit that minds/consciousness require brains, and brains require definite (collapsed) electrons and atoms to make, then it’s not possible to get consciousness unless you already have some collapsed stuff. So consciousness can’t be necessary for collapsing wave functions.

Again, the only reason to postulate "time" as some sort of changing singular experience in our quantum block universe is if we want to contemplate the idea that some of the "particle world lines" represent a conscious being that experiences "time" as some changing singular experience. However, if we had no observers in our quantum block universe there is nothing in the math that would tell us time is some special thing as we understand time to be in our experience. — boethius

Back to MWI. “Multiple world lines” is MWI. Collapse (what we’re talking about) is a single world line.

Sigh. Read the whole comment please. I show why one of the interpretations (the one we happen to be discussing) is inconsistent with that. — khaled

There is no inconsistency with MWI. You just have the block universe of all the possible universes. You have mathematically exactly what I described as the "cosmic wave function" that contains all the possibilities. MWI and cosmic wave function are mathematically the same, only in cosmic wave function I am removing the postulate that there are any conscious beings in this mathematical structure that experience anything, so "all the quantum states" can just happily remain in one quantum block universe where time has no special meaning.

It's not really useful to try to visualize the quantum block universe since there's many more dimensions for field strengths and directions as well as more dimensions representing the probabilities (either mapped onto new dimensions or just left in complex value form; a mathematician investigating this structure won't care that values are complex).

As I say, it's off topic as my point is simply to bring in the analogy that the only "problem" for block universe interpretation of physics equations when we remove "time" as something special that is experienced ... is the fact that we do believe the universe has conscious observers that do in fact experience time.

Great. Now the question becomes, do we need a conscious observer for this to happen, or can it happen on its own. — khaled

This is what I am explaining; the only way for us to resolve this question scientifically, is to setup an experiment and then for us to both become conscious or the result. If we setup the experiment and then never look at the results (i.e. just keep the lid of Schrödinger's box closed) then we don't know if the wave has collapsed or not because we haven't looked.

That's just how science works, if we don't observe we cannot say what the "real state" of Schrödinger's box is; it is as consistent to say it is in some definite state as to say it remains in the quantum superposition of all it's possible states we might observe when we open the box. One is free to believe the quantum state had already collapsed multiple times since we closed the box ... one is free to believe the quantum state has not at all collapsed since we closed the box; both views will result in the same predictions (we both have the same information of the state of the box when it's closed, we both have the same equations, we will both arrive at the same possible states and probabilities for what we'll see when we open the box; what is "really in the box" when we aren't looking is a unfalsefiable claim, as to falsefy a claim about what's "really in the box" when it's closed, we need to open the box and look and so it's no longer closed).

There is no inconsistency with MWI. — boethius

Sort of. But we weren’t talking about MWI. We were talking about collapse and what causes it. There is an inconsistency between “multiple world lines” and “collapse”.

This is what I am explaining; the only for us to resolve this question scientifically, is to setup an experiment and then for us to both become conscious or the result. — boethius

No we don’t. We need to become conscious of the consequences of the result. Such as cookie or no cookie. Would you call that “becoming conscious of the result”?

what is "really in the box" when we aren't looking is a unfalsefiable claim, as to falsefy a claim about what's "really in the box" we need to open the box and look — boethius

No. We only need to check if any cookies have been dispensed yet. As long as none have, the car is alive. When one is dispensed. The cat is dead.

We can definitely tell the state of the cat. Without observing the cat.

MWI will have you believe that for each point in time, a new universe is created where the cat died and a cookie was dispensed. Note that EVEN THERE the wave function has collapsed, just in different universes. You don’t have a single block universe with multiple paths, no, you have every possible block universe with a single path each. That’s what MWI is.

On the other hand, all collapse theories have a single universe where the wave function DOESN'T collapse until measured. Again, in MWI, the wave collapses in every possible way (so overall it “doesn’t collapse” if we merge all the block universes). Without MWI we have to figure out when the wave collapses. And I’m saying it is very easy to prove that it collapses without any conscious interference, simply by interacting with a measuring device (or macro or object in general)

Again, address this: Consciousness evolved yes? In order for that to happen we needed to have collapsed, well defined molecules at least yes? And eventually after enough time a conscious thing evolved from these molecules yes?

Then how can consciousness be a requirement for wave function collapse? If it was, it would’ve never evolved.

Sort of. But we weren’t talking about MWI. We were talking about collapse and what causes it. There is an inconsistency between “multiple world lines” and “collapse”. — khaled

There's no wave collapse in MWI, as the idea there is all possibilities really exist in some physical definite state and new universes pop into existence every time there is a quantum fork in the road.

"Wave collapse" is the idea there's only one universe that doesn't split at every quantum fork in the road, but the possibilities collapse into one path going forward.

