I guess I’ve always been confused by the Many Worlds Interpretation of Quantum Physics and the fact that it’s taken seriously. Like is there any proof at all that universes outside of our own exist?
I admit that I might be dumb, but, how does one look at atoms and say “My God! There must be many worlds than just our one?”
I just never understood how Many Worlds Interpretation was valid, with my, admittedly limited understanding, it just seemed to be a wild guess no more strange than a lot things we consider too outlandish to humor.
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Many Worlds isn’t taken seriously because there’s “proof” of other universes - it’s taken seriously because it’s actually the simplest explanation mathematically. The equations of quantum mechanics naturally lead to superpositions (particles existing in multiple states). MWI just says “what if we don’t add extra rules to make those superpositions collapse?” It’s like if you have a math equation that gives you 5 answers, and instead of creating a complicated rule to pick just one answer, you just accept all 5. Thats why physisists consider it - parsimony.
None.
It is, however, actually simpler than other theories, in that if you just let quantum mechanics do it’s thing without extra (unknown) parts to limit it, it produces many worlds. So, by Occam’s razor…
Specifically:
Quantum systems are in more than one classical state at a time, unavoidably. You can see this in the double slit experiment. Even if you send a single particle at a time through the slits, it passes through both and creates the interference pattern. (There’s also ways to formally prove that making quantum mechanics normal would require fate, or faster-than-light trickery which would actually be worse than fate)
Early physicists were very confused by this. The Schrodinger’s cat was used as a thought experiment meant to illustrate how that’s absurd, and it was decided there must be something that causes quantum states to “collapse” to one state before they can cause any trouble.
That’s not definitely wrong, and it’s still debated in versions by modern theorists, but it turned out not to be necessary. The reason for that is that if a part of a quantum system becomes entangled with something outside of it, the interference will no longer happen, and it becomes indistinguishable from multiple slightly different copies of the same system.
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Per rule 9, could you provide a source for your interpretation of the double slit experiment, specifically that “there is no sort of wave collapse” and “the photons absorbed by film or eyes were just not impacting the surface because they were absorbed elsewhere, causing less friction between the photons and changing the patterns on the surface.”?
This appears contradictory to the standard quantum mechanical explanation for the interference pattern, which is that the wavefunction of the photons passes through both slits, interfering with itself and changing the probability of detection or interaction at specific points along the film/sensor.
The effect isn’t unique to photons and has been observed with electrons, atoms, and even large molecules. As long as the slit size and spacing are comparable to the wavelength of the particle wavefunction it’ll work.
The photon wavefunction being a superposition of position states that self-interact, and then collapse into a single state/location when interacting with a non-quantum object are fundamental to quantum mechanics, and are part of the reason this experiment is such a great introduction to QM. The many worlds interpretation of wavefunction collapse is not fundamental- it’s one of many interpretations for what the math of QM means and not even the most popular amongst theorists (that’d be the Copenhagen Interpretation).
No, it’s not. Exactly one photon (or electron) still arrives. You can refer to Wikipedia for this one. And refer to the no-go theorems if you’re trying to push a homebrew hidden variable theory.
The Schrodinger thought experiment was intended to point out the ridiculousness of observation theory being applied in quantum theory, not an attempt to prove it.
Yes, which is why they had to come up with collapse, and later multiple worlds theory. Just not doing QM isn’t an option.
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Okay, cool, whatever. Maybe go write a paper about that. I’ll even read it so you don’t have to bother actual peer reviewers.
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Your first sentence is a rule 1 violation (“be respectful and inclusive”), could you amend or remove it? Criticize the ideas (preferably with sources) but not the person. Thanks!
And the comment I replied to violates rules 3, 6, and 9. Why am I being singled out?
Edit: I am incorrect, my apologies.
You are not being singled out. I’ve given the author of the other comment a warning with the opportunity to fix the rule violation with an edit, same as you. In both cases, the comments will be removed if they aren’t addressed in a reasonable timeframe.
I don’t know where to start. There are so many things wrong with this comment that I’m confused as to how you even became confident enough about these falsehoods to write them. Where in the world did you get this idea of the Double Slit Experiment?
