That depends on what you mean by “settle”. The only thing that you can definitively say is that the transition between the quantum and the classical is gradual, not abrupt. Because of this, any statement about a classical world is necessarily an approximation of some sort, and all approximations break down if you lean on them in the right way. Copenhagen breaks down most easily because it only applies under some very particular circumstances. Those circumstances happen to be very common, which is why Copenhagen is not completely useless, but nowadays it is common to do experiments under which the Copenhagen approximation conditions do not apply. Multiple-worlds is mathematically tenable, but it has some very serious problems as an explanatory theory and it makes predictions that even its adherents seem unwilling to accept.
Personally, I find the rhetoric of QIT/relational-QM/Ithaca to be far less taxing on my intuition than multiple-worlds. These interpretations acknowledge that classical reality is a slice of the wave function, that there are many different ways to slice up the wave function to obtain a classical reality, and therefore there are many potential classical realities. But there is one classical reality that is privileged to me because it happens to be the one that I’m living in, which is to say, it’s the reality that is mutually entangled (and therefore classically correlated) with the massively-mutually-entangled system that is me. In an absolute sense I am no more or less real than all the other potential mes that you get by slicing up the wave function in different ways, but I don’t care about that except in the abstract. Day-to-day, what matters to me—this me, the one that is writing these words—is what is correlated with (this) me.
The cool thing about this is that if you are reading these words—the ones written by this me—then you are entangled with me and therefore classically correlated with me and therefore we are both emerging from the same slice of the wave function, and so the exact same argument applies to you: both of us can proceed on the assumption that our classical reality is the One True Classical Reality even though we can both understand in the abstract that this isn’t really true, and that by doing the right kinds of quantum experiments we can actually demonstrate to ourselves that it isn’t really true. For me personally, that makes QIT the best approximation to use because it’s the one that applies in the greatest variety of circumstances and has the fewest conceptual problems. But it’s ultimately a matter of personal preference.
Multiple-worlds is mathematically tenable, but it has some very serious problems as an explanatory theory and it makes predictions that even its adherents seem unwilling to accept.
Doesn’t the QIT you describe make the exact same predictions, also the Russian roulette you mentioned?
But there is one classical reality that is privileged to me because it happens to be the one that I’m living in, which is to say, it’s the reality that is mutually entangled (and therefore classically correlated) with the massively-mutually-entangled system that is me. In an absolute sense I am no more or less real than all the other potential mes that you get by slicing up the wave function in different ways, but I don’t care about that except in the abstract.
But there’s no single privileged future you, right?
Doesn’t the QIT you describe make the exact same predictions, also the Russian roulette you mentioned?
Nope.
But there’s no single privileged future you, right?
There is no single privileged future me now, but when my future becomes my present there will be. (Also, see note below.)
You can actually do this experiment: listen to a geiger counter, or tune an old-school TV to an inactive channel and watch the snow on the screen. The math says that during this process there are an inconceivably vast number of you’s being split off every time the geiger counter clicks (or fails to click) or every time you perceive a light or dark pixel on the screen. But you will only ever experience being one of those you’s. Yes, all those other you’s do exist, but the you that you perceive yourself to be can never interact with any of them, so they may as well not exist for the one you that you perceive yourself to be. And so the one you that you perceive yourself to be may as well live your life as if all those other you’s didn’t exist even though they really do.
(NOTE: there is really no such thing as “now”, and you don’t even have to go quantum to see that. Simultaneity gets tossed out the window with special relativity. There is my “now” and there is your “now” and they will not, in general, be the same.)
I found your paper easy to follow and maybe insightful (I’ll have to read it more carefully the second time) but like qmotus, I don’t understand your reasoning in this thread. I’m assuming MWI is just an interpretation of unitary QM, so makes all the same mathematical predictions as other non-collapse theories. And the roulette story is just one way of looking at it, from the perspective of what I consider my (classical) self and what I call the future.
Since you are not claiming that QIT makes different mathematical predictions than MWI, how can you claim they make different predictions at all?
QIT and MWI don’t make any different predictions that are testable in a single classical universe (obviously, because QIT and MWI are just different interpretation of QM, so they both make the same predictions for all observables, namely, the predictions made by QM).
QIT and MWI are simply differences in perspective—the God’s eye view (MWI) versus the mortal’s-eye-view (QIT). Neither view is “correct”, but since I (the thing engaged in this conversation) am a mortal, I choose the mortal’s-eye-view as more relevant for day-to-day decision making. But as I keep saying, it’s ultimately a matter of personal preference.
The problem with quantum roulette is that it takes a prediction made from a God’s-eye-view and tries to apply it in a mortal’s-eye-view context. Yes, God will be able to see that there is a you that survived the process and went on to live the life of Riley. But whether or not you will be able to see that is a very open question. (God will also be able to see a lot of branches of the multiverse containing your friends and loved ones mourning your untimely death.)
Note that playing quantum roulette successfully depends crucially on the speed with which you can kill yourself. Trying to play by slitting your wrists, for example, doesn’t work because once you see that your wrists are slit you can’t roll that back. So the success of the enterprise depends entirely on killing yourself fast enough that you don’t become aware of your imminent and (in the relevant branches of the multiverse) unavoidable death. How fast is fast enough? Well, that is (literally!) the sixty-four-million-dollar question. Unless you have an answer that you are very confident is the correct one, it seems to me like an imprudent risk to take.