In both MWI and "wave collapse" theories, if we "setup", or just imagine, a cosmic wave function at the beginning of the universe will have the same mathematical structure. It's just in one interpretation if we go "forward in time" with our equations we see a range of possibilities and "predict" one of those possibilities will "actually happen" for observers at that moment in time. Whereas in MWI we go forward in time with our equations and we see the same possibilities but assert every possibility corresponds to a real "universe" (which should really be called "subverse" to the real universe of all these possibilities actually existing).

No we don’t. We need to become conscious of the consequences of the result. Such as cookie or no cookie. Would you call that “becoming conscious of the result”? — khaled

Science works through consciousness. We formulate questions, we formulate answers to those questions, we try to "prove" an answer is right or wrong through experiments. If we imagine unconscious rocks sitting in a pond, they cannot "do science".

It simply makes no sense to say we will setup an experiment but neither of us will ever become conscious of the result, and that will settle, in a scientifically meaningful way, the issue at hand.

This is just what "science" means. If you setup your cookie experiment but never look at the results, but assure me the cookie is definitely either there or it isn't even if you don't look, I'll ask "how do you know". The only way for you to "know" is to go and check, but you're claiming to know even if you don't check.

We can definitely tell the state of the cat. Without observing the cat. — khaled

We cannot know the state of the cat without observing the cat. We can know it's possible states based on initial conditions when the lid of the box is closed, to know it's state afterwards we need to look in the box. We can do that by physically opening the box, we can do it by running an MRI of the box, we can do it by setting up a detector for cosmic rays debris that travel through the box, we can take the temperature of the box and conclude the cat is dead if the box is too cold or on fire if the box is too hot, but each way we might get information on the state of the box requires observations. If we want to have a sort of "pure" cat killing experiment, we would make our box a light year on each side and place the cat in a suitable smaller livable box in the middle with our experiment; this way we can be certain that no information is "leaking" out about the state of our cat.

There's no wave collapse in MWI, as the idea there is all possibilities really exist in some physical definite state and new universes pop into existence every time there is a quantum fork in the road. — boethius

What exactly is a "quantum fork"?

What exactly is a "quantum fork"? — SolarWind

Usually in these discussions what I am calling "a fork in the road" is called a branch in a graph of possible state changes.

What it means is simply that when a "wave collapses" and a value previously represented by a range of possibilities becomes one possibility (which is not really one possibility, it becomes just a more constrained range than it was before, as we don't observe particles at "points" but in a region, such as photons hitting a camera sensor we just know which region the photon hit, but not the exact location).

In multiple worlds interpretation there is no wave collapse of the possibilities into more constrained possibilities, but simply everything that can happen does happen in multiplying real and equally physical universes. Every time the universe splits to follow different possibilities new branches appear in the tree of real possibilities that constantly proliferate at a considerable rate, actualizing every possible state of the universe.

We've been recently debating the idea of wave collapse relating to consciousness, as opposed to multiple worlds where no "probability waves" ever collapse.

There are other possibilities, however. Earlier we were discussing hidden variables. Bell inequalities is about local hidden variables, but doesn't exclude non-local hidden variables. Everything could still be fully determined by non-local hidden variables, which, if we knew we could use to fully predict any quantum process. Based on quantum physics as it seems to be now, it's difficult to imagine, even in principle, being able to actually know these hidden variables. However, we can still nevertheless conceive of these hidden variables existing in some other hidden variable dimension that we could probe with the right apparatus to arbitrary precision. Such "hidden variable dimensions" being discovered and accessible to arbitrary precision to predict the exact results of quantum processes (not just the probability distribution of where each particle is likely to land, but exactly where each particle will land to arbitrary precision, constrained just by size of apparatus, for instance) would return physics to a Newtonian world view that everything seems to be in a definite state and larger asparagus gets us more precise results without limitation (in quantum physics as it is, there are fundamental limits to probing values: measure position precisely and you can't measure momentum precisely at the same time; measure too precisely and you create black holes and can no longer see what happens inside those black holes).

So, "likely" hidden variable dimensions, if they exist, we can't access them. However, there's nothing the matter in principle to suppose quantum processes follow some fully determined path without any randomness, due to smaller states we are unable to access.

Next to "consciousness based wave collapse", multiple worlds, full determinism, there are other ideas such as "entropy based wave collapse" as well as "wave collapse just happening spontaneously".

What it means is simply that when a "wave collapses" and a value previously represented by a range of possibilities becomes one possibility — boethius

Only within a certain stochastic process governed by entropy, surely?

Only within a certain stochastic process governed by entropy, surely? — Shawn

Yes, this is the main problem with "entropy collapse" as I understand it. Entropy is (in it's classical sense) a macro statistical property resulting from fundamentally quantum process (as is temperature, a related macro property to entropy), so it doesn't really make sense in the usual way entropy is understood to say it can collapse wave functions.

So, some quantum version of entropy needs to be made for it to relate to quantum wave collapse. The one's I've seen are basically just some statistical probability of wave collapse based on number of particles or amount of information. Which can of course be postulated without any conflict with the standard model as it is, but the hope of such theorists is generally that there is some experimental difference that can be detected.

