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What proof is there of the multiverse?
(sh.itjust.works)
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this post was submitted on 03 Aug 2025
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Two points:
The MWI/Everett interpetation is the simplest interpretation of quantum mechanics—other interpretations have to add additional assumptions to prevent it from happening.
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.
If we sufficiently torture the word "simplest".
Or, you know, use it accurately.
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.
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.
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.
All results of the experiment will be experienced by a future version of you.
No, this is definitely the Vertiginous Question. The "mechanism" that puts you in a certain branch is the same one puts you in a certain body. Are you also going to demand that neuroscientists answer the Vertiginous question before they can say that other people exist?
That "postulate" already exists if you believe in consciousness in the first place.
Literally the opposite: empiricism requires objectivey, trying to insist that only the things that you personally subjectively experience counts is as far from that as you can get.