(This comment is a reply to another branch of this discussion as well.)
Yes, God will be able to see that there is a you that survived the process and went on to live the life of Riley. But whether or not you will be able to see that is a very open question
I disagree. To keep things simple, let’s suppose that the bullet, if it hits, really will kill the participant with practically 100% certainty and will do so practically immediately (I’ll come to this a bit later). In that case the only outcome the participant can expect to experience, and that they will experience with certainty, is that the gun didn’t fire. This is exactly what happens if you take the mortal’s-eye-view; God, as you mentioned, will notice that elsewhere in the multiverse, the participant did get hit. Now, whether the participant cares about their loved ones or the copies that die in the attempt is a matter of preferences, but if we’re simply talking about which outcome to experience, this is how it goes, I think.
Note that playing quantum roulette successfully depends crucially on the speed with which you can kill yourself. Trying to play by slitting your wrists, for example, doesn’t work because once you see that your wrists are slit you can’t roll that back. So the success of the enterprise depends entirely on killing yourself fast enough that you don’t become aware of your imminent and (in the relevant branches of the multiverse) unavoidable death. How fast is fast enough? Well, that is (literally!) the sixty-four-million-dollar question. Unless you have an answer that you are very confident is the correct one, it seems to me like an imprudent risk to take.
With this I agree, which is why I think the quantum Russian roulette or quantum suicide scenarios are mostly interesting as a thought experiment, as they’re intended to be. But there are practical situations that are somewhat analogous: think, for example, about a terminally ill patient who faces an almost certain death within several days. Should they expect to survive or continue to experience things, and if so, in what way? My understanding is that according to quantum mechanics, there are all kinds of weird scenarios with non-zero probability that make “survival” possible, such as simply surviving one more day indefinitely despite all odds, being miraculously cured, or maybe being resurrected by a hyper-advanced future civilization in a simulation. Note that, in principle, this probably applies to any possible life-and-death situation.
I used the word “experience” a number of times there, which brings me to a point you made in another comment:
Notice (!) that when you start to talk about “noticing” things you are tacitly bringing consciousness into the discussion, which is a whole ‘nuther can o’ philosophical worms.
I don’t think this can of worms is that bad. We have a pretty good grasp of what it means to be conscious, even if we can’t define it exactly; and also we’re (at least I am) pretty confident that it’s a purely physical phenomenon with nothing supernatural and thus subject to the laws of QM. I think that’s enough. Where it does get a bit problematic is when we’re talking about scenarios like the one with the terminally ill patient; presumably there’s also a possibility that the patient’s consciousness degrades until it no longer makes sense to call them conscious, since there’s probably no clear line anywhere separating conscious and non-conscious in this way. (This might also imply that if we should expect to die, we should expect to do so by very slow decay, like patients with Alzheimer’s, which doesn’t sound too good to me.)
I agree with most of what you say. Consciousness is not supernatural. But it is still problematic because:
the only outcome the participant can expect to experience, and that they will experience with certainty
“Only outcome you can experience” is not quite the same thing as “Will experience with certainty.” Let’s go back to the case where you survive in both branches. The outcome you do experience is the only outcome that you can experience. The trick is that this is really two statements disguised as one. After the event there are two you’s, you1 and you2. The outcome that you1 do experience is the only outcome you1 can experience, and the outcome you2 do experience is the only outcome you2 can experience. This remains true (I believe) even if one of those experiences is the null experience of having your consciousness enter the cosmic void.
Reasonable people could disagree, I suppose. We can never know what the null experience “feels like” because by definition it doesn’t feel like anything. Personally, I find even the possibility that this argument could be correct to be sufficient reason for me to avoid playing quantum roulette. But everyone needs to choose their own risk posture.
It was two statements: “only outcome the participant can expect to experience” because I think that no, it is not possible to experience a null experience; and “will experience with certainty” because I believe quantum mechanics, when interpreted literally, means that the experience will exist.
As I said, I don’t find the Russian roulette a particularly interesting scenario in reality, nor something that I would like to try myself; it’s because I think this applies to other life-and-death situations as well that I think the basic question is important.
In that case the only outcome the participant can expect to experience, and that they will experience with certainty, is that the gun didn’t fire
Yes, that’s the point. Every future version of you will of course call themselves “you”.
Note that playing quantum roulette successfully depends crucially on the speed with which you can kill yourself.
With this I agree, which is why I think the quantum Russian roulette or quantum suicide scenarios are mostly interesting as a thought experiment, as they’re intended to be.
Although I don’t want to advocate performing the roulette experiment, I do disagree. If it’s a quantum certainty that all future branches of you die off, perhaps due to a conservation law, then only those versions of you which didn’t go down that branch will be conscious.
Even if it isn’t certain, because it seems like we are more likely to experience the branches that match our classical explanations in the following scenario after a few minutes I would expect to be version 3. Version 1 is of course impossible and only with a very short-sighted definition of self do I need to consider version 2.
Yeah. I meant that I don’t find the roulette scenario very relevant since I believe that we’re much more likely to experience some other scenario where this property of the quantum multiverse becomes relevant, like the terminal illness one I described. Most of us won’t play the roulette.
Anyways, there’s a flaw in lisper’s original argument: death is not unavoidable even after wrists have been slit.