Usually in these discussions what I am calling "a fork in the road" is called a branch in a graph of possible state changes.

What it means is simply that when a "wave collapses" and a value previously represented by a range of possibilities becomes one possibility ... — boethius

However, splitting into different possibilities again involves the definition of measurement, which is precisely what is to be avoided in the MWI. If I have defined what exactly a measurement is, then I can simply choose the Copenhagen Interpretation. The MWI would then be superfluous.

But, entropy makes everything quite a bit more deterministic. Whilst QM remains elusive for high variance in temperature gradients for atomic elements locally, and even non-locally, yea?

However, splitting into different possibilities again involves the definition of measurement, which is precisely what is to be avoided in the MWI. If I have defined what exactly a measurement is, then I can simply choose the Copenhagen Interpretation. The MWI would then be superfluous. — SolarWind

I'm not sure I agree. MWI seems to me to still have the problem of when these worlds actually "split"; it's easy to say "when something is measured as is understood in the standard model", but if nothing is measuring anymore it doesn't seem to me clearly defined when universe splits are supposed to happen; whenever something "could have" been measured. I believe there's also the "continuous" split, at least in some sense, idea and interference patterns then need to be interpreted as these continuously splitting universes interfering with each other. Of course, you can (as with all these interpretations) just say "in a consistent with the standard model".

But to be clear, science does not have a measurement problem. I can take this clock and measure something taking 45 seconds to happen. I can take this ruler and I can measure this thing to be 18cm. I can take something and weigh it to read 40 grams. Likewise, I can make an apparatus in a precise way and read out measurements of the apparatus. I can predict how this precise apparatus will behave (what I will see in it's measurement output) using sophisticated mathematics and knowledge of how I built my apparatus and what state it will be in when I turn it on.

The "measurement problem" is not a problem scientists who measure things face, but rather a problem of people trying to take the person measuring out of the measuring and substituting some collection of particles or what-have-you, which of course can always be hypothesized to be in a superposition of all their possible outputs until someone bothers to check and report back that's not the case.

But, entropy makes everything quite a bit more deterministic. Whilst QM remains elusive for high variance in temperature gradients for atomic elements locally, and even non-locally, yea? — Shawn

Obviously, this whole conversation is in the context that there is no theory of quantum gravity, no real understanding of what dark matter or dark energy really "is", incompatible measurements of the Hubble constant that should be compatible, etc.

So, definitely some future new physics could re-frame all these questions totally differently. No reason in principle, if there are hidden variables in some other dimension, that we couldn't access them somehow.

The only point I'm trying to defend is my view on the idea we can "know" what reality is like before we look to see what it's like. Any such theory is speculative in my view. I don't have a problem with speculation though. Can be mind expanding and lot's of falsefiable scientific predictions originated in what may appear as speculation; so, I'm not here to judge for sure what's "really speculation" or "really totally not", but I will of course make the challenge to anyone claiming to know these things we have been discussing.

But in short, I haven't looked in detail about quantum entropy concepts other than combination of micro-states in an essentially classical sense.

The "measurement problem" is not a problem scientists who measure things face, ... — boethius

Of course not. According to the Schrödinger-Newton-Equation, even the cat is big enough to cause a collapse. Together with the Bohmian Mechanics and the entanglement of measuring object and measuring apparatus (e.g. the cat) everything is explained. The cat is already in a defined state before looking. And the moon is also there when nobody looks. Nobody needs MWI.

There is no experimental evidence that something just needs to be "big enough" to cause probability wave collapse.

"Big things" we assume are in definite states even if we don't look, only because we are big and perceive definite states. There is nothing in quantum mechanics that forces one to start "wave collapsing" once a certain amount of terms and time have been added to describe a system. There is nothing in the mathematics of quantum mechanics (as understood apart from the behaviour of apparatusses and having some independent existence from such apparent behaviour) that prevents adding as many states of things as one wants (as long as the it coheres with the previous states) and then simply propagating the resulting total state forward as far as one wants. The only reason we need to assume probability distributions collapse to "one world" is because we are conscious of only a single world; without this foundational assumption going into things, the mathematical structure of quantum mechanics would not lead us to invent it (i.e. conscious beings perceiving a single possibility) and without this constraint a mathematician that doesn't know "what it's about" I would expect would be perfectly happy with a bunch of parameters and variables, equations, ways to solve for one variable (or then the constraints on that variable) given other constraints on other variables etc.