Just to be clear, what you are saying is literally that Quantum Physics in general is false, which flys in the face of the last century of science. This is literally flat earth tier
Crackpots seem to fundamentally misunderstand how science works, and mistake a hunch (maybe the photon has just been absorbed somehow, or it’s like friction somehow) for a discovery. They also seem to think everyone else who’s looked at a problem is stupid. In both cases, I kind of get it, because there’s cultural forces promoting that - we’re told you’re allowed to believe whatever you want about metaphysics without needing to support it, and we’re told that certain individuals can see a persistent problem and come up with a billion dollar idea to solve it all on their own.
Hopefully I’m not breaking any rules by guessing a diagnosis here.
There isn’t any “proof”; in fact, Many Worlds is what’s called “unfalsifiable”, which means we don’t have a way through the scientific method to show Many Worlds to be false.
Also, it’s not really
My God! There must be many worlds than just our one?
But more
There are moments in time where one path is taken and not another… but what if all paths are taken, somewhere?
It’s not meant to be a valid theory, it’s just a possible outcome of having a spacetime continuum; because it’s not falsifiable though, it’s not worth pursuing right now, only worth keeping in mind in case we come across new evidence to evaluate.
Thank you for making the point so cleanly. I was about to piss a lot of people off
Many Worlds is what’s called “unfalsifiable”, which means we don’t have a way through the scientific method to show Many Worlds to be false.
For one thing, any experiment which demonstrated objective collapse (which aren’t just possible in theory, they’ve actually been performed) would falsify MW.
I’m aware of the double slit experiment and its variations, but I probably do misunderstand Many Worlds to at least some degree; how does wave collapse prove Many Worlds to be false?
Well, under Many Worlds, wave function collapse isn’t a real “thing”; it’s just an illusion caused by the observer becoming entangled with the wave function. Objective Collapse theories, however, propose a real physical mechanism of wave function collapse. If that’s true, and there was found to be a real mechanism of collapse, then MW would be impossible, because the wave function would collapse before any “branching” could happen.
And what is there to stop the collapse from being the branch point? In one world, it collapses one way; in another, another. There doesn’t seem to be any inconsistency there.
Well, because under Many Worlds, the wave-function not collapsing is the reason there are multiple branches; the wave function is the multiverse. So if the wave function has collapsed into a single, definitive state, then there is only a single, definitive universe.
Sorry, that doesn’t prove that there’s not actually Many Worlds out there. The whole point is that there would be a single, definitive universe state for every possible valid configuration after wave-function collapse. The reason it’s unfalsifiable is that it cannot be proven currently whether or not it’s a literal plurality of alternate worlds. I would also argue that if there’s but one “definitive universe” state then it’s not really a Many Worlds theory at all, but just a different theory of the Universe.
I’m not saying you’re wrong, or that this interpretation of Many Worlds is wrong - I’m just saying we’ve not yet developed a way to prove it one way or another. And if we did develop that technology to prove it one way or another, that would in itself unlock a whole new world of questions to answer. Thinking about what those questions might be is worthwhile science, in my view.
I think you misunderstand me. I’m talking specifically about the Many Worlds interpretation of Quantum physics specifically, the one originally formulated by Hugh Everett. I’m not talking about just some general notion that “there might be other universes”.
It’s just an indisputable fact that the MWI requires their to be no wave function collapse, and if you don’t understand why, you really have not learned enough about it to be in a position to declare it “unfalsifiable”.
Seems like it’s splitting hairs and saying the “many worlds” part of MWI doesn’t count, as that is only a prediction not postulated.
No? I’m not sure how you got that from my comment
I’m taking about the linked page.
I mean, to be fair that is what the linkes page says, but people are misunderstanding the hypothesis everyone calls many worlds (also what the page says) as Many worlds is just a follow up of the theory not the theory itself.
Like Einsteins Relativity didn’t say in the theory that we would be able to predict Mercury’s orbit, but it comes from it.
By the linked argument, introducing any sort of nondeterminism into classical physics would predict many universes.
If I flip a coin, a classical statistical model would predict I have a 50/50 chance of getting a heads or a tails. I can predict different things will happen as things react to the heads/tails result, and describe different “universes” where each of those outcomes happen.
Do those “other universes” really exist? Or are they simply a figment of my statistical analysis of the situation? That’s the part that’s unfalsifiable.
By the linked argument, introducing any sort of nondeterminism into classical physics would predict many universes.
Not necessarily, objective collapse theories can be non-deterministic without predicting many universes. The extra universes only appear if the wave function never collapses, and stochastic collapses are entirely possible.
If I flip a coin, a classical statistical model would predict I have a 50/50 chance of getting a heads or a tails.