Oh, come on. Surely you do not dispute that there are ways of dying that are both unavoidable and non-instantaneous. What difference does it make what the details are?
If I decide to open my wrists, there are many ways that I can still keep going: I may simply faint and wake up in a hospital, the paramedics having arrived just in time despite all odds; quantum fluctuations may spawn a hitherto unkown angelic being who heals me; or a highly advanced future civilization may decide to run an afterlife simulation for 21st century earthlings that I end up in. As far as I know, these are all scenarios with a non-zero probability according to quantum mechanics and that this is in principle generalizable to any other life-and-death situation, although I have to admit that my understanding of QM is somewhat fuzzy. Feel free to correct me.
quantum fluctuations may spawn a hitherto unkown angelic being who heals me
Quantum fluctuations may also spawn the ghost of Karl Popper who will wag his finger at you and remind you that unfalsifiable statements aren’t terribly useful.
That said, I do believe that what I said is true if we assume that quantum mechanics is a complete theory, and pretty much all evidence so far points towards it. It’s a fairly common idea among physicists nowadays, actually, that not every single prediction needs to be falsifiable. David Deutsch has also mentioned that most fiction or something arbitrarily close to it is probably real in some part of the quantum multiverse.
Once you start to invoke “hitherto unknown angelic beings” and give up on falsifiablity you are basically in a religious dispute and I don’t see much advantages to this new religion over the existing traditional ones.
The point was to illustrate that there can be ways to survive a seemingly inevitably fatal situation that are extremely unlikely but still have a non-zero probability of occurring and that, therefore, will happen in some Everett branches (assuming MWI is true). Being rescued by an angel is probably one of the least likely ways for somebody to survive after slicing their wrists, so I would bet on simply waking up in a hospital instead.
I don’t think claims like that need to be empirically falsified. Quantum mechanics is falsifiable, and so far it’s withstood every test. I suppose you could try to prove that survival probability in some case or in some way is zero by math alone, but I don’t think that’s true.
Well, from my point of view an unfalsifiable illustration doesn’t really illustrate anything. “There could be a god and she could save me” is a fully generic answer to absolutely anything.
You can just ignore the angelic being thing if it bothers you too much. Even so, I’d argue that at least in almost every slit-wrists scenario, there is a non-zero probability of being rescued by modern medicine. But do not that I’m not saying that the angelic being will in fact appear somewhere! That one would follow from quantum mechanics being a complete theory and MWI (or QIT) being a correct interpretation, both of which are surely debatable (and even then it would only happen in a very small minority of all worlds).
I wonder where you would draw the line with falsifiability though. For example, according to quantum mechanics there is a non-zero probability (and this one I’m quite certain about) that when you perform a double-slit experiment, all the photons will hit the detector in just the right way to give results that agree with the world being classical. Is this claim falsifiable? I guess not, but it’s still true.
So, replace slit wrists with standing in the center of Hiroshima on August 6, 1945 around 8:15 looking up at the sky.
All right, that’s more difficult. So are you sure that there’s no way, miraculous or non-miraculous, to keep existing in that situation?
In your example it is possible to observe the classical result from the double-slit experiment, so I don’t know why you think it’s not falsifiable.
You would have to run the experiment very many times to see the classical result even once. In practice it’s not possible to test it. And what if my claim is not true—how would you show that?
Your default assumption regarding the classical result in a double-slit experiment seems to be that it is actually allowed by the formalism of quantum mechanics. So why does your default assumption seems to be that the formalism of quantum mechanics says that the angel thing is impossible?
So are you sure that there’s no way, miraculous or non-miraculous, to keep existing in that situation?
Divine intervention can solve ALL problems.
So why does your default assumption seems to be that the formalism of quantum mechanics says that the angel thing is impossible?
That is not my assumption and QM says nothing about angelic beings. My problem is that deux ex machina, in the form of an angel or not, is the answer to absolutely everything and so is useless.
As to why the “angel thing” is unlikely, let me introduce you to Bertrand Russel. You see, he had a teapot...
That is not my assumption and QM says nothing about angelic beings. My problem is that deux ex machina, in the form of an angel or not, is the answer to absolutely everything and so is useless.
Maybe you misunderstand my point. I’m not proposing the angel thing as an answer to anything. I’d rather say that I’m trying to present a problem, actually.
Unfortunately, I don’t understand the math of QM enough to make a convincing argument here. But basically my logic is this: the probability that instead of an angel, a disembodied brain will materialize in front of me is apparently non-zero according to our current knowledge, since the Boltzmann brain paradox is something that is taken seriously by physicists. I don’t see any fundamental difference between this and a blonde guy dressed in white with wings (perhaps made of cardboard) who’s very skilled at treating slit wrists materializing instead, so I assume that also has a small but non-zero probability. (Also, the probability that I would survive a nuclear explosion by tunneling to a safe distance is non-zero, I believe, by the same logic that the probability of me tunneling to the room next door is non-zero, which I’ve also heard physicists say.)