In other words, if you took the math and removed all the meaningful labels like "time" and so forth, you could ask the mathematician to solve for something, for instance what to us is question about, given some initial state, the probability distribution of a particles position after some time t, but is just a "math problem" to the mathematician. The mathematician would provide whatever solutions exist for the question, which would be the constraints on variables in question (x,y,z coordinates and some additional value representing probability for each coordinate), likely in some equation form. What I contend the mathematician is unlikely to do is add the postulate that the probabilities "collapsed" in some sense on the way to the final answer, but rather would just plug in the provided parameters and constraints (i.e. the fundamental constants and whatever values for initial conditions we provide) into the equations and solve for the question. This would be the process no matter how much information we provide in terms of initial conditions or then constraints at, what is to us, future times which to us represents "measurements", but to the mathematician is just additional constraints to take into account to solve things without the need to imagine the solutions represent anything real at all.

Adding a lot of information about states would make the work the mathematician needs to do exceedingly long and difficult, but I contend at no point would the mathematician postulate wave collapse happening nor even postulate that when answers are given (constraints on variables provided constraints on other variables) that somehow a single range of one or more variables, what we would call possibility (i.e. the photon hitting a particular region of a sensor apparatus), is "special" in a sense of actually happening.

If this process (that for the mathematician is just math and doesn't represent reality in anyway) results (what is for us who understand how the variables are usually labeled) in the solution to a question about interference patterns in a double slit experiment, the mathematician will solve for the pattern and is happy to provide it, but there's nothing in the math that implies "one spot" in the pattern must logically "happen". The math doesn't logically lead to special spots where something actually happens, that is the core of the quantum mystery (why rejecting hidden variables, which is not the same as rejecting merely local hidden variables, is as problematic as accepting them; for if they do exist, where are they, and if they don't exist, then how do particles / quantum states "choose" where they end up, it seems then "pure uncaused spontaneity" ), there's no logic to where things actually happen, only the probability of happening, and so provided only the logic without context of an experienced reality we are talking about, a single reality does not jump out from the math as a logical necessity. It's mostly just a lot of integrals in abstract spaces which mathematicians solve for fun all the time without suddenly deciding certain values represent probabilities of something actually happening in some sense in the real world, and much less be led to add the postulate that "constraining events" (what we'd call wave collapse) randomly happen along the way to the final answer to a given question (these additional "constraining events" don't change the answer as it's unknown what will be constrained in such a hypothetical constraining event, and so adds no additional information to the initial conditions).

The reason quantum physics doesn't work like this mathematical exercise is because physicists add additional constraints by measuring things in the real world: the real world, not logic, provides this additional information that makes it reasonable to constrain a quantum model at some real time t to reflect what was actually measured. Logic does not even provide some necessary extrapolation from the equations of quantum mechanics that there must be "measurements"; hence, why all sorts of speculation is compatible with it. However, I'm sure you would agree that it is the equations of quantum mechanics that are extrapolated from the single world we see, not the other way around.

What I contend the mathematician is unlikely to do is add the postulate that the probabilities "collapsed" in some sense on the way to the final answer, but rather would just plug in the provided parameters and constraints (i.e. the fundamental constants and whatever values for initial conditions we provide) into the equations and solve for the question. — boethius

That's what I might do. The metaphysics could be fun, though. :cool:

There's no wave collapse in MWI, as the idea there is all possibilities really exist in some physical definite state and new universes pop into existence every time there is a quantum fork in the road. — boethius

“Really exist in some physical definite state” = collapse.

"Wave collapse" is the idea there's only one universe that doesn't split at every quantum fork in the road, but the possibilities collapse into one path going forward. — boethius

Correct. And MWI is the idea that this is what happens, for each possible universe. Again, you have each possible single path block, not a single multi path block (though that’s what you get if you were to superimpose all the blocks on each other)

It's just in one interpretation if we go "forward in time" with our equations we see a range of possibilities and "predict" one of those possibilities will "actually happen" for observers at that moment in time. — boethius

Yup. So a single path.

in MWI we go forward in time with our equations and we see the same possibilities but assert every possibility corresponds to a real "universe" (which should really be called "subverse" to the real universe of all these possibilities actually existing). — boethius

So a single path, for every possible path a world.

This is just what "science" means. If you setup your cookie experiment but never look at the results, but assure me the cookie is definitely either there or it isn't even if you don't look, I'll ask "how do you know". The only way for you to "know" is to go and check, but you're claiming to know even if you don't check. — boethius

No the point is this isn’t the “result” of the experiment. The variable we want to examine is whether or not the wave function can collapse without our conscious interference. If we get a cookie, where was the conscious interference? We definitely didn’t measure which slit the electron went through. And we didn’t interpret the results on the screen. All that was done by things that aren’t conscious. Yet in the end, when we look at the cookie dispenser, it won’t be “in a superposition of dispensing and not dispensing a cookie” it will either dispense or not dispense a cookie. Based on that we can know whether or not collapse happened without measuring which slit the electrons are going through. That’s the point. Same with the cat. All you’d need is a cookie dispenser there too to know specifically whether or not the cat is alive without observing the cat, just the dispenser.

And, again, address the historical argument:

Again, address this: Consciousness evolved yes? In order for that to happen we needed to have collapsed, well defined molecules at least yes? And eventually after enough time a conscious thing evolved from these molecules yes?