Yes, but critically - under classical mechanics - this is only because you have imperfect knowledge of the system. From the perspective of Laplace’s Demon, the result of the flip is 100% deterministic and the chance of it landing the other way is 0. But this is not the case in quantum physics unless a hidden variable theory turns out to be true (and thus any experiment which discovered hidden variables would also falsify MWI)
Do those “other universes” really exist? Or are they simply a figment of my statistical analysis of the situation? That’s the part that’s unfalsifiable.
Well, no. Because you’re talking about classical mechanics, where probability is just about imperfect information and isn’t part of the underlying ontology. So no, those universes don’t really exist. That’s completely different from quantum physics, where the wave function actually exists - it’s not that the electron only goes through one slit and we just don’t know which one: it really does go through both slits.
where probability is just about imperfect information
All it takes to produce the many worlds is the assumption of true nondeterminism that isn’t simply “imperfect information”.
Conversely, if you interpret quantum mechanics as a rethinking of statistics rather than some additional physics for the universe, you can make sense of the world without the need for a multiverse.
All it takes to produce the many worlds is the assumption of true nondeterminism that isn’t simply “imperfect information”.
Incorrect. As I said, objective collapse theories can be non-deterministic without predicting many universes. The extra universes only appear if the wave function never collapses, and stochastic collapses are entirely possible.
if you interpret quantum mechanics as a rethinking of statistics rather than some additional physics for the universe
But you can’t. Quantum physics cannot be explained by classical mechanics alone. If it could, we never would have formulated quantum physics to start with.
Incorrect. As I said, objective collapse theories can be non-deterministic without predicting many universes. The extra universes only appear if the wave function never collapses, and stochastic collapses are entirely possible.
Yea, the difference between a classical statistical theory with and without many worlds is whether or not you maintain a state that includes all possible outcomes as you continue your analysis, or restrict the state you are analyzing to one possible outcome from one of your statistical events. The same is true of quantum mechanics.
But you can’t. Quantum physics cannot be explained by classical mechanics alone. If it could, we never would have formulated quantum physics to start with.
I’m arguing that quantum mechanics is a rethinking of statistics more so than a rethinking of physics. The world cannot be explained without it.
I think that even if I must consider a state that includes all possible outcomes while doing my analysis of the situation, that doesn’t mean those “alternate worlds” necessarily physically exist in any meaningful way.
Yea, the difference between a classical statistical theory with and without many worlds is whether or not you maintain a state that includes all possible outcomes as you continue your analysis
Yes, but, again, this is only because you have imperfect information about the underlying physical system. The array of possibilities presented by classical statistics are strictly epistemic; the actual real state of the system you’re analyzing is always definitive and determinate.
And very, very importantly, this is not that case in quantum physics. The indeterminacy of state in a super position is not just the result of imperfect information; it is a fundamental part of the underlying system. It is not the case that, in the double slit experiment, the electron only travels through one slit, and we just don’t know which one. It really really does travel through both. This is fundamentally different from classical mechanics.
I’m arguing that quantum mechanics is a rethinking of statistics more so than a rethinking of physics.
Look, if you want to try and argue that quantum physics isn’t physics, I won’t stop you, but you’d better have an extraordinary argument, because this is an extraordinary claim. One that rejects the last century of scientific consensus. If you can demonstrate that quantum mechanics is just a different statistical model of classical physics, it would be a revolution in science.
I think that even if I must consider a state that includes all possible outcomes while doing my analysis of the situation, that doesn’t mean those “alternate worlds” necessarily physically exist in any meaningful way.
That’s correct, and MWI doesn’t argue otherwise. The important part isn’t just that these states are possible, it’s that they have real physical existence.
You can probabilistically prove the many worlds exist, because it implies quantum immortality. Just connect a short-half-life Schrödinger mechanism to a nuclear bomb, and some of you will survive for a statistically impossible number of half lives. That version of you will have proven the many worlds to be true.
Right, and you can find out what it looks like beyond the event horizon of a black hole by just throwing a probe in that can survive the approach. Mind you, you’re not getting any information back out of the black hole, but it’ll be there in the probe’s databanks regardless. I suppose you can have it back over the span of the rest of the black hole’s life; though, you’ll need to record everything else coming out of it and somehow cohere all that information back together in the right order.