Now, the possible existence of Boltzmann brains is actually generally considered a problem, but scientists who work on that problem, as far as I know, usually don’t deny that our current understanding of physics says that Boltzmann brains are a real thing; instead, they think that it either shows a flaw in the theories that predict them, or that our understanding of those theories is incomplete in some way (Sean Carroll has written about this). I don’t know, but I suppose it’s also possible that the world simply really is a weird place.
basically my logic is this: the probability that instead of an angel, a disembodied brain will materialize in front of me is apparently non-zero according to our current knowledge
You are basically arguing that “the probability of X is non-zero for all X”. That is true (or unfalsifiable) in the same sense that solipsism is true (or unfalsifiable). No one can prove to you that it ain’t so, but it’s an entirely uninteresting and useless position to hold.
It’s not non-zero for all X. If I claim that “according to QM, there’s a non-zero probability two entangled particles have the same spin”, one could just produce the math necessary to show that this claim is false. Likewise, if my claim about QM saying that the probability of an angel appearing is non-zero, I’m sure it’s possible to do that (it might be difficult, though). The same with those Boltzmann brains, but physicists seem to think that their probability really is non-zero. Solipsism, on the other hand, is completely immune to such attacks.
The important thing here is really whether what I’m claiming follows from the math of quantum mechanics or not. Physicists don’t try to falsify every single prediction that quantum mechanics makes, because they already think there’s enough evidence (well, most do) that the theory is correct. There obviously is no such evidence for solipsism.
The probability of our current understanding of QM to be false is non-zero, too.
Things that QM forbids might be allowed by the next theory that follows it (what does Newtonian physics say about quantum tunneling? Absolutely impossible.)
You are granting QM the status of absolute, final truth and I see no reason for that. There is non-zero probability that it is mistaken :-P
I tried to be careful about this. In an earlier post, I said: “But do not that I’m not saying that the angelic being will in fact appear somewhere! That one would follow from quantum mechanics being a complete theory and MWI (or QIT) being a correct interpretation, both of which are surely debatable (and even then it would only happen in a very small minority of all worlds).”
That said, I think it’s quite a radical position to assign much probability to the possibility that QM is wrong. So far it’s consistent with all the evidence that we have, and there’s no evidence to support any of the competing theories or modifications, like objective-collapse theories. Because of this, a hypothetical improved theory might also contain all the weird stuff that QM does, plus some more.
On the other hand, I sometimes wonder if the people working on these theories would be more inclined to question them if they thought more about all the absurd implications they potentially have. (They might not: I recall reading a statement somewhere by Steven Weinberg who thought that eternal inflation or some other multiverse-predicting theory is a miserable theory, but the best that there is and possibly correct.)
I think it’s quite a radical position to assign much probability to the possibility that QM is wrong.
I don’t think so, with the slight change from “QM is wrong” to “QM is limited in its applicability, just like Newtonian physics”.
But in any case, in this thread you operate in a black-and-white world of “zero probability” and “non-zero probability”. I am pointing out that the set of zero-probability events is empty.
I don’t think so, with the slight change from “QM is wrong” to “QM is limited in its applicability, just like Newtonian physics”.
Fair enough. I suppose one could say that the problems with combining QM and general relativity suggest that QM needs to be modified, but so far we don’t have experimental evidence for anything but pure QM, I believe.
But in any case, in this thread you operate in a black-and-white world of “zero probability” and “non-zero probability”. I am pointing out that the set of zero-probability events is empty.
Well, our discussion spun off from a comment where lisper claimed that surely there are situations where death is inevitable. I countered by saying that as far as I know, there’s always some way to survive that has a non-zero probability according to quantum mechanics, so that’s where the emphasis on zero vs non-zero probability originally came. Note that the view advocated in the original post views the formalism of quantum mechanics as an accurate description at all scales and also says that all events with a non-zero probability will happen (but that the ones we end up not observing are not something we should care about).
I think we agree but I was trying to make a bigger point than your reply captures. I doubt that you will even experience the terminal illness assuming there are many more possible futures where you stay healthy and anti-aging science advances than ones where you are miraculously saved at the last minute, by aliens or luck.
That makes the roulette scenario relevant to our experience. Because if you have the conviction to pull the trigger if something doesn’t go your way you have the three options I laid out. So most likely you don’t even have to try—assuming you are sure you will.
Well, I’d rather say that I will perceive being every one of them; it’s just that no future me will perceive being more than one of the future mes. The terminology gets quite confusing here, but I think the Quantum Russian Roulette you mentioned (and quantum suicide and immortality, by extension, for example) is one situation where this aspect of quantum theory becomes somewhat apparent, which is why I think it would be interesting if you elaborated a bit more on how you think the predictions QTI and MWI make differ from each other.
It depends on what you mean by “I”. This is the crux of the matter. MWI takes a God’s-eye perspective and looks at the whole wave function. On that view, there are many you’s (i.e. many slices of the wave function that contain macroscopic systems of mutually entangled particles that perceive themselves to be you).
QIT takes the perspective of the-you-that-you-currently-perceive-yourself-to-be. You will only ever perceive one of that kind of you.
For the purposes of making decisions it makes more sense to take the latter perspective because it’s the-latter-kind-of-you that is making the decisions and has to live with the consequences.
I would say that a major difference between MWI and various collapse interpretations is that there are situations where according to collapse interpretations there most likely will be no future you; but according to MWI there surely will, although their amplitude is low (the aforementioned Russian roulette is one such situation, for instance). I find it somewhat difficult to think about those from the perspective you advocate.
