That’s a more physically plausible interpretation than ever “tick” of the universe actually creates infinitely more universes because every fundamental particle is quantum and each one is constantly interacting under the wave function every plank second. And the infinite number of possible events that a single particle would experience is multiplied by the joint combination of all particles in the entire universe. It doesn’t seem plausible.
And on the ‘every tick creates more universes’: we are completely fine with superposition in nanoscopic systems. It’s just uneasy to follow that conclusion to the logical end. Just my two cents. I think just because the conclusion seems hard to grasp, the reasoning to get there is completely sound..
Just like Newton’s equations are accurate to describe gravity and motion but only because the full equations Einstein worked simplify to them at small speeds.
So similarly it would make more sense that quantum equations and relativity are two sides of the same coin and there’s some missing mathematical bridge where at small particle sizes it simplifies to quantum and at large particle scales gravity matters and we get Newton and then further relativity.
Using Occam’s razor that’s at least my prior vs some undefined mechanism of action where all possible interactions of every particle actually creates an infinite superposition of universes where that did happen and you get an infinite number of such superpositions ad infinitum. Much easier to believe the huge gaping hole between two very accurate theories explains how quantum mechanics turns into classical mechanics, especially since we know gravity exists, what it is, and quantum mechanics can’t explain gravity.
He argues that the wavefunction collapses on a timescale of h-bar / E_G, where E_G is the gravitational self-energy of the quantum system.
The real issue here is the preferred basis problem, not an infinity of worlds: a single state vector can be decomposed many ways, and the bare math doesn't say which decomposition counts as "the branches." Decoherence picks it out: once the cat is entangled with its environment, the alive/dead decomposition becomes effectively unique and stable, through ordinary unitary dynamics. No collapse, no consciousness (that's von Neumann–Wigner, not Everett). MWI does have an open problem, but it's a different one: the Born rule, i.e. why |c|^2 should count as probability when every branch is real. Also, the normalization is |c1|^2 + |c2|^2 = 1.
They don't disappear. This is the entire point of MW.
For example, "Many Worlds, the Born Rule, and Self-Locating Uncertainty" notices that the rule doesn't mean anything, but it is rational to behave like it does. It's not a very satisfying position, I'd say.
It is not, it is the Schrödinger equation plus an extra rule that says that classical observers are only certain kinds of quantum states. There's no explanation in the MWI for why a device never reads out that a particle is 1/sqrt(2) |here> + 1/sqrt(2)|there>, even though that is exactly as probable a state as being |here>. And it turns out that this is exactly equivalent to positing wave function collapse / the Born rule.
And no, decoherence has nothing to do with this. Decoherence explains why there is no observable interference at the classical level between these states, not why you can only observe some states.
This is known as the preferred basis problem, for anyone who wants to read more about it.
Any good scientific theory must create falsifiable hypotheses.
Otherwise it’s just a nice story.
For any behavior inside the world, this is good.
But for the world itself and what harbor's it, asking for falsifiability is like measuring the expansion of space using a ruler that inhabits the same space.
Even science, that works in terms of cause and affect, which implies space and time, cannot be used to describe space and time itself.
Vanilla "scientists" have been trying to do that, but that is a dead end.
Which exactly is what general relativity is centrally about and the reason why general relativity is defined in terms of intrinsic properties of the Einstein manifold describing the space of the universe. Intrinsic properties are, colloquially, indeed properties that can be measured "using a ruler that inhabits the same space".
Gauß' Theorema Egregium [1] is an early predecessor of intrinsic properties of general manifolds, and says that the curvature of a surface can indeed be "be determined entirely by measuring angles, distances and their rates of change on a surface, without reference to the particular manner in which the surface is embedded in the ambient 3-dimensional Euclidean space" ([1]).
[1] https://en.wikipedia.org/w/index.php?title=Theorema_Egregium...
In LIGO, we detect the far away distortions propagating through our rulers and the differential effect of those waves.
But Michelson-Morley failed because the ruler distorted synchronously with the signal we tried to measure — since we mistakenly believed EM and matter were different fields.
General-relativistic effects are relevant for the outcome of the Michelson-Morley experiment in the sense that the general theory of relativity is a generalization of the special theory of relativity. :-)
Otherwise: the additional predictions that the general theory of relativity makes about gravity, curvature of space etc. are not relevant for the outcome of the Michelson-Morley experiment.