Which is only about as difficult to get anything scientifically useful from as your probabilistic proof machine. Both involve lots of radiation though, so they’re basically the same thing! (👉ﾟヮﾟ)👉
Except you might be the version who survives!
Except you might be the person who survives!
Except you might be the person who survives!
I don’t think it proves many worlds any more than it proves you have a fairy godmother manipulating quantum states for you. All you’ve done is shown an unlikely occurrence happened, not what caused it.
All you’ve done is shown an unlikely occurrence happened…
That’s all science is. Collect data, and show how it’s unlilely unless your hypothesis is true. Five sigma later, and you’ve made a discovery.
Collect data, and show how it’s unlilely unless your hypothesis is true.
The quantum immortality experiment doesn’t do that, though. The outcome, by definition, always occurs within the realm of random chance. Your environment needs to create an outcome that is extremely unlikely to occur by random chance. The experiment is not repeatable. It makes no predictions about what’s going to happen if you try again. It doesn’t do anything useful to bolster the many worlds theory.
Your environment needs to create an outcome that is extremely unlikely to occur by random chance.
If you survive 32 half lives, I’d call that extremely unlikely! Give a try.
The experiment, as defined, only leads to your survival by random chance. The experiment does not create any outcome except by random chance so it cannot be used to prove anything.
Every half life you survive is an experiment.
Great answer, but it unfortunately is taken seriously. The reason is because it is an “end of the road” hypothesis. It tells you all the weirdness is fundamental and no further thought is required. Just like good old Copenhagen. The unfalsifiability is a virtue here, it’s a complete explanatin without the messy testing. Now stop thinking, shut up, and calculate.
To be clear, the reason Many Worlds hypothesis exists in the first place is because it’s a possible solution to the calculations. It’s not that someone just came up with an idea to get out of doing real work. It’s just unfortunate when the universe puts multiple possible solutions out of reach of experimentation. But hey, there was a long time of history where virtually any belief about the composition of the moon was considered unfalsifiable.
The “solutions” are not out of reach. Just do the experiment more than once, like any statistical theory.
The moon thing: yes because it was hard to get to, not impossible in principle. If the moon was in a parallel universe your analogy wouldn’t be irrelevant.
but it unfortunately is taken seriously
Why is that unfortunate? It’s an extremely well justified theory.
It tells you all the weirdness is fundamental and no further thought is required.
I’m not sure why you say this? If anything, that’s a description of Copenhagen, which MWI is a response to.
https://arxiv.org/abs/1301.1069
Effectively there is no current consensus on the issue, though Many Worlds and String Theory are widely regarded outside their adherents as non-falsifiable and therefore not legitimate theories.
Essentially the proponents of the theory have created beautiful math that fit their view, but absolutely nothing in the real world that can show that it is a more valid theory than any of the other theories which have equally elegant math to back them.
though Many Worlds and String Theory
String Theory has nothing to do with interpretations of quantum mechanics.
are widely regarded outside their adherents as non-falsifiable and therefore not legitimate theories.
Only by people who don’t understand them.
Essentially the proponents of the theory have created beautiful math that fit their view
No? Many Worlds has nothing to do with math. You seem to be getting your criticisms mixed up. To be blunt: if you can’t even remember what your criticism is actually meant to apply to, you should probably read into it more before commenting.
None. There is absolutely no proof of many worlds or the multiverse. RE the god of the gaps. It’s much more interesting to do physics rather than speculate about what falls outside the purview of the scientific method.
I do not understand how people can be so arrogantly confident about topics they clearly have not learned the basics of
How do you know I don’t know the basics of physics?
Because I read your previous comment
But more than half of the comment was about doing physics
No, none of your comment involved actual physics.
Is there anything in particular you’d like to know about?
[H]ow does one look at atoms and say “My God! There must be many worlds than just our one?”
Electrons. You’ve seen the model of the atom, right? Cluster of balls in the middle (protons and neutrons) and the electrons are little balls that whizz around like little planets around a Sun?
That model is a simplification of the truth. It turns out that it is impossible to pin down where an electron is and also know what it is doing. And if you know what it’s doing (you can see its effects), you’ll have no idea where it is.
Where they are has to be measured by probability. “It’s bound to this nucleus / taking part in a chemical bond so it’s likely to be in this vicinity”, is about as close as you can get.
There is literally nothing excluding that electron from temporarily being a billion miles away. That’s astronomically unlikely, but it’s not impossible.