No. Not “will”. IS. If you’re going to take the God’s eye view then you have to let go of your intuitions about time along with your intuitions about classical reality. The wave function is a static four-dimensional thing. Time emerges from the wave function in exactly the same way that classical reality does. You have to be careful not to apply terminology from the mortal’s-eye-view to the God’s-eye-view. That’s how you get yourself into trouble.
UPDATE: Here is a popular article about how time emerges from entanglement.
I think what I said applies when you take a first-person point of view. If you’re a participant in a quantum suicide experiment, then if you expect a collapse interpretation to be an accurate description of reality, you should expect to eventually be hit by a bullet and die. But both MWI and QIT predict that you will continuously notice that the gun doesn’t fire. The difference is not in the point of view taken, it’s in the fact that the parts of the wavefunction that contain a (from first-person eye-view) future version of the participant actually are there.
But both MWI and QIT predict that you will continuously notice that the gun doesn’t fire.
No, that’s not quite true. QIT predicts that if you notice anything then you will notice that the gun didn’t fire. But QIT does not guarantee that you will notice anything. You could just die.
Notice (!) that when you start to talk about “noticing” things you are tacitly bringing consciousness into the discussion, which is a whole ‘nuther can o’ philosophical worms.
How far does it go in solving the measurement problem? Can you derive the Born rule? Can you settle the single/many world dichotomy?
Yes.
That depends on what you mean by “settle”. The only thing that you can definitively say is that the transition between the quantum and the classical is gradual, not abrupt. Because of this, any statement about a classical world is necessarily an approximation of some sort, and all approximations break down if you lean on them in the right way. Copenhagen breaks down most easily because it only applies under some very particular circumstances. Those circumstances happen to be very common, which is why Copenhagen is not completely useless, but nowadays it is common to do experiments under which the Copenhagen approximation conditions do not apply. Multiple-worlds is mathematically tenable, but it has some very serious problems as an explanatory theory and it makes predictions that even its adherents seem unwilling to accept.
Personally, I find the rhetoric of QIT/relational-QM/Ithaca to be far less taxing on my intuition than multiple-worlds. These interpretations acknowledge that classical reality is a slice of the wave function, that there are many different ways to slice up the wave function to obtain a classical reality, and therefore there are many potential classical realities. But there is one classical reality that is privileged to me because it happens to be the one that I’m living in, which is to say, it’s the reality that is mutually entangled (and therefore classically correlated) with the massively-mutually-entangled system that is me. In an absolute sense I am no more or less real than all the other potential mes that you get by slicing up the wave function in different ways, but I don’t care about that except in the abstract. Day-to-day, what matters to me—this me, the one that is writing these words—is what is correlated with (this) me.
The cool thing about this is that if you are reading these words—the ones written by this me—then you are entangled with me and therefore classically correlated with me and therefore we are both emerging from the same slice of the wave function, and so the exact same argument applies to you: both of us can proceed on the assumption that our classical reality is the One True Classical Reality even though we can both understand in the abstract that this isn’t really true, and that by doing the right kinds of quantum experiments we can actually demonstrate to ourselves that it isn’t really true. For me personally, that makes QIT the best approximation to use because it’s the one that applies in the greatest variety of circumstances and has the fewest conceptual problems. But it’s ultimately a matter of personal preference.
Doesn’t the QIT you describe make the exact same predictions, also the Russian roulette you mentioned?
But there’s no single privileged future you, right?
Nope.
There is no single privileged future me now, but when my future becomes my present there will be. (Also, see note below.)
You can actually do this experiment: listen to a geiger counter, or tune an old-school TV to an inactive channel and watch the snow on the screen. The math says that during this process there are an inconceivably vast number of you’s being split off every time the geiger counter clicks (or fails to click) or every time you perceive a light or dark pixel on the screen. But you will only ever experience being one of those you’s. Yes, all those other you’s do exist, but the you that you perceive yourself to be can never interact with any of them, so they may as well not exist for the one you that you perceive yourself to be. And so the one you that you perceive yourself to be may as well live your life as if all those other you’s didn’t exist even though they really do.
(NOTE: there is really no such thing as “now”, and you don’t even have to go quantum to see that. Simultaneity gets tossed out the window with special relativity. There is my “now” and there is your “now” and they will not, in general, be the same.)
Hi lisper,
I found your paper easy to follow and maybe insightful (I’ll have to read it more carefully the second time) but like qmotus, I don’t understand your reasoning in this thread. I’m assuming MWI is just an interpretation of unitary QM, so makes all the same mathematical predictions as other non-collapse theories. And the roulette story is just one way of looking at it, from the perspective of what I consider my (classical) self and what I call the future.
Since you are not claiming that QIT makes different mathematical predictions than MWI, how can you claim they make different predictions at all?
QIT and MWI don’t make any different predictions that are testable in a single classical universe (obviously, because QIT and MWI are just different interpretation of QM, so they both make the same predictions for all observables, namely, the predictions made by QM).
QIT and MWI are simply differences in perspective—the God’s eye view (MWI) versus the mortal’s-eye-view (QIT). Neither view is “correct”, but since I (the thing engaged in this conversation) am a mortal, I choose the mortal’s-eye-view as more relevant for day-to-day decision making. But as I keep saying, it’s ultimately a matter of personal preference.
