> On 30 Jan 2021, at 12:26, John Clark <johnkcl...@gmail.com> wrote: > > On Fri, Jan 29, 2021 at 7:42 PM Bruce Kellett <bhkellet...@gmail.com > <mailto:bhkellet...@gmail.com>> wrote: > > > There is no requirement for an infinite number of degrees of freedom. > > In physics there will never be a theory that requires infinite degrees of > freedom, at least not until somebody performs an experiment with infinite > accuracy, and I'm not holding my breath for that. > > > Escape of just one IR photon to outer space is sufficient to destroy > > reversibility. > > Sometimes, usually in fact, but not always. Not if 2 quite different events > can produce the same identical photon that escapes into infinite space, and > not if the photon is not even allowed to escape but Is absorbed by a > photographic plate or a brick wall. A good example of this sort of thing > would be the quantum eraser experiment, or the delayed choice experiment. Or > just study how a Mach–Zehnder interferometer works. These experiments are > possible but they're not easy because the experimenter must make sure that > there's a difference between the two worlds but the difference must be very > small so a practical way can be found to make the two worlds identical again > so they can be nudged back together again into one world. > > > The definition of 'world' in the context of QM is made exact precisely > > because of this irreversibility. > > Only in pure mathematics are definitions precise,
Relatively to some axiomatic, but once a theory is rich enough to get elementary arithmetic (and/or the Turing universal machine) it will have an infinity of non isomorphic models, and this will shows that some definition are only precise enough for their use, but irremediably vague on their semantics… … unless we use second-order logic, but then the price is that the proof are not checkable, we most compactness (we can have all finite subset of a theory being consistent, yet the whole set of theorems get inconsistent (no model at all). Mathematics is less different than physics in this respect. After Gödel we know that all the infinities are unable to secure the finite realm. In fact “finite” itself is a term that we cannot “really” defined, and provably so if we add Mechanism, or just the Church-Turing hypothesis in the picture. > in science and and everything else they're just an approximation, a label for > an idea learned through examples, a collection of words that are defined by > other words. And Hugh Everett invented the theory but he didn't invent the > phrase "Many Worlds”, Actually he did, according to his daughter and son (according to a Russian who wrote a biography of Everett). It seems that he labels his theory “many-worlds” at the start, but was asked by the publisher of its first paper to replace it with “relative state”. I find this a bit sad, as “relative state” admit a mathematical definition, where “worlds” is just a metaphysical idea use in this context to avoid metaphysical question. > that was done by others and only gives a very approximate idea of what the > theory is about. According to Everett the debate on if matter is made of > particles or waves is over, it's made of waves. And in that theory the > approximate definition of the world "world" is a collection of different > waves that include at least one conscious being that is approximately the > same in all of them. > > > Worlds are well-defined > > Words are defined by other words and those words are in turn defined by yet > more words. Even the word "defined" is defined by words. But whatever > physical reality turns out to be at its most fundamental level I think we can > be pretty sure it's not made of words. That is why in mathematics and in (serious) metaphysics, we use the axiomatic method, where all words are either constant or variable, and have no other definition that the principle on which we agree. Here, mathematical logician are far more in advance that most scientist, who believe words have precise meaning, where the best we can hope for is “valid use”. But this requires a bit of mathematical logic, which is not well taught, when taught at all. Bruno > > John K Clark See my new list at Extropolis > <https://groups.google.com/g/extropolis> > > > -- > 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 everything-list+unsubscr...@googlegroups.com > <mailto:everything-list+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAJPayv0PC2xCLVb-TqzR2nHYoLzfzNekmRVht8RNqi_UGyWw8w%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAJPayv0PC2xCLVb-TqzR2nHYoLzfzNekmRVht8RNqi_UGyWw8w%40mail.gmail.com?utm_medium=email&utm_source=footer>. -- 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/ED98851D-ED7C-4A02-B44B-ED5C77A8525D%40ulb.ac.be.
