On Thu, Aug 2, 2018 at 12:38 AM Brent Meeker <[email protected]> wrote:
> > > On 8/1/2018 10:22 PM, Jason Resch wrote: > > > > On Wed, Aug 1, 2018 at 11:34 PM Brent Meeker <[email protected]> wrote: > >> >> >> On 8/1/2018 3:46 PM, Jason Resch wrote: >> >> >> >> On Wed, Aug 1, 2018 at 1:39 PM Brent Meeker <[email protected]> wrote: >> >>> >>> >>> On 8/1/2018 3:51 AM, Bruno Marchal wrote: >>> >>> >>> On 31 Jul 2018, at 21:46, Brent Meeker <[email protected]> wrote: >>> >>> >>> >>> On 7/31/2018 9:11 AM, Bruno Marchal wrote: >>> >>> >>> On 30 Jul 2018, at 22:27, Brent Meeker <[email protected]> wrote: >>> >>> >>> >>> On 7/30/2018 9:58 AM, John Clark wrote: >>> >>> >>>> > >>>> *Forget collapse.* >>> >>> Many, perhaps most, physicists do exactly that because they believe in >>> the "Shut Up And Calculate" quantum interpretation and are only interested >>> in predicting how far to the right a indicator needle on a meter moves in a >>> particular experiment. But for some of us that feels unsatisfying and would >>> like to have a deeper understanding about what's going on at the quantum >>> level and wonder why there is nothing in the mathematics that says anything >>> about a wave collapsing. >>> >>> >>> That's not true. "The mathematics" originally included the Born rule as >>> part of the axiomatic structure of QM. >>> >>> >>> In the usual QM, yes. But this use a vague notion of observer, and a >>> seemingly forbidden process, a projection (a Kestrel!), I mean forbidden if >>> we apply the wave to the couple observer-particle. >>> >>> >>> >>> >>> Most of all they want to know what exactly is a "measurement" and why it >>> so mysterious. >>> >>> >>> The problem with the Born rule was that its application was ambiguous: >>> >>> >>> Ah! Exactly. >>> >>> >>> >>> Where was the Heisenberg cut? Why was "the needle basis" preferred? But >>> decoherence theory has given answers (at least partially) to those >>> questions. Given those answers, one can just replace "collapse" with >>> "discard", i.e. discard all the predicted possible results except the one >>> observed. Is there really any difference between saying those other >>> predictions of the wf are in orthogonal, inaccessible "worlds" and saying >>> they just didn't happen. That seems to be Omnes approach. He writes, >>> "Quantum mechanics is a probabilistic theory, so it only predicts >>> probabilities.” >>> >>> >>> >>> OK, but the honest, and perhaps naive inquirer would like to have an >>> idea about what are those probabilities about, and where they come from. >>> >>> >>> That was the source of resistance to Born's paper. Physicists assumed >>> that probability could only arise from ignorance of an ensemble. Since >>> there was no ensemble in Heisenberg's (or Schroedinger's) QM they resisted >>> the idea. Lots of attempts were made to reintroduce ensembles, or at least >>> virtual ensembles, so that they could feel comfortable with having a >>> probabilistic theory. Omnes' is just saying "Get over it!"; probabilities >>> are fundamental. >>> >>> >>> >>> Yes, but he said all this after defending Everett (or its own better >>> version of Everett). Then, this introduces a notion of ensemble (the set of >>> all consistent histories), and, at least in some book, just ask us to be >>> irrational and to dismiss the ensemble at make probability fundamental, >>> only to make the “other worlds” disappear. In one book he lakes clear that >>> such a decision is irrational, and that he makes it because he dislike of >>> find shocking the idea that all quantum possible outcome are realised. It >>> is a bit like a christian who understand the evolution theory, but add that >>> it makes just God having invented evolution instead of Adam. >>> >>> >>> >>> There's nothing irrational about discarding that which is not observed >>> and keeping that which is observed. >>> >> >> It is irrational if it results in a significantly more complex, ad hoc, >> or nonsensical theory. >> >> >> So it's irrational if it postulates infinitely many unobservable worlds. >> Nothing is more sensible than discarding that which is unobservable. >> >> See, I can be just as snarky as you. >> > > > I was being serious. This explains my position well: > https://www.scientificamerican.com/article/multiverse-the-case-for-parallel-universe/ > > Remember: Parallel universes are not a theory—they are predictions of > certain theories. > > To me, the key point is that if theories are scientific, then it's > legitimate science to work out and discuss all their consequences even if > they involve unobservable entities. For a theory to be falsifiable, we need > not be able to observe and test all its predictions, merely at least one of > them. My answer to (4) is therefore that what's scientifically testable are > our mathematical theories, not necessarily their implications, and that > this is quite OK. For example, because Einstein's theory of general > relativity has successfully predicted many things that we can observe, we > also take seriously its predictions for things we cannot observe, e.g., > what happens inside black holes. > Likewise, if we're impressed by the successful predictions of inflation or > quantum mechanics so far, then we need to take seriously also their other > predictions, including the Level I and Level III multiverse. George even > mentions the possibility that eternal inflation may one day be ruled out—to > me, this is simply an argument that eternal inflation is a scientific > theory. > > [...] > > George also mentions that multiverses may fall foul of Occam's razor by > introducing unnecessary complications. As a theoretical physicist, I judge > the elegance and simplicity of a theory not by its ontology, but by the > elegance and simplicity of its mathematical equations—and it's quite > striking to me that the mathematically simplest theories tend to give us > multiverses. It's proven remarkably hard to write down a theory which > produces exactly the universe we see and nothing more. > > The theory that branches we don't observe don't exist is a needless > complication to the simplicity of QM, one not motivated by evidence, > > > LOL! It's absence from all observation is not evidence motivating it's > non-existence. The inclusion of infinitely many unobservable worlds is > "avoiding a needless complication". I'm sorry but you have not convinced > me you are serious. > > Occam is about simplicity of assumptions, simplicity of theories, not simplicities of ontologies. It is a simpler theory that stars are distant suns, despite the fact that such a theory entails the belief in vast numbers (perhaps infinite) other star systems. It seems to me, in a different age, you would be the one arguing that stars are not distant suns, because it would make reality too big and complex. > and introduces all kinds of unintended baggage (priviledged reference > frames, magical observers, discontinuity, violations of unitarity, FTL > effects, perhaps even solipsism). > > > All invented and avoidable "flaws" which only in your mind are worse than > infinitely many worlds whose origin cannot be pinned down but we are > assured must exist because otherwise...horrors, non-unitarity might > obtain...and observation might be respected. > > Brent > > I think your issue is what Tegmark describes as the Omnivision observer, which you seem to assume: 1) Omnivision assumption: physical reality must be such that at least one observer can in principle observe all of it. I find no motivation for the omnivision assumption, and actually can find plenty of reason to doubt it. Jason -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