Then how can consciousness be a requirement for wave function collapse? If it was, it would’ve never evolved. — khaled

Again, address this: Consciousness evolved yes? In order for that to happen we needed to have collapsed, well defined molecules at least yes? And eventually after enough time a conscious thing evolved from these molecules yes?

Then how can consciousness be a requirement for wave function collapse? If it was, it would’ve never evolved. — khaled

I hate to re-open this issue, but you keep asking this. (Again this is from my knowledge, if someone with a degree in mathematical physics says I have it wrong, I will defer to them by all means.) But I think the so-called 'wave function collapse' is not necessarily something that happens objectively - it's not a literal change of state. It's not that matter exists in some non-collapsed state, waiting for someone to measure it, so it can collapse and thereby begin to exist. The issue arises from reconciling the wave-function equation, which describes the state of the object before it is measured, with the act of measurement. What is potential becomes actual with the measurement. I think this is the meaning of QBism, 'quantum baynsieanism':

According to QBism, many, but not all, aspects of the quantum formalism are subjective in nature. For example, in this interpretation, a quantum state is not an element of reality—instead it represents the degrees of belief an agent has about the possible outcomes of measurements.

I've been reading a well-known paper by John Wheeler about the delayed-choice experiment ('Law without law'). He says:

It is wrong to think that the past is "already existing" in all detail. The "past" is theory. The past has no existence except as it is recorded in the present. By deciding what questions our quantum registering equipment shall put in the present we have an undeniable choice in what we have the right to say about the past.

What we call reality consists of a few iron posts of observation between which we fill in by an elaborate paper maché constructions of imagination and theory.

Again, I think the underlying point is that reality is no longer conceived of being 'out there' completely independently of ourselves. As Wheeler says, we 'construe' it in a particular way - there are objective elements - the 'iron bars' of observation - but also imagination and theory.

Also have a listen to Andrei Linde's response to the same question. Linde is the physicist who came up with the original idea of 'inflation' in respect to Big Bang cosmology. (The video is bookmarked to the specific question but if it doesn't work it's around 6:06)

I think the so-called 'wave function collapse' is not necessarily something that happens objectively - it's not a literal change of state. It's not that matter exists in some non-collapsed state, waiting for someone to measure it, so it can collapse and thereby begin to exist. — Wayfarer

That’s one interpretation. I’m not sure what it’s called but I also don’t think it makes sense. If this was the case, then you’d just expect the double slit experiment to always produce 2 lines. Because after all, the matter already exists, completely collapsed, and doesn’t need measurement.

It’s precisely because matter can exist in an uncollapsed state that it has different behavior when collapsed vs uncollapsed.

Also this sounds closer to what Andrei Linde is saying. He’s asking if consciousness can be required for matter to exist in any objective sense, OVER just being something required for our description of matter 10:20

The issue arises from reconciling the wave-function equation, which describes the state of the object before it is measured, with the act of measurement — Wayfarer

But I thought you just said that there is no difference between before the matter is measured and after, when it comes to the physics itself. Only what we can say about it.

If that’s the case how come there are direct physical consequences to both, over what we can just say. For example, if you do the double slit experiment on a screen that begins to burn when hit by enough electrons, the screen would burn in whichever pattern is produced, either 2 stripe or interference pattern. There is a real consequence here. We can check the screen after to find out which pattern “really happened” more than just which pattern “we can say happened”

You say that quantum mechanics is “epistemological” in a sense. That all it does is express what we can say about what the matter is doing, but the matter itself already knows what it’s down, doesn’t need anyone to collapse it.

If that’s the case, then you’d expect that doing the double slit experiment, without the measuring device, would produce an interference pattern, but the screen would burn in a 2 slit pattern. Because after all, quantum mechanics only represents “what we can say” and since we haven’t measured anything, we would see an interference pattern. But since it’s only about “what we can say” and the matter itself doesn’t need any measuring it already has a definite state (that we just don’t know) then it will “actually” produce a 2 stripe pattern.

Maybe I’m talking out of my ass but do you get the point I’m getting at? If the measurement problem was purely an epistemological problem, then you wouldn’t expect “uncollapsed” and “collapsed” matter to act differently, because “uncollapsed” matter is just collapsed matter but we don’t know how it’s collapsed.

What we call reality consists of a few iron posts of observation between which we fill in by an elaborate paper maché constructions of imagination and theory.

But how did “we” arise without iron posts or paper maché? If we’re required for reality (the objective world) to exist in any resolved way, how did we ourselves come about?

But I think the so-called 'wave function collapse' is not necessarily something that happens objectively - it's not a literal change of state. It's not that matter exists in some non-collapsed state, waiting for someone to measure it, so it can collapse and thereby begin to exist. The issue arises from reconciling the wave-function equation, which describes the state of the object before it is measured, with the act of measurement. — Wayfarer

If you look at Jim Baggott's categorization of wavefunction anti-realism versus realism at 26:40, he notes that psi does not collapse at all on an anti-realist view (which includes Copenhagen). At 55:00 he categorizes both physical collapse theories (GRW, etc.) and consciousness-causes-collapse (von Neumann–Wigner interpretation) on the realist side. Which is to say, collapse (when the wavefunction is real) is a physical process - whether triggered by matter or mind.

