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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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.
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.
Thank you for making the point so cleanly. I was about to piss a lot of people off
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 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?
Not that I know of.
You’re thinking of someone else. Watch all the Carrol you can: he’s an expert on interpreting Physics and specifically on Many Worlds.
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.
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.
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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.
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.
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.
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.
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?
I had a though experience years ago on mushrooms, that our universe lives in a blackhole. Just think about it, when stars big enough implodes it creates a black hole in the fabric of space, where nothing can escape (not even light).
The beginning of our universe is somehow related to a condensed hot/light that explodes and creates the actual expansion we see right now… Kinda curious right?
Also there’s somehow a limit how far we can see through our universe, that’s also odd… It’s impossible at the moment to see outside our own universe, because remember nothing can escape outside a blackhole, not even light !! Soo yeaah that’s why I think we live in a multiverse.
Also on a final note, Rick&Morty said so 🤷♂️
Just a correction, there isn’t anything limiting how “far” we can see our into the universe except our limited technology. And even then we are very close. We’re only limited by how old our universe is, as it takes light that long to travel to us from the edge of the expanding universe. The furthest we can possibly see would be about 300,000 years after the big bang, when light was finally able to travel unimpeded throughout the universe.
Thats way I said “for the moment”, because I know we are limited by our technology. However, even If our technology evolves to a degree so large we can not comprehend, I’m pretty sure we wouldn’t be able to “see” outside our own universe.
Sorry If my wording is a bit janky and not very scientific. Following your guts is also not very scientific in anyway, but that’s how I feel when seeing all those strange coincidence that cross each other strangely enough !
But thanks for the clarification !
Edit: Even if we can’t see outside our own bubblrle, we will still be able to travel from one universe to another :p
You’re asking a couple different questions at once…
But basically assume that there are multiple (maybe infinite) big bangs, and each time that happens, the resulting universe has its own laws of physics. We wouldn’t see slight changes, things would be drastically different, but since they keep popping up. Eventually we’ll see every permeation happen. Including identical everything to ours, but just one random difference that created the TV version of alternate realities.
You might think entropy prevents that, but “entropy can’t be reversed” is less a fact and more “the simplified version laypeople are told in science class”.
And a different option would be that rather than one straight line of time, any possible choice can branch and create its own timeline that can then branch, etc.
And that might seem like we’re “stuck” but nothing in physics even requires one way direction of time. The only reason we need to perceive it in only that way, is without linear time consciousness couldn’t happen. Without cause and effect, consciousness can’t exist
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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.