You seem to think I’ve said something very technical, while I’ve merely pointed out a well-known effect of Lorentz invariance and interferometry: you can’t detect an “aether” signal coincident with the detector, because the detector is distorted synchronously.
Michelson-Morley was never going to work because it relied on the assumption matter wasn’t subject to aether wind — which turned out to be wrong, as matter is subject to relativistic effects and fields unify. You needed that independence to generate the differential the interferometry amplified.
By contrast, LIGO measures an effect far removed and not co-moving with the detector. So it works.
We do that, routinely: that’s how we do cosmology.
Yea, that is why we are not getting any where...
Which alternative way of doing measurements do you propose? As far as I know, measuring intrinsic properties, i.e. "using a ruler that inhabits the same space" is with our current technology the only possible way of doing measurements.
A continuum of variants of myself is bought.
What is the value of assuming that literally every possible trajectory actually happens, but somehow I am only in one of them, while also being a continuum of other ones? If everything is true, than nothing is true.
As far as multiverse goes, there isn't any inherit value in assuming that the wavefunction as given actually happens, it's just a simpler explanation than trying to come up with (arguable unprovable) ways to cull the wavefunction.
If you only like predictions and disparage explanations, I might start calling you names, specifically instrumentalist.
Quantum computing was explicitly proposed as a way to prove the truth of many worlds. As far as we can tell, quantum computing appears to work.
I don't think most people believe QC truly proves many-worlds, but I think it is considered some evidence in its favor, and historically it was I think one of the reasons for the development of QC originally.
OTOH, I don't think any of the other interpretations really struggle to explain quantum computing so I agree it's not much of a distinguishing factor.
Not to get all reddit atheist here, but as far as we can tell, the universe is predictable and explainable by fundamental mathematical laws. (We don't see, for example, unexplainable violations of conservation as Michael Landon pops in and out of existence.)
This could mean there is no god or they don't interfere or whatever, but in any case it's pretty good evidence that we can reason about how the universe works.
That's about as good as you can know anything. Beyond that is the "Are you a brain in a jar" kinds of philosophical arguments that are fun when you're 21 and get old after.
Plus astronomical observations used in cosmology to model the state of the universe milliseconds after the big bang which eventually evolved into our locally observable region of space around 13.8 billion (not 6000) years later?
That doesn't prove the dinosaurs were in fact living beings but this isn't necessary to disprove the other assumptions of the alternative hypothesis. By parsimony that leaves the hypothesis that dinosaur fossils emerged by natural processes like everything else we've observed on Earth to date.
Am I missing a joke? Because this is definitely not a good example of a hypothesis impossible to disprove with available evidence.
(If the response is "how do you test whether all that evidence was faked 6000 of years ago to deceive scientists" then we're not actually doing science anymore but games of make believe)
Instead, we can use other forms of reasoning, such as probability and Ockham's razor. These are perfectly valid approaches.
You seem to agree with me on this point, so I direct your attention to the grandparent comment:
> I'm interested in logical arguments for why I should be convinced that something completely impossible to ever test, not even in theory, is correct.
Since QM goes beyond our material world intuitions, I am personally loathe to clothe nrs in words, until we have more and better experiments. I think prematurely translating it into material-level intuitions just leads to a waste of time and much confusion.
Many worlds is falsifiable, if you can show wave function collapse actually happens (not just decoherence). I believe that in the not so distant future we will get more and more proof that wave function collapse never happens. Quantum computing at scale to me is an indication that Everett was just right..
With many words, every postulate has been tested and very verified. What more can you ask from a theory?
Now objective collapse is a testable postulate but none expects that to pan out.
This can be done in any other interpretation? Any unitary evolution on an isolated system can be reversed. This is a mathematical statement.
> Many worlds is falsifiable, if you can show wave function collapse actually happens
So, what experiments do you think would falsify it? How can you show that collapse actually happened?
Showing collapse happened is really tricky because of decoherence. Similar to unmixing coffee and milk. But all systems we have observed so far do not show wave function collapse (granted these systems are generally small, but otherwise decoherence starts messing about).
These are just fundamentally different theories. Not just an interpretation, physically different outcomes.
In the Copenhagen interpretation, there is a difference between measuring a system and entangling with it. There exists a unitary that entangles you with the cat, just like there exists a unitary that entangles the cat with the quantum device. By definition, unitary evolution is not a measurement in the Copenhagen interpretation.