And by some measurement methods, when you do try to pinpoint where the electron is, it can appear to be in multiple places at once.
This can be interpreted as bleed-through from nearby quantum realms, maybe even other universes, where the electron is in one place per nearby universe. One of those places is ours, but we cannot tell which. And by the time we’ve made any kind of determination, the electron has moved. They never stop.
Photons - particles of light - also do this. All subatomic particles do this.
The more subatomic particles you have in some combined state (as an atomic nucleus, or even a molecule), the lower the probability is that that bound state can be in multiple places at once, but again, it is not ruled out.
But it does mean that the more bound particles an object is made from, the more definite its position appears to be, which is what we’re used to at our human-sized scale.
I’m trying to follow, how can an electron be a billion miles away? Aren’t the attractive forces keeping the atom together?
In quantum physics the position of an electron is defined by a wave function. This wave function or rather it’s square modulus is the probability distribution of the position of the electron. In more simple terms, the electron doesn’t have a precise position but rather a high probability to be somewhere.
One example of an electron being able to be billion miles away is the following: Think of a probability in the shape of a bell. Where the center of the bell has a value between 0 and 1 and to each side the function tends to 0. The likeliest region for the electron to be is the center of the bell, but since the function never takes the value 0, it is not impossible for the electron to be a billion miles away.
If you apply a force to the electron, like an electrical field, you will simply shift and modulate the probability distribution moving the maximum probability towards the positive side of the electrical field. But the electron being in the place you expect it to be is still nothing but a very likely event. The event of the electron being a billion miles away is still of probability not 0.
Draw a graph by flipping a coin. Start at (0,0). Assume a fair coin and fair flips. Move one unit right each time, but go up (+1) for heads and down (-1) for tails. The line drawn can go arbitrarily far vertically from 0, but the average vertical position necessarily remains 0.
The average position of an electron is slightly more nebulous than the line x=0, and depends on what, if anything, the electron bound to, but for each state an electron can be in there is a group, or a locus, of possible positions that represent that bound state and the whole locus is a mean of sorts. An electron can go on a journey wherever as long as it continues to regress to that locus.
And in the exceptionally rare instance where a subatomic particle goes on an indefinite journey, we call that quantum tunnelling.
Quantum tunneling is actually a problem in integrated circuit design: https://medium.com/@markveerasingam/quantum-tunneling-the-semiconductors-struggle-in-the-miniaturization-race-7ef2df8f9e48
I heard about that too. Its absolutely mind blowing when you realise, that we are able to build chips on such a small scale (and not just for special chips but for relatively common chips), that we are dipping into the realm of quantum physics causing all sorts of problems.
The “many worlds interpretation of quantum mechanics” is loosely that when you do a quantum coin flip, the universe splits into two universes, one for each result.
The reason for this thought is when you work with quantum mechanics, your system has a state that evolves smoothly, but if you “measure” it, the state suddenly snaps to (a random) one of the possible measurement values (when the coin isn’t being observed, it smoothly evolves, but once you measure it, it suddenly takes on a random value). However, if you expand your quantum description of the system to include your measurement device as well as the quantum “coin”, that sudden “snapping” goes away. Instead your whole system smoothly evolves, and it evolves into a “superposition” of the shared state of the state of the overall system in each of the possible measurement outcomes.
Extending this idea, it would seem that whenever you could describe a situation that acts like a “quantum coin flip”, both results happen, and the universe “splits”.
I really want to emphasize that the practical meaning of these “other worlds” is just that things are a lot “fuzzier” when you zoom in than classical statistics would suggest. Not that there’s another universe where you stayed with your ex or took a different career path or whatever.
Also this is an “interpretation” of quantum mechanics for good reason. It doesn’t really have any physical implications. In particular, it’s not possible to go “interact with” those “other universes”.
Most importantly, there are other “interpretations” of quantum mechanics, like that quantum mechanics is really a rethinking of statistics not of physics.
If you want to go into depth on this, I recommend you look up Sean Carrol talking about the subject - or read his book Something Deeply Hidden, if you’re up for it - he’s one of the best science communicators I’ve heard and a strong proponent of many worlds.
But to try to summarize it in very short: the “multiversal” behavior is already baked into quantum mechanics - a particle can be in two places at once, as in the double slit experiment - just at a very small scale. Traditional quantum physics postulates that there’s some mechanism by which this behavior is cut off before it reaches the macroscopic scale (wave function collapse). Many Worlds just asks “Do we actually need this postulate? What would it look like if we didn’t have it?” And the answer is, it would look like the universe we experience, just with a multiverse along side it.