Conversely on an anti-realist view, the wavefunction is a book-keeping device that is useful for making predictions but not for revealing nature. As Baggott quotes Bohr at 29:30, "It is wrong to think that the task of physics is to find out how nature is." It is just the book-keeping device that is adjusted ("collapses") when an observation is made - but there is no physical collapse implied.

How would an anti realist explain why the particle acts differently when collapsed vs uncollapsed? In the double slit experiment for example.

If all it was was a book keeping device for our own sakes, then you’d expect the electrons to act the same way collapsed or uncollapsed no?

That the Copenhagen interpretation is anti realist is news to me. I’m curious where you got that?

Because after all, the matter already exists. — khaled

What 'matter'? That's the problem! What is measured appears as waves or as particles. But, you're saying, behind what is measured there is 'the matter that already exists'. But that is the point at issue! What is being measured? We can't say what is 'behind' the measurement. One set-up produces a wave pattern, the other a particle pattern. Is it really waves or is it really particles? You can't say! That's the paradox, the whole issue in a nutshell.

If that’s the case how come there are direct physical consequences to both, over what we can just say. For example, if you do the double slit experiment on a screen that begins to burn when hit by enough electrons, the screen would burn in whichever pattern is produced, either 2 stripe or interference pattern. There is a real consequence here. We can check the screen after to find out which pattern “really happened” more than just which pattern “we can say happened” — khaled

The results happen, but we can't say that the real cause is a wave or a particle. We can't say that they are attributes of some underlying neither-wave-nor-particle stuff. The answer you get depends on the question you ask, and you're severely limited in infering what is the case beyond that - or rather, there's nothing in physics which will provide you with a warrant for that kind of speculation.

Maybe I’m talking out of my ass — khaled

I think I can safely say that nobody understands quantum mechanics. — Richard Feynmann

How would an anti realist explain why the particle acts differently when collapsed vs uncollapsed? — khaled

That there isn't 'a particle'. You're observing different results, but they're not 'of' something that acts in a certain way.

As Baggott quotes Bohr at 29:30, "It is wrong to think that the task of physics is to find out how nature is." It is just the book-keeping device that is adjusted ("collapses") when an observation is made - but there is no physical collapse implied. — Andrew M

Right! I think that's what I was getting at, but it's been a while since I listened to the whole presentation, so thanks for the reminder.

How would an anti realist explain why the particle acts differently when collapsed vs uncollapsed? In the double slit experiment for example. — khaled

They wouldn't explain why.

Bohr: "It is wrong to think that the task of physics is to find out how nature is."

Heisenberg, "We have to remember that what we observe is not nature herself, but nature exposed to our method of questioning."

If all it was was a book keeping device for our own sakes, then you’d expect the electrons to act the same way collapsed or uncollapsed no? — khaled

At least on Copenhagen, you can only ask about what you observe, not how reality is. There is no unifying picture, just a wave picture or a particle picture depending on the measurement context (complementarity).

Bohr: "We must be clear that when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections."

Heisenberg: "for visualisation, however, we must content ourselves with two incomplete analogies - the wave picture and the corpuscular picture."

That the Copenhagen interpretation is anti realist is news to me. I’m curious where you got that? — khaled

See the OP video at 55:00 - Copenhagen is on the anti-realist side. Note that it's anti-realist about the wavefunction. Reality itself is not denied, but is beyond our ken.

Reality itself is not denied, but is beyond our ken. — Andrew M

This is where I see a parallel with Kant - the distinction between reality as it appears to us and as it is in itself. That's why I posted the Michel Bitbol video on Bohr and Kant. Bitbol is an interesting philosopher of science - I learned of him on this forum. His Academia profile is at https://ens.academia.edu/MichelBitbol

“Really exist in some physical definite state” = collapse. — khaled

But how do we know this? We observe the world and see a definite state?

How do we know we've observed the world to see a definite state? We become conscious of the observation.

If we just had the wave function we can have as many particles as we like, and nothing in the math of the wave function "forces" us to collapse our possible states to more definite states.

The reason viewing the reality as "just the wave function" is that it conflicts with our being conscious of definite states.

Correct. And MWI is the idea that this is what happens, for each possible universe. Again, you have each possible single path block, not a single multi path block (though that’s what you get if you were to superimpose all the blocks on each other) — khaled

You do not understand my point.

There is nothing in quantum mechanics that prevents setting up a wave function state of however many things you want, and simply propagating it forward in time to the end of the universe.

There's nothing preventing a "spacial" view of time in such a mathematical structure so everything is "one block" and all the particles represented by all their possible world lines and spacially representing the probability density of each world line, and having one block.

