The Emergent Multiverse - The Many-Worlds Interpretation
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- Опубликовано: 31 июл 2024
- Professor David Wallace delivers two talks on the Many-Worlds Interpretation of quantum mechanics. In the first lecture, he examines the justification for interpreting the superposition states as multiplicities, and in the second lecture, he asks how we make sense of probability in the Many-Worlds theory.
The Many-Worlds Interpretation (MWI) of quantum mechanics holds that quantum theory - our best current theory of physics - is correctly understood as claiming that there are many worlds that exist in parallel to our own and which branch constantly off our own. The existence of the other worlds makes it possible to make sense of physics without action-at-a-distance, objective randomness, or any strange role for an "observer" or "consciousness". During this weekend school, this interpretation of quantum mechanics is discussed and it is asked what would follow from its being the correct one.
These talks were given in 2014 as part of a series at Oxford.
00:00 The Plurality of Worlds
53:30 The Probability Puzzle
#Philosophy #Science
I'm thankful I live in an era where I can view these kinds of talks online for free. David spoke eloquently and made good arguments and, even if the strong argument regarding probabilities doesn't work, the weak argument is still a reasonable point. I think most scientists aren't committed to one interpretation over another, but it is certainly an important question as our philosophy of physics influences the way in which we may seek to improve our theories and discover new physics. While I'm uncertain that David is right, he is undoubtedly advancing progress in the topic in the long term simply by bringing the discussion to the attention of more people and encouraging critical thought, when at least the latter part of the 20th century seemed to be dominated by the "shut up and calculate" crowd.
Or... you could read Everett's thesis and then you would notice that his second sentence is already wrong. His argument never recovers from that mistake. ;-)
A HUGE fan of Dr. Wallace! Thank you for the great lectures.
Bro took 10^21 sips of water
Great set of lectures!
referring to Schrodinger's Cat, experiment would have to be done more than 9 times, just to be sure.
Well, I’m not sure that would be enough. There would be many future experimenters on the branches where the cat died less than 9 times. In fact, most of them. Only on a fraction 1/512 branches would you see a 9 times dead cat.
So you’d have to repeat this process for many cats to get solid empirical results.
If we want a chance to kill the cat given that we’re assuming the theory well then what you’re suggesting is enough.
😂😂😂❤
When listening to these experiments I apply the idea of light intensity to the intensity of the light I use in thought imaging. Does anyone else do this?
The issues with probabilities in the Many Worlds interpretation are quite clear:
- Having e.g. two possible outcomes A & B with probability, say, 3/4 & 1/4 correspondingly, is straightforward for the standard interpretation of QM.
In MW it means that you have branches with different weights ( or " thickness " as Wallace says), but what is the *physical interpretation* of these weights? Some worlds are more real, so to speak than the others? What does that mean?
For a "frequentist" kind of interpretation it doesn't work either, unless we have infinite branches each time...
- And then you have the issue with the irreducible randomness that appears at the macroscopic level ( the " in which branch", or self-locating, or "self identity" uncertainty as various proponents of MW call it) that makes the Everettian QM a peculiar hybrid of determinism at the fundamental level of Ψ, and probabilism / stochasticity at the ( strongly?) emergent, macro level...
Schrodinger''s cat is not alive and dead at the same time.
1:30:56 There are no " double standards" or criteria, because in the other interpretations of QM ( except Qbism and the MWI) probabilities are fundamental and irreducible in a consistent way.
In the Deutsch/ Wallace " subjective derivation" ( decision theoretical), you need to define / assume observers at the macroscopic emergent level ( and these observers need to be described by the same laws of QM as everything else, so you have the same circularity issue as in the old Copenhagen + extra baggage!).
- Moreover, the Wavefunction is evolving deterministically, but the self identity uncertainty - the "in which branch" randomness - cannot be deduced in a reductionist way from the Schrödinger equation!
So, actually, the other interpretations are consistent ( about Probabilities) while MWI is not!
The self locating uncertainty isn't really an additional assumption to the Schrödinger equation. It is the only possible way observers within a multiverse can experience their timeline when you assume that different branches evolve independently. This latter fact in turn is also a consequence of the Schrödinger equation and not really an assumption.
@@MrBajaJunky The existence of "sentient observers" is necessary for decision theoretic ( Deutsch / Wallace) or "subjective" ( Carroll) derivations of the QM Probabilistic rule.
It's an issue very similar to Qbism, where it is assumed that "conscious agents" are primary. That is a circular dead end, because what they assume as "primary" is actually an "emergent" property, that has to be described by the same fundamental laws as everything else.
- As for the "self-location/ identity uncertainty", that's a more subtle issue:
Before doing a "measurement", I don't know "in which branch" I'll find myself afterwards, *in principle* ( there are no hidden variables in MW, or any other "secret mechanisms").
So, this randomness, although it appears only at the macro level, it's irreducible ( in principle), it cannot be deduced by the Schrödinger equation, so it's also fundamental in that sense.. ( Note that *my perception* about that randomly chosen emergent world in which I'll find myself afterwards is a physical property, a function of my brain/ nervous system).
Moreover, there's no clear"dividing line" where this irreducible stochasticity ( about the self- identity) appears!
Decoherence helps ( in practice), but it's only FAPP, not fundamental as this randomness is...