The problem with quantum roulette is that it takes a prediction made from a God’s-eye-view and tries to apply it in a mortal’s-eye-view context. Yes, God will be able to see that there is a you that survived the process and went on to live the life of Riley. But whether or not you will be able to see that is a very open question. (God will also be able to see a lot of branches of the multiverse containing your friends and loved ones mourning your untimely death.)
Note that playing quantum roulette successfully depends crucially on the speed with which you can kill yourself. Trying to play by slitting your wrists, for example, doesn’t work because once you see that your wrists are slit you can’t roll that back. So the success of the enterprise depends entirely on killing yourself fast enough that you don’t become aware of your imminent and (in the relevant branches of the multiverse) unavoidable death. How fast is fast enough? Well, that is (literally!) the sixty-four-million-dollar question. Unless you have an answer that you are very confident is the correct one, it seems to me like an imprudent risk to take.
(This comment is a reply to another branch of this discussion as well.)
I disagree. To keep things simple, let’s suppose that the bullet, if it hits, really will kill the participant with practically 100% certainty and will do so practically immediately (I’ll come to this a bit later). In that case the only outcome the participant can expect to experience, and that they will experience with certainty, is that the gun didn’t fire. This is exactly what happens if you take the mortal’s-eye-view; God, as you mentioned, will notice that elsewhere in the multiverse, the participant did get hit. Now, whether the participant cares about their loved ones or the copies that die in the attempt is a matter of preferences, but if we’re simply talking about which outcome to experience, this is how it goes, I think.
With this I agree, which is why I think the quantum Russian roulette or quantum suicide scenarios are mostly interesting as a thought experiment, as they’re intended to be. But there are practical situations that are somewhat analogous: think, for example, about a terminally ill patient who faces an almost certain death within several days. Should they expect to survive or continue to experience things, and if so, in what way? My understanding is that according to quantum mechanics, there are all kinds of weird scenarios with non-zero probability that make “survival” possible, such as simply surviving one more day indefinitely despite all odds, being miraculously cured, or maybe being resurrected by a hyper-advanced future civilization in a simulation. Note that, in principle, this probably applies to any possible life-and-death situation.
I used the word “experience” a number of times there, which brings me to a point you made in another comment:
I don’t think this can of worms is that bad. We have a pretty good grasp of what it means to be conscious, even if we can’t define it exactly; and also we’re (at least I am) pretty confident that it’s a purely physical phenomenon with nothing supernatural and thus subject to the laws of QM. I think that’s enough. Where it does get a bit problematic is when we’re talking about scenarios like the one with the terminally ill patient; presumably there’s also a possibility that the patient’s consciousness degrades until it no longer makes sense to call them conscious, since there’s probably no clear line anywhere separating conscious and non-conscious in this way. (This might also imply that if we should expect to die, we should expect to do so by very slow decay, like patients with Alzheimer’s, which doesn’t sound too good to me.)
I agree with most of what you say. Consciousness is not supernatural. But it is still problematic because:
“Only outcome you can experience” is not quite the same thing as “Will experience with certainty.” Let’s go back to the case where you survive in both branches. The outcome you do experience is the only outcome that you can experience. The trick is that this is really two statements disguised as one. After the event there are two you’s, you1 and you2. The outcome that you1 do experience is the only outcome you1 can experience, and the outcome you2 do experience is the only outcome you2 can experience. This remains true (I believe) even if one of those experiences is the null experience of having your consciousness enter the cosmic void.
Reasonable people could disagree, I suppose. We can never know what the null experience “feels like” because by definition it doesn’t feel like anything. Personally, I find even the possibility that this argument could be correct to be sufficient reason for me to avoid playing quantum roulette. But everyone needs to choose their own risk posture.
It was two statements: “only outcome the participant can expect to experience” because I think that no, it is not possible to experience a null experience; and “will experience with certainty” because I believe quantum mechanics, when interpreted literally, means that the experience will exist.
As I said, I don’t find the Russian roulette a particularly interesting scenario in reality, nor something that I would like to try myself; it’s because I think this applies to other life-and-death situations as well that I think the basic question is important.
Yes, that’s the point. Every future version of you will of course call themselves “you”.
Although I don’t want to advocate performing the roulette experiment, I do disagree. If it’s a quantum certainty that all future branches of you die off, perhaps due to a conservation law, then only those versions of you which didn’t go down that branch will be conscious.
Even if it isn’t certain, because it seems like we are more likely to experience the branches that match our classical explanations in the following scenario after a few minutes I would expect to be version 3. Version 1 is of course impossible and only with a very short-sighted definition of self do I need to consider version 2.
fire the gun and die (0%)
fire the gun and be miraculously saved (1%)
don’t even attempt the experiment (99%)
Yeah. I meant that I don’t find the roulette scenario very relevant since I believe that we’re much more likely to experience some other scenario where this property of the quantum multiverse becomes relevant, like the terminal illness one I described. Most of us won’t play the roulette.
Anyways, there’s a flaw in lisper’s original argument: death is not unavoidable even after wrists have been slit.
Oh, come on. Surely you do not dispute that there are ways of dying that are both unavoidable and non-instantaneous. What difference does it make what the details are?
