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.
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
But more
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.
That’s not actually true
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?
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.
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 indisremovedble 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”.
Well, I did allow for that earlier. I’m not a physicist. However, I wouldn’t be so sure I don’t understand why. Reading back over the thread as a whole, you’re right - I did misunderstand you. Let me put it in my own words for you:
But you said above:
and
Could you link the experiments which have definitively shown objective collapse and not just an entanglement illusion? Fair warning, I may need to ask for a layman’s explanation of how they proved the collapse was objective and not just the aforementioned illusion.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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.
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 are glossing over my point. I’ll try to put it as concretely as I can think of:
Assume for the sake of argument that there is a process in an otherwise classical physical system that is truly nondeterministic, meaning there is randomness that isn’t due to any hidden variable or otherwise incomplete knowledge of the state of the system.
When describing such a system, you will run into the same dilemma of either needing a “wavefunction collapse” or “many worlds” interpretation of your statistics.
And yet this model is not quantum. It is a classical nondeterministic model.
My point being, it’s the existence of true nondeterminism that leads to the “many worlds” idea, not the other strange properties of quantum mechanics.
I really, genuinely, think this is not a controversial take. The idea that quantum mechanics is more of a rethinking of statistics than physics comes from my own personal experience studying quantum physics. Most of the time, you take the classical Newtonian mechanics equations (sometimes including “corrections” for relativity), and treat them with the “quantum mechanics” version of statistics, and out pops all the important things you’d like to model, like how electrons arrange into orbitals in an atom. The results of slit/entanglement/bell experiments depend on having an object that obeys quantum statistics, but it can be a wide variety of objects with vastly different physical properties and behaviors (e.g. slit experiments have been done with both photons and electrons).
I don’t think there is any reason to believe the “other worlds” needed to analyze quantum systems “physically exist” to any meaningful extent. It’s the same as considering all possible outcomes of a classical truly random event (if you assume there exists true nondeterminism, not simply a lack of complete information).
Here’s an interesting example:
The Bell test about entanglement is one of the best-known proofs that quantum mechanics can’t be explained using classical statistics.
The Bell test is an analysis of the correlation between two entangled particles.
However, that correlation is only notable because we are analyzing the evolution of both particles.
If we analyze one particle, alone, we wouldn’t be able to determine if it is entangled with any other particles (and we wouldn’t be able to model it without the need for quantum mechanics).
In other words, you only need the “other worlds” when you are analyzing a system and trying to predict its behavior. You can completely ignore all information or “other worlds” external to the system you are studying.
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.
Why is that unfortunate? It’s an extremely well justified theory.
I’m not sure why you say this? If anything, that’s a description of Copenhagen, which MWI is a response to.
Untestable universes is not a rejoinder to “stop thinking” it’s just another way to achieve it
Thank you for making the point so cleanly. I was about to piss a lot of people off
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.
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.
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.
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.
The chance you’ll survive a half life is exactly the same whether MWI is real or not. It doesn’t give you any useful information. You have no way of distinguishing between being just that lucky or MWI being true.
That’s not the case with other experiments. If you assume your hypothesis is correct, the chance of the experiment being successful is higher than the chance of it happening by random chance if your hypothesis is not. That’s a key difference.