Doesn’t Carrol have a reputation for being rather crass or am I thinking of someone else?
You’re thinking of someone else. Watch all the Carrol you can: he’s an expert on interpreting Physics and specifically on Many Worlds.
Not that I know of.
Multiverse and many worlds interpretation are two different things.
The idea of multiverse is that there are many other universes existing in parallel with ours. Either the universes are created through different big bangs, or maybe the universe is constantly splitting into many other universes. This is mostly science fiction.
MWI is one of many competing ideas to help coming to terms with the counterintuitive nature of quantum physics. A particle can be in many places at once when not observed. Once it’s observed, it chooses to stick in one place. MWI is one interpretation of why this is happening.
I’m pretty sure the multiverse theory is baked into the big bang theory and cosmological theories, so I wouldn’t necessarily call it mostly science fiction.
Cosmological hypotheses suggest universes with different initial conditions are possible (different space-time geometries, different elementary particle masses, etc.). The big bang theory suggests multiple universes (not just ours) with different initial conditions were formed due to eternal inflation. As the multiverse continues to undergo this eternal inflation, there forms pockets where the inflation has ended and is “hospitable”. Our observable universe would be an example of such pockets, but since inflation is eternal, there should be many of these pockets.
I call it science fiction because there’s no real evidence for it. Not yet at least.
Most ideas of multiverse comes from making educated extrapolations of currently known science. But that’s not enough. Scientists must also design experiments which confirms the extrapolation to be correct. This hasn’t been done.
Maybe it’s harsh to call it science fiction. Correct wording is theoretical physics.
Hehe, yeah, it’s a bit harsh to call it science fiction, especially this day in age when a lot of new physics lives in theoretical physics.
Cosmological models are very difficult to test given their nature. In many cases they are tested in massive physics simulations. The general test is to simulate the cosmological theory and see if it produces a universe that has the same observable qualities as our current universe once the simulation reaches our present epoch.
Nevertheless, Hawkins had his own reserves regarding his theory due to it not being experimentally falsifiable; but one must understand that rejecting the multiverse theory = rejecting the big bang theory since they are currently coupled.
I admit that I might be dumb, but, how does one look at atoms and say “My God! There must be many worlds than just our one?”
Well, we looked at atoms and found out that the only meaningful way to describe them is with quantum mechanics. This is the most precise and possibly best tested physical theory ever developed. And it says that if an atom starts out in state A, it will then naturally evolve into a state A+B.
Now, A and B are mutually exclusive. So what does that mean? One reasonable way to view it is that it is indeed physically in both states A and B as the theory says. That’s ultimately what leads to the many worlds interpretation. The atom is both in state A and state B, and the universe accepts both of the different trajectories of reality that leads to.
This view is equivalent to a number of other ways of view things, all of which lead to the same prediction of physical behaviour for now, so essentially you can just pick your favourite.
great lecture on the concept of superposition: https://youtu.be/lZ3bPUKo5zc
If you want to know why it’s taken seriously:
https://m.youtube.com/watch?v=kTXTPe3wahc
Tl;dr: you need to actually understand the physics at play that lead to serious consideration of the many worlds theory. It’s not the pop-sci it gets painted as. It’s much more specific.
“It’s not as pop-sci as painted” anyway here’s some pop-sci to justify it…
The reply to the energy problem is hilarious. These universes that differ by a single quantum event have radically different energy totals. Science!
If you want the real answer then take some physics courses instead of being an uninformed dumb dumb.
If you want a quick answer then I posted a high level explanation that’s well regarded amongst physicists.
Two points:
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The MWI/Everett interpetation is the simplest interpretation of quantum mechanics—other interpretations have to add additional assumptions to prevent it from happening.
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The most common version of the MWI is actually an interpretation of an interpretation (i.e., Bryce deWitt’s reinterpretation of Hugh Everett’s 1957 thesis), but many of those who subscribe to deWitt’s interpretation (including deWitt himself) don’t seem to grasp how it differs from Everett’s. Everett’s thesis makes no explicit reference to multiple worlds—just a single wave function that can be measured in different bases to produce multiple versions of each observer, each of which perceives a different version of the universe. For Everett, the wave function was ontologically prior to the material world, so his universal wave function was a complete explanation as-is. But for deWitt (and for most people), the material world is ontologically prior, while the wave function is just a tool for describing its behavior. So by their reasoning, those multiple perceived worlds must all really exist as parts of the wave function in some sense.