So, in MWI we have the same subjective, "epistemic collapse" of the wavefunction in each individual branch as in the standard Copenhagen interpretation.
The basic difference is that MW is a hybrid theory ( deterministic / Probabilistic) while the standard version is fundamentally probabilistic all the way.
The main issue for both is that Probabilities are irreducible and they appear at the macroscopic level.
So, the basic mystery ( for all interpretations) is the "strong emergence" of classicality, as we perceive it.
Thank you for this explanation, I have been learning about the probability objection to many worlds, and this is one of the best concise summaries I've seen of it. It does strike me that there is a strong similarity (almost a complimentarity if you will) between many worlds and Copenhagen in relation to epistemology.
In Copenhagen, the observer needs to collapse the many possibilities down to one actual result, while in many worlds, there are many actual results, and we need to determine which of these is perceived by an observer. It seems that it's impossible to avoid some form of mind body dualism on the many worlds account if you want to stick to our tried and true ideas about scientific method. Otherwise, you would have to say that every quantum result of an experiment is actually observed, since, according to MWI, there is an observer on each branch who witnesses the result.
This comment section is nauseating. I would pay for access to your channel, if that would help filter out the fools.
Everybody who talks about MWI is a fool, which includes the speaker. ;-)
@@schmetterling4477 “Who is more foolish? The fool or the fool who follows him?”
@@platinumfalconm3891 I didn't watch the video. As soon as "MWI" pops up I mark it as bullshit. ;-)
What's up with all the peanut gallery comments?
Mention Quantum physics seems to bring out all the weirdos and wing nuts.
@@StephenYuan Same thing with philosophy of mind, to a lesser degree.
These are some of the most inane comments I’ve ever seen on RUclips.
…
On RUclips.
It seems like there's a few comments, including this one, which don't contribute to the discussion of ideas, while there are also several that are engaged with the intellectual issues raised by this. There's always a mix of good and bad comments, but compared to many parts of the internet, the discussion here is relatively high quality in my opinion.
Tiger analogy is ridiculous
No, it's not
For the mystery of iniquity doth already work: only he who now letteth will let , until he be taken out of the way.
2 Thessalonians 2:7 KJV
more like THIS!... come on, P.O.... up yo game, mang!!!... and language game will consume most copiously muchly... you know this!!!!!!!!!
😂 sounds like non-sense.
So are you more of a Copenhagen Interpretation guy, or do you just post laughter emojis about subjects you have no idea about in hopes people will give you up-votes? Daniel Everett's position is something more theoretical physicists are interested in considering nowadays.
@@neilmacdonald6637: "Daniel Everett"?🤔 Wasn't the guy's name Hugh Everett?
@@rv706 Daniel Everrett is Hugh's brother in a parallel universe.
Try to keep up brother.
This is likely the most atrocious lecture I have ever viewed.
Is it also the first?
On what basis do you say this?
@@pectenmaximus231 well, to begin, I suppose one should identify his mischaracterisation of Occam, for Occam never even utilised the terminology of plurality of entities (“Occam’s Razor”) within any of his known text (such as his philosophical writings or his “Theory of Terms”). Rather this “structuring” of of symbols was first acknowledged, in this respect, by Froidmont over two centuries succeeding Occam’s death along with John Punch nearly three centuries proceeding the death of Occam. Furthermore, Occam oftentimes within his texts posited that symbols are not fully (I state “not fully” here as Occam adhered to the notion of a “Mixed Bivalence” in which their is a “definite” and “indefinite” truth as he has alluded to within his philosophical writings, but this is to state that truth is only of one restricted sense or of another, but this to make a deviating sense of the matter and to recognise something different as a whole (divergent matters of expression, for example), thus it does not bear any imposing feature at all). The fact that there is no single interpretation on this matter (like any other) should be an indication that “Occam’s Razor” is not a foundation of method or a particular parameter of observation, for one must have supposition to begin with in order to uphold this view, so it must be something quite different as it is (of course) not an isolated matter (for isolation would lose its sense in this case, but this is rather vacuous to state).
@@pectenmaximus231 Additionally, to hold the notion of a “multiverse” is quite myopic, for it involves a postulation that matter is restricted, but in what sense is matter relinquished to this or that thing? From this one goes on to name certain aforementioned things or instances, but this only shews (in this respect) that matter does not treat of anything (so to speak) and so upholding a notion primitive ideas of matter cannot do for this task in the way the person issuing this lecture is attempting to allude to. If matter is restricted, in what way? How? Again, as stated above, the fact that this must be expounded upon is a telling feature that notions of matter are not of one restricted sort (and perhaps even concrete, at times) or of another.
@@Prodigushereditas Wallace himself points out in an aside that "Occam's Razor" is not directly mentioned in the man's writings; its a principle abstracted from his writings by later interpreters.
Anyway this isn't a lecture on Occam's Razor but on the Many Worlds Interpretation of QP. Your comment is an off topic, pedantic footnote on an issue of interest only to certain intellectual historians.
The universe is an idea. A fixed number of many universes do not make a multi universe, but a universe again. Before giving lectures to yourself study the basics of logic.
You are getting stuck in terminology and you're missing the point(s) of the whole talk.
Sounds like someone is not knowing what he is talking about