What's "wrong" with such a view of the universe? (And whether the block-universe we're considering we define as Newtonian, General Relativity or Quantum terms )

The problem is the supposition that there are conscious beings that experience the flow of time. The idea the universe, however it is mathematically described, is one "single block" with past, present and future coexisting (just as up and down direction co-exist) is that it conflicts with the idea of conscious beings inhabiting the universe and experiencing time, and we get that idea from being conscious ourselves.

The point is that it is an analogous problem of a perfectly "fine" interpretation of a mathematical structure of which the only problem is the supposition of conscious beings experiencing time and change (rather than experiencing no time and no change as something existing as a solid changeless block would suggest).

Likewise, that wave functions just propagate indefinitely and never collapse is a perfectly "fine" interpretation of the mathematics of the wave function, of which the only problem is the supposition of conscious beings experiencing definite states represented by real numbers and not these probability distributions represented by complex numbers.

In both cases, since consciousness is "the problem" that prevents, it is entirely reasonable to consider some special relationship between consciousness and these things.

So a single path, for every possible path a world. — khaled

Again, you do not understand my point nor the mathematics of quantum mechanics.

It is not the case that when the wave functions "collapses" that a particle is then considered to have taken a definite path, only the properties observed become more definite for the time of observation, but it is still the case that the particle in some way (we really don't understand) when through all possible paths to get to that observation point: which is why interference patterns emerge (the particle went through, in some sense, both slits and then interfered with itself).

No the point is this isn’t the “result” of the experiment. The variable we want to examine is whether or not the wave function can collapse without our conscious interference. If we get a cookie, where was the conscious interference? We definitely didn’t measure which slit the electron went through. And we didn’t interpret the results on the screen. All that was done by things that aren’t conscious. Yet in the end, when we look at the cookie dispenser, it won’t be “in a superposition of dispensing and not dispensing a cookie” it will either dispense or not dispense a cookie. Based on that we can know whether or not collapse happened without measuring which slit the electrons are going through. That’s the point. Same with the cat. All you’d need is a cookie dispenser there too to know specifically whether or not the cat is alive without observing the cat, just the dispenser.

And, again, address the historical argument: — khaled

Wave function collapse is not a variable.

Variables are states of particles or fields that we can observe. "Wave function collapse" is simply what the "other possibilities" going away is referred to.

For instance, you can have a "probability wave" of a particle in classical mechanics, such as a random walk of a particle Brownian motion or someone who fell of a boat and is adrift at sea. Take the person at sea, based on known constraints, relevant laws of physics etc, a probability distribution of where we are likely to find the person after some time t can be calculated. "Our probability wave" representing where the person might be is the exact same sense of probability as where we might find a particle in a quantum mechanics experiment.

We then go and find the person, and the "wave function" or where they could have been "collapses" in our model because we have new information. This the exact same process as quantum physicists doing measurements and "collapsing" other possibilities that didn't happen when they find one possibility that did happen, they update the model with new information and continue. For instance, finding the persons boot (or what is evaluated as 50% likely to be the persons boot) would update the "lost at sea" model based on this new constraint of observing a boot at location x,y.z at time t.

The difference between classical and quantum probability "wave collapse", is that classical probabilities of the above scenario act only as a one sort of "blobbty diffusion" wave and don't have tell-tale characteristics we'd associate with classic waves such as waves in water.

Critically, as the classical "probability wave / blob" diffuses in space, it always remains cohesive. The probability wave representing where a person maybe based on some initial condition, has no disconnected regions. A person might fall down an elevator shaft, and so is very "unlikely" we'd observe the person in the state of falling down the elevator shaft, but it's not zero probability; we could open one of the other elevator doors on the way down and see the person falling. It's more likely we'd observe the person either just sitting somewhere at the top or then just lying t the bottom of the shaft, than it is to go and observe happen to open an elevator door in the middle and see the falling state, but obviously not impossible.

The classical probability blobs diffuse through space, but never disconnect entirely.

Likewise, someone in a house maybe more probable to be observed in one room or another and less likely we'd observe them right at the moment of going through a door, but obviously we might and people do need to walk through doors to be in different rooms.

We do not believe someone lost at sea somehow "really exists" in all the places we might find them, it is just a mathematical description of probabilities to help us find them. Likewise, we do not believe someone is in "all the rooms" they could be at once, it's just a mathematical description of where we might find them.

Critical to this view that someone lost at sea is a definite state or someone in a house is in a definite state, before we go and check where they actually are, is the probability regions never disconnect (there is a continuous connection of everywhere "they might be", just different probabilities for each place, and we might really find them anywhere in this region; we can run experiments to find that 1/10000 chance of randomly opening the elevator shaft over some time span at the moment someone, let's hope a dummy, is falling).

