On Mon, Jun 28, 2021 at 7:46 PM Bruce Kellett <[email protected]> wrote:
*> I think John's trouble here is that he still adheres to David Deutsch's > concept of worlds. Deutch talks as though every component of a > superposition is a separate world. This leaves Deutsch no language to talk > about decohered worlds, pointer states, and all the other usual apparatus > of quantum interpretations.* > Not so, "superposition" is just a word that means a collection of particles that exist in very different physical states at exactly the same time, in other words it's a word that people like to use when they just don't want to say that the universe has split. In Many Worlds if the mathematics says that 2 things could happen then 2 things do happen. Usually when a universe splits the two never recombine again, that's why we usually don't see weird quantum effects in our everyday lives, and that's why making a Quantum Computer is hard. But If the difference between universes is very very small then a skilled experimenter can make them become identical again and recombine, and that produces interference. However the difference between the universes rapidly grows larger and the task of making them identical again rapidly becomes more difficult, so when the difference becomes larger than the microscopic level the possibility of them becoming identical again becomes ridiculously small, like in classical physics and the possibility that by pure random chance all the air molecules in the room you're in right now will go to the other side of the room and you'll suffocate to death. That's why you never see somebody as large as a human being use quantum tunneling to walk through a brick wall even though such a thing is theoretically possible. We don't always see a superposition of states, in fact usually we don't. If you flip a coin and it comes out heads then you are NOT living in the world where it came out tails. In a roughly similar way if you do the two slit experiment and see that the photon goes through slit A then you are not living in the world where the photon went through slot B. But the 2 slit experiment can be a little different from the simple coin toss example. If after the universe splits and the photon goes through both slits they then hits a photographic plate (or a brick wall) then both photons in both universes are destroyed and thus there is no longer any difference between the two, so the universes will merge back together. Then and only then you will see evidence that the photon went through both slits (aka. Interference) on the photographic plate even if you send the photos through one at a time. If you got rid of the film (or the brick wall) and let the photon head out into infinite space after it passes the slits then the two universes will never recombine, and so of course you will never see a interference effect. The beautiful part of the theory is that it doesn't have to explain what an observer is and that's why a brick wall will work just as well as a photographic plate. A measurement, if for some reason you'd like to use that word, is a change made in the universe, and it doesn't matter if that change is made in a conscious being or not. In one universe the photon hits the screen at point X, and in another universe the photon hits the screen at point Y, and in yet another universe the photon doesn't hit the screen at all because it doesn't pass through either slit. If there happens to be an observer watching all this he splits too, and they all have different memories about what happened. And it doesn't matter if nobody is watching, the universe splits anyway. In Many Worlds if you like you could replace the word "measurement" with the word "change" and you don't need to use the word "observer" at all, so you don't need to ponder the question of if a cockroach can observe things and make the universe split. John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> v42 -- 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/CAJPayv0qzCfPzMkNH3w-U_DOx3xN4EZZ%2BDLAdG8pJ_%2B64wXs-A%40mail.gmail.com.
