> On 31 Jan 2021, at 06:48, Alan Grayson <[email protected]> wrote: > > When a particle hits the screen in a double slit experiment, is that a > measurement? AG
You can say that it is a measurement from the screen point of view. But as screen have no re-accessible memory, it is better to define the measurement relatively to some machine with Memory, like Everett. Bruno > > On Saturday, January 30, 2021 at 6:26:20 PM UTC-7 Alan Grayson wrote: > More Trump physics? What's a measurement? I have no clue. AG > > On Saturday, January 30, 2021 at 4:27:00 AM UTC-7 [email protected] > <applewebdata://68D57329-2B60-4CF9-8729-1DDC896C71A9> wrote: > On Fri, Jan 29, 2021 at 7:42 PM Bruce Kellett <[email protected] <>> 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, 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", 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. > > 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 [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/d015390b-6080-4a85-b960-f1d889ff4383n%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/d015390b-6080-4a85-b960-f1d889ff4383n%40googlegroups.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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/3796B92F-906A-41BA-A5C3-D8D0FA1728CC%40ulb.ac.be.