> Showing collapse happened is really tricky because of decoherence. Similar to unmixing coffee and milk.
Unmixing would show the lack of collapse (in the specific case), though? To show collapse you'd need somehow experimentally prove that it is impossible to unmix. And to falsify collapse, you'd need to somehow experimentally prove that it is always possible to unmix. And if we go with your analogy, would you say the coffee with milk hasn't forgotten its initial state because it is technically possible to unmix them? Being able to manipulate the whole universe's wavefunction to unentangle particular subsystems is akin to having access to Maxwell's daemon, since decoherence increases entropy.
In normal physics people often use occamz razor and subscribe to what the interpretation with the simplest postulates says.
So the reality is the opposite. You don’t like what the physics is saying so for emotional reasons you’ve come up with a completely new and novel framework to discount what the simplest set of equations is saying.
Nah, physics is not saying anything. I do physics because I enjoy discovering and modeling new phenomena. If someone wants to do philosophy and ask questions like "but what is __really__ happening when we measure an atom", it's his business, but I don't believe we'd be doing the same thing, because these questions are impossible to answer with empirical evidence and don't help us model reality in any way. I don't see any difference between QM interpretations; one of them might be "true"
Just like the AI nerds and the AGI singularity or Musk saying we are in simulation...
ie so many crazy ideas.. for the rationalist, its like being in an insane asylum and trusting one mental patient or another..
I suppose at some level its just not rational why we exist. We must accept some wild, fundamental metaphysical assumption
Where in MWI do you believe the preferred unique macroscopic reality is defined?
My interpretation of the interpretation is that the universe is a giant constraint resolution system. Particles are free to be anywhere randomly as long as they do not randomly interact with other particles. As soon as they interact they have fewer "degrees of freedom", since now they interacted. When they interact with anything macroscopic they have no freedom left. Makes sense to me anyway.
- That humans can't be put into quantum superpositions
- That a human being in a quantum superposition of two states A and B would feel at all to that human like being in a quantum superposition of two states A and B, when neither of those states is "a human feeling like they're in a superposition of two states A and B".
"Doc, I feel pain in my toe."
"No, sorry, the math says you don't."
"Okay, but like... I do."
"Sorry, you're just not good at accepting math!"
Not a perfect analogy, of course, but people have competing intuitions of what to do when the map fails to match the territory. MWI abandons the latter, most prefer the former.
The problem is that this is not what Schrodinger predicts, though. If |alive> and |dead> are valid solutions to the Schrodinger equation of some system, then so is any linear combination of them whose norm is one, such as 1/sqrt(2) |alive> + 1/sqrt(2) |dead>. So the math of QM predicts that there should be infinitely many cats that should feel partly alive and partly dead, many times more than the one live cat and the one dead cat. And yet you don't find this in any classical experiment.
1/sqrt(2) |alive> + 1/sqrt(2) |dead> is a valid solution to the Schrodinger equation. That cat is half alive and half dead.
That is different than |A cat that feels half alive and half dead>, which is its own completely different state. For a cat to feel like it is half alive and dead, or to notice that it is half alive and half dead, there are distinct things that happening in its brain that don't happen in either the |alive> or |dead> basis vectors, let alone any linear combination of the two.
We could even put all those states in a superposition!
1/sqrt(3) |alive> + 1/sqrt(3) |dead> + 1/sqrt(3) |half alive and half dead>.
So how did the classical world arise? Or how come we happen to be in the classical world, when there are infinitely many other non-classical observers? And note that the anthropic principle doesn't help here - all of the real laws of physics are the same for those other observers, you get the same chemistry etc, it's just the classical approximations that fail.
Many worlds isn't falsifiable, either. There's no reason to accept one over the other.
The Copenhagen wavefunction collapse is unfalsifiable.
I think these lectures are a good intro to QM. This statement feels very emotional though. Many-worlds just states there is no such thing as wave function collapse. The many worlds are a logical conclusion following. Copenhagen simply refuses to elaborate to when wave-function collapse happens, which to me is not a complete theory.
You could have some critique of many-worlds in relation to statistics, although I think many people have given quite satisfactory explanations.
Many worlds is just bare bones QM.. If any other theory is proposed, it should be falsifiable (like pilot wave theory for example). Doesn't mean it won't be difficult to measure.