If I decide to open my wrists, there are many ways that I can still keep going: I may simply faint and wake up in a hospital, the paramedics having arrived just in time despite all odds; quantum fluctuations may spawn a hitherto unkown angelic being who heals me; or a highly advanced future civilization may decide to run an afterlife simulation for 21st century earthlings that I end up in. As far as I know, these are all scenarios with a non-zero probability according to quantum mechanics and that this is in principle generalizable to any other life-and-death situation, although I have to admit that my understanding of QM is somewhat fuzzy. Feel free to correct me.
Quantum fluctuations may also spawn the ghost of Karl Popper who will wag his finger at you and remind you that unfalsifiable statements aren’t terribly useful.
Heh, I would definitely like to see that.
That said, I do believe that what I said is true if we assume that quantum mechanics is a complete theory, and pretty much all evidence so far points towards it. It’s a fairly common idea among physicists nowadays, actually, that not every single prediction needs to be falsifiable. David Deutsch has also mentioned that most fiction or something arbitrarily close to it is probably real in some part of the quantum multiverse.
Once you start to invoke “hitherto unknown angelic beings” and give up on falsifiablity you are basically in a religious dispute and I don’t see much advantages to this new religion over the existing traditional ones.
The point was to illustrate that there can be ways to survive a seemingly inevitably fatal situation that are extremely unlikely but still have a non-zero probability of occurring and that, therefore, will happen in some Everett branches (assuming MWI is true). Being rescued by an angel is probably one of the least likely ways for somebody to survive after slicing their wrists, so I would bet on simply waking up in a hospital instead.
I don’t think claims like that need to be empirically falsified. Quantum mechanics is falsifiable, and so far it’s withstood every test. I suppose you could try to prove that survival probability in some case or in some way is zero by math alone, but I don’t think that’s true.
Well, from my point of view an unfalsifiable illustration doesn’t really illustrate anything. “There could be a god and she could save me” is a fully generic answer to absolutely anything.
You can just ignore the angelic being thing if it bothers you too much. Even so, I’d argue that at least in almost every slit-wrists scenario, there is a non-zero probability of being rescued by modern medicine. But do not that I’m not saying that the angelic being will in fact appear somewhere! That one would follow from quantum mechanics being a complete theory and MWI (or QIT) being a correct interpretation, both of which are surely debatable (and even then it would only happen in a very small minority of all worlds).
I wonder where you would draw the line with falsifiability though. For example, according to quantum mechanics there is a non-zero probability (and this one I’m quite certain about) that when you perform a double-slit experiment, all the photons will hit the detector in just the right way to give results that agree with the world being classical. Is this claim falsifiable? I guess not, but it’s still true.
So, replace slit wrists with standing in the center of Hiroshima on August 6, 1945 around 8:15 looking up at the sky.
In the usual way: is it possible to observe an empirical result which will either prove of disprove the claim in question?
In your example it is possible to observe the classical result from the double-slit experiment, so I don’t know why you think it’s not falsifiable.
All right, that’s more difficult. So are you sure that there’s no way, miraculous or non-miraculous, to keep existing in that situation?
You would have to run the experiment very many times to see the classical result even once. In practice it’s not possible to test it. And what if my claim is not true—how would you show that?
Your default assumption regarding the classical result in a double-slit experiment seems to be that it is actually allowed by the formalism of quantum mechanics. So why does your default assumption seems to be that the formalism of quantum mechanics says that the angel thing is impossible?
Divine intervention can solve ALL problems.
That is not my assumption and QM says nothing about angelic beings. My problem is that deux ex machina, in the form of an angel or not, is the answer to absolutely everything and so is useless.
As to why the “angel thing” is unlikely, let me introduce you to Bertrand Russel. You see, he had a teapot...
Maybe you misunderstand my point. I’m not proposing the angel thing as an answer to anything. I’d rather say that I’m trying to present a problem, actually.
Unfortunately, I don’t understand the math of QM enough to make a convincing argument here. But basically my logic is this: the probability that instead of an angel, a disembodied brain will materialize in front of me is apparently non-zero according to our current knowledge, since the Boltzmann brain paradox is something that is taken seriously by physicists. I don’t see any fundamental difference between this and a blonde guy dressed in white with wings (perhaps made of cardboard) who’s very skilled at treating slit wrists materializing instead, so I assume that also has a small but non-zero probability. (Also, the probability that I would survive a nuclear explosion by tunneling to a safe distance is non-zero, I believe, by the same logic that the probability of me tunneling to the room next door is non-zero, which I’ve also heard physicists say.)
Now, the possible existence of Boltzmann brains is actually generally considered a problem, but scientists who work on that problem, as far as I know, usually don’t deny that our current understanding of physics says that Boltzmann brains are a real thing; instead, they think that it either shows a flaw in the theories that predict them, or that our understanding of those theories is incomplete in some way (Sean Carroll has written about this). I don’t know, but I suppose it’s also possible that the world simply really is a weird place.
You are basically arguing that “the probability of X is non-zero for all X”. That is true (or unfalsifiable) in the same sense that solipsism is true (or unfalsifiable). No one can prove to you that it ain’t so, but it’s an entirely uninteresting and useless position to hold.
It’s not non-zero for all X. If I claim that “according to QM, there’s a non-zero probability two entangled particles have the same spin”, one could just produce the math necessary to show that this claim is false. Likewise, if my claim about QM saying that the probability of an angel appearing is non-zero, I’m sure it’s possible to do that (it might be difficult, though). The same with those Boltzmann brains, but physicists seem to think that their probability really is non-zero. Solipsism, on the other hand, is completely immune to such attacks.