MWI is not simpler than other interpretations. It’s more purely mathematical and thus simpler if you ignore experimental physics, yes. But if you consider physics an empirical science, the interpretation has to get pretty complicated to explain why all outcomes of an experiment happen, but only one is ever observed.
It doesn’t require fewer assumptions or ad hoc collapse mechanisms, it just moves those to a place where they’re harder to see.
The interpretation has to get pretty complicated to explain why all outcomes of an experiment happen, but only one is ever observed.
But they are all observed, that’s the point.
By who? If I measure the spin of an electron in a superposition of up and down, I only ever get one result, up or down.
By the versions of you in each branch.
But which one am I? You postulate that “I” am somehow split into endless copies upon observation, but also “I” am only one of those copies somehow chosen at randomly according to the wave function distribution. So “I” see all outcomes of the experiment but “I” also only see one of them?
This is where it stops being simple to me.
What you are describing is essentially another facet of The Vertiginous Question - why am I me instead of someone else. Importantly, this is a problem that exists regardless of whether MWI is true or not, so the lack of simplicity already exists, like it or not.
Before you were born, the future contained the creation of a vast number of conscious beings, but only one of them would be “you”, seemingly chosen at random.
The branching of the observers wave function is exactly the same situation.
It’s a question about Philosophy of Consciousness, which is well and truly outside the purview of Quantum Physics. From the scientific perspective it’s perfectly logical and sufficient to say that “there is one observer who will split into many, each of which will have its own perspective that is unaware of the others”.
I think you misunderstood, it’s not the Vertiginous Question, it’s simply about describing an experiment.
I perform an experiment to empirically investigate something, this process depends on me subjectively experiencing the result of the experiment. Before the observation, the system is in superposition, afterwards it appears to not be in my subjective experience. Collapse theories have to add a postulate that something happened upon observation to change the system. MWI has to add a postulate that some mechanism placed me in a certain branch of the possible outcomes. Neither is necessarily simpler than the other.
Whether other versions of me with their own subjective experience observed something else or not, you need to add that postulate. Their observations are irrelevant empirically, and saying “you actually observed all outcomes” is just factually wrong from an empirical viewpoint.
The MWI/Everett interpetation is the simplest interpretation of quantum mechanics—other interpretations have to add additional assumptions to prevent it from happening.
How is the existence of an infinite amount of other worlds a “simple interpretation”, that seems like a literal infinite amount of assumptions
Put it this way: is the idea that the stars in the sky are dots on the inside of massive solid sphere more simple then the idea that they’re all just other suns very away? The simpleness of a theory isn’t determined by how many objects it predicts.
Calling Everett’s interpretation the “many worlds interpretation” is like calling a particle’s wave function the “many particles interpretation”—it’s not wrong, but it makes it sound like you’ve got a multitude of separate things when you’ve really just got one thing of a different kind.
If we sufficiently torture the word “simplest”.
Or, you know, use it accurately.
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I don’t understand how it’s any more outlandish than thinking that we can be aware of everything that exists, or that everything exists in a straight line through time, never branching. Maybe it’s a lack of understanding on my part, but it seems the sum total of what we have discovered through science, or even through imagination, only illuminates a very small subset of reality. We can only measure with the instruments we can imagine and build, and with our own limited senses. So I wouldn’t jump to believe, nor to label unbelievable.
This was mentioned (not fully, but enough to get some of the ideas) recently in an episode of PBS Space Time
As far as MWI itself, my understanding is that it comes from simply taking the same math that works for atoms (as you say) and applying it to everything - the observers of a quantum system, the earth, the whole universe. I think it really comes down to the question: If Everything is a wave function, what would it look like from the inside? And MWI pops out of trying to answer that.
And the other interpretations of quantum mechanics don’t even seem better to me, requiring arbitrary conditions for a state to collapse to a single value for example. That feels to me like an entity of the type Occam meant.
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Sounds like you don’t understand the basic concepts involved, given that Many Worlds Theory has nothing to do with “other types of energy on the electromagnetic spectrum”. Like, at all. Not even a little.
To be blunt, if you do not understand what is being claimed, you should try to learn, not make assertive statements about things you don’t understand. It’s frankly incredibly arrogant.