In quantum mechanics, regions of probability states can be entirely disconnected, and this completely breaks our normal intuition of probability diffusion of "little ball particle" at definite positions through space at each moment in time. How does the electron exist in a definite state but "move" between disconnected regions A and B without any possibility of us finding the electron in some connected bridge state between A and B (i.e. in the doorway)? Likewise, how does an electron interfere with itself so that it's probability of hitting certain regions of a detector is zero, and that even one at a time, electrons produce interference patterns?

The only way to make sense of this is to say the electron does not "move" in a classical sense between A and B and when we look we find where it "really is" but rather the electron somehow co-exists in some sense in both regions, but when we look to find the electron in region A, then somehow it's "existence" in region B disappears. This is what happens mathematically, and "collapsing the wave of probabilities" to the new reality, is a sensical way to describe the mathematical process of updating a model with new information (just as with updating a model of someone lost at sea with information about their probable shoe or then finding the person themselves).

What we cannot easily make sense of is what sort of "substance" the electron (or quantum fields if you prefer) really is to have these characteristics, nor can we easily make sense of how our observations affect the situation (to resolve such questions, we need to make observations, but obviously that is no longer the same question).

Again, address this: Consciousness evolved yes? In order for that to happen we needed to have collapsed, well defined molecules at least yes? And eventually after enough time a conscious thing evolved from these molecules yes?

Then how can consciousness be a requirement for wave function collapse? If it was, it would’ve never evolved. — khaled

The consciousness relation to wave collapse can solve this in different ways; such as simply stating first wave collapsing at some threshold of consciousness or something along those lines (evolution happens in every possibility, and then collapses to the first possibility of consciousness; explaining why there's more matter than antimatter, as only in these probability edge cases does matter outnumber anti-matter, and stars and evolution can happen etc.); but we have no experiment that even shows what is and isn't conscious so this is pseudoscience speculation; not anyway to go back and "observe" the universe before it collapsed to a definite state due to the first observation.

What we do know (or what I know) is that I'm conscious and observe a definite state of the universe around me (certainly more definite than observing "all possibilities" simultaneously). I can know what I observe; I cannot "know" what existence is "really like" prior to my observations. I can note that quantum mechanics basically prevents any intuitive visualizations of what "things are really like at all", but, as a Kantian, it's not really surprising that whatever we can say of the "noumena" always remains fundamentally speculative anyways (maybe new physical theories will lend themselves back to a more "Newtonian" view just to be overturned once again by something even more bizarre than quantum mechanics).

Again, you do not understand my point nor the mathematics of quantum mechanics. — boethius

I appreciate the long explanation but there is nothing there I didn’t already know. Maybe it’s you who doesn’t understand my point?

The only way to make sense of this is to say the electron does not "move" in a classical sense between A and B and when we look we find where it "really is" but rather the electron somehow co-exists in some sense in both regions, but when we look to find the electron in region A, then somehow it's "existence" in region B disappears. — boethius

Ok. Agreed so far.

This is what happens mathematically, and "collapsing the wave of probabilities" to the new reality, is a sensical way to describe the mathematical process of updating a model with new information — boethius

But it’s not just “updating the model with new information” is it? It’s changing how the particle behaves. When we collapse the wave of probabilities, suddenly the particle behaves differently than before we did. That’s the key difference between probability distributions of quantum mechanics and other fields.

The probability distribution of the person at sea is “epistemic”. There is definitely a person at sea, we know everything about him except where he is, and so we make a model to find the most likely locations he can be at.

The probability distribution of an electron is “ontological”. It’s not that there is a definite electron whose location we don’t know. If that were the case, you’d always see 2 stripe pattern. No, the electron truly behaves differently according to whether or not it has collapsed. It is truly “everywhere at once” until measured

such as simply stating first wave collapsing at some threshold of consciousness or something along those lines — boethius

Yes but how will we ever reach that threshold if consciousness was what causes wave function collapse?

To be conscious you need a brain. And for a brain you need collapsed, well defined atoms and electrons. So in order to get consciousness you need collapse to have already occurred. So consciousness can’t be the only thing capable of causing collapse.

Unless you think that somehow collapse can happen “back in time”? But you also said:

It is not the case that when the wave functions "collapses" that a particle is then considered to have taken a definite path — boethius

You seem to be suggesting that the world went through all possible paths, until consciousness was reached in one of the paths, then somehow the awesome power of consciousness ontologically corrected history so that everything went through that one path only.

evolution happens in every possibility, and then collapses to the first possibility of consciousness — boethius

You need planets, suns and water at least for evolution to occur. You can’t get those things without collapse. Those things need to exist definitively for evolution to occur, without anyone looking at them. So again, you wouldn’t get consciousness. Ever. You’d get quantum soup awaiting collapse by consciousness, which will never happen because consciousness needs brains not quantum soup.

but, as a Kantian, it's not really surprising that whatever we can say of the "noumena" always remains fundamentally speculative anyways — boethius

I don’t mind that.

What I do mind is the suggestion that consciousness affects noumena.