The important thing here is really whether what I’m claiming follows from the math of quantum mechanics or not. Physicists don’t try to falsify every single prediction that quantum mechanics makes, because they already think there’s enough evidence (well, most do) that the theory is correct. There obviously is no such evidence for solipsism.
The probability of our current understanding of QM to be false is non-zero, too.
Things that QM forbids might be allowed by the next theory that follows it (what does Newtonian physics say about quantum tunneling? Absolutely impossible.)
You are granting QM the status of absolute, final truth and I see no reason for that. There is non-zero probability that it is mistaken :-P
I tried to be careful about this. In an earlier post, I said: “But do not that I’m not saying that the angelic being will in fact appear somewhere! That one would follow from quantum mechanics being a complete theory and MWI (or QIT) being a correct interpretation, both of which are surely debatable (and even then it would only happen in a very small minority of all worlds).”
That said, I think it’s quite a radical position to assign much probability to the possibility that QM is wrong. So far it’s consistent with all the evidence that we have, and there’s no evidence to support any of the competing theories or modifications, like objective-collapse theories. Because of this, a hypothetical improved theory might also contain all the weird stuff that QM does, plus some more.
On the other hand, I sometimes wonder if the people working on these theories would be more inclined to question them if they thought more about all the absurd implications they potentially have. (They might not: I recall reading a statement somewhere by Steven Weinberg who thought that eternal inflation or some other multiverse-predicting theory is a miserable theory, but the best that there is and possibly correct.)
I don’t think so, with the slight change from “QM is wrong” to “QM is limited in its applicability, just like Newtonian physics”.
But in any case, in this thread you operate in a black-and-white world of “zero probability” and “non-zero probability”. I am pointing out that the set of zero-probability events is empty.
Fair enough. I suppose one could say that the problems with combining QM and general relativity suggest that QM needs to be modified, but so far we don’t have experimental evidence for anything but pure QM, I believe.
Well, our discussion spun off from a comment where lisper claimed that surely there are situations where death is inevitable. I countered by saying that as far as I know, there’s always some way to survive that has a non-zero probability according to quantum mechanics, so that’s where the emphasis on zero vs non-zero probability originally came. Note that the view advocated in the original post views the formalism of quantum mechanics as an accurate description at all scales and also says that all events with a non-zero probability will happen (but that the ones we end up not observing are not something we should care about).
I think we agree but I was trying to make a bigger point than your reply captures. I doubt that you will even experience the terminal illness assuming there are many more possible futures where you stay healthy and anti-aging science advances than ones where you are miraculously saved at the last minute, by aliens or luck.
That makes the roulette scenario relevant to our experience. Because if you have the conviction to pull the trigger if something doesn’t go your way you have the three options I laid out. So most likely you don’t even have to try—assuming you are sure you will.
Well, I’d rather say that I will perceive being every one of them; it’s just that no future me will perceive being more than one of the future mes. The terminology gets quite confusing here, but I think the Quantum Russian Roulette you mentioned (and quantum suicide and immortality, by extension, for example) is one situation where this aspect of quantum theory becomes somewhat apparent, which is why I think it would be interesting if you elaborated a bit more on how you think the predictions QTI and MWI make differ from each other.
It depends on what you mean by “I”. This is the crux of the matter. MWI takes a God’s-eye perspective and looks at the whole wave function. On that view, there are many you’s (i.e. many slices of the wave function that contain macroscopic systems of mutually entangled particles that perceive themselves to be you).
QIT takes the perspective of the-you-that-you-currently-perceive-yourself-to-be. You will only ever perceive one of that kind of you.
For the purposes of making decisions it makes more sense to take the latter perspective because it’s the-latter-kind-of-you that is making the decisions and has to live with the consequences.
I would say that a major difference between MWI and various collapse interpretations is that there are situations where according to collapse interpretations there most likely will be no future you; but according to MWI there surely will, although their amplitude is low (the aforementioned Russian roulette is one such situation, for instance). I find it somewhat difficult to think about those from the perspective you advocate.
No. Not “will”. IS. If you’re going to take the God’s eye view then you have to let go of your intuitions about time along with your intuitions about classical reality. The wave function is a static four-dimensional thing. Time emerges from the wave function in exactly the same way that classical reality does. You have to be careful not to apply terminology from the mortal’s-eye-view to the God’s-eye-view. That’s how you get yourself into trouble.
UPDATE: Here is a popular article about how time emerges from entanglement.
I think what I said applies when you take a first-person point of view. If you’re a participant in a quantum suicide experiment, then if you expect a collapse interpretation to be an accurate description of reality, you should expect to eventually be hit by a bullet and die. But both MWI and QIT predict that you will continuously notice that the gun doesn’t fire. The difference is not in the point of view taken, it’s in the fact that the parts of the wavefunction that contain a (from first-person eye-view) future version of the participant actually are there.
No, that’s not quite true. QIT predicts that if you notice anything then you will notice that the gun didn’t fire. But QIT does not guarantee that you will notice anything. You could just die.
Notice (!) that when you start to talk about “noticing” things you are tacitly bringing consciousness into the discussion, which is a whole ‘nuther can o’ philosophical worms.
See also my response to akvadrako.