>>> that doesn't mean you can't measure them both precisely
>> But thanks to Heisenberg's uncertainty principle you can't predict what that measurement will be, and even if you repeat conditions exactly you will not get the same measurements for momentum and position (or energy and time) if you perform the experiment again.
> Yes, exactly. But my point is that the fact that you can measure both precisely for the same particle is commonly denied. The problem in is that the HUP applies to an ideal measurement, one that leaves the system having the measured value, in other words a preparation.
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> Are there multiple worlds with zero probabilities?
On Fri, May 9, 2025 at 4:10 PM Brent Meeker <meeke...@gmail.com> wrote:
> Are there multiple worlds with zero probabilities?I can't answer that question until you answer a question of my own. Zero probability of what? And if your answer is "of being observed" then my next question is "being observed by who?"
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>>> Are there multiple worlds with zero probabilities?
>> I can't answer that question until you answer a question of my own. Zero probability of what? And if your answer is "of being observed" then my next question is "being observed by who?"
> No
> if you measure a variable A in a world it was just measure to have the eigenvalue Ao, then MWI says you are in a world with A=Ao with probability 1.0 Yet you wrote that "Many Worlds says it was in every state that is not forbidden by Schrodinger's Equation." The system is not forbidden by Schrodinger's equation to be in other states Ai; it is a contingent fact that it happened, in this world, to land in state Ao the first time it was measured. So it has probability zero of being a world where A=Ai.
> This has nothing to do with being observed or by whom
> unless you think consciousness is necessary for measurement.
On Fri, May 9, 2025 at 9:24 PM Brent Meeker <meeke...@gmail.com> wrote:
>>> Are there multiple worlds with zero probabilities?>> I can't answer that question until you answer a question of my own. Zero probability of what?
And if your answer is "of being observed" then my next question is "being observed by who?"> No
No? Neither of the two questions can be answered by a simple yes or no.
> if you measure a variable A in a world it was just measure to have the eigenvalue Ao, then MWI says you are in a world with A=Ao with probability 1.0 Yet you wrote that "Many Worlds says it was in every state that is not forbidden by Schrodinger's Equation." The system is not forbidden by Schrodinger's equation to be in other states Ai; it is a contingent fact that it happened, in this world, to land in state Ao the first time it was measured. So it has probability zero of being a world where A=Ai.The source of the massive confusion as seen in the above lies, as always, with the misuse of the personal pronoun "you",
> John K Clark is just obfuscating. Paraphrase the same thought as "If a variable A is measured in..."
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On Sat, May 10, 2025 at 3:15 PM Brent Meeker <meeke...@gmail.com> wrote:
> John K Clark is just obfuscating. Paraphrase the same thought as "If a variable A is measured in..."What a variable is measured in is not relevant, who is doing the measuring is. And in the context of a Many Worlds discussion "Brent Meeker will measure A" is NOT a paraphrase of "you will measure A" because the first statement makes sense but the second statement is gibberish.
itc
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On 5/10/2025 5:01 AM, John Clark wrote:
Obviously a zero probablity of having measured a value Ai =/= Ao.On Fri, May 9, 2025 at 9:24 PM Brent Meeker <meeke...@gmail.com> wrote:
>>> Are there multiple worlds with zero probabilities?>> I can't answer that question until you answer a question of my own. Zero probability of what?And if your answer is "of being observed" then my next question is "being observed by who?"> No
No? Neither of the two questions can be answered by a simple yes or no.
> if you measure a variable A in a world it was just measure to have the eigenvalue Ao, then MWI says you are in a world with A=Ao with probability 1.0 Yet you wrote that "Many Worlds says it was in every state that is not forbidden by Schrodinger's Equation." The system is not forbidden by Schrodinger's equation to be in other states Ai; it is a contingent fact that it happened, in this world, to land in state Ao the first time it was measured. So it has probability zero of being a world where A=Ai.The source of the massive confusion as seen in the above lies, as always, with the misuse of the personal pronoun "you",
John K Clark is just obfuscating. Paraphrase the same thought as "If a variable A is measured in..."
Brent
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> Why do you think it matters who makes the measurement?
> Results in all but one eigenvalue having zero probability in the MWI,
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>>> Results in all but one eigenvalue having zero probability in the MWI,
>>I ask again, a zero probability of exactly what?
> Of worlds with values of A other than Ao. Try to put a little effort into understanding, John.
John K Clark See what's on my new list at Extropolis
On Sat, May 10, 2025 at 5:39 PM Brent Meeker <meeke...@gmail.com> wrote:
>>> Results in all but one eigenvalue having zero probability in the MWI,
>>I ask again, a zero probability of exactly what?
> Of worlds with values of A other than Ao. Try to put a little effort into understanding, John.
This is getting silly. If Many Worlds is correct then there is NEVER a time or a place where the amplitude of the quantum wave collapses to exactly 1 and is zero everywhere else,
it's the very thing that makes it different from every other quantum theory. And neither Many Worlds nor any other theory can answer a question if the question makes no sense.skjJohn K Clark See what's on my new list at Extropolis
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If Many Worlds is correct then there is NEVER a time or a place where the amplitude of the quantum wave collapses to exactly 1 and is zero everywhere else.
> That's what Schroedinger's equation says if a measurement of A produces Ao and then A is immediately measured again.
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>> There is absolutely nothing in Schroedinger's equation that says the amplitude of the universal quantum wave collapses to exactly 1 and is zero everywhere else when a measurement is made, there isn't even anything in it that explains what a "measurement" is. The rule you mention was added on by the Copenhagen people, so according to them there are two separate rules of physics, one set of the laws of physics is for things that are not being observed, and the other set of the laws of physics are for things that are being observed. Many Worlds advocates say there is only one set of the laws of physics.
> And apparently that there is no such thing as a measurement leaving a system in an eigenstate of an observable. This is will come as a surprise to many experimentalist.
>> you are assuming that only the electron must obey Schrodinger's Equation, not the lab equipment needed to measure the electron, and most importantly not the experimentalist who is looking at the measuring device; they still follow classical physics. That clumsy poorly defined assumption was just tacked on by the Copenhagen people because they were frightened by the logical consequence of not doing so. That's why Many Worlds is barebone no-nonsense Quantum Mechanics that contains everything that is necessary and not one bit more. As Richard Feynman said “nature isn't classical, dammit".
> I made no such assumption. You're just making up objections. Are you asserting that a measurement does not leave a system in an eigenstate of the variable measured?
> This has nothing to do with being observed or by whom
Difficult, for me, to imagine how a measurement is performed in Alpha Centauri (according to MWI)
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> Difficult, for me, to imagine how a measurement is performed in Alpha Centauri (according to MWI)
John K Clark See what's on my new list at Extropolis
You are not the only Brent Meeker doing that exact same measurement! If Many Worlds is correct then there are an astronomical number (or an infinite number) of yous in a world where the observable variable A has just been measured. In one of them experimental results tell "you" there is a 100% probability that "you" are in the world where the value of variable A is X is exactly equal to 1. But there are many many more Brent Meekers in which their experimentation tells them that there is a 100% probability that variable A has a very different value than X. And all those Brent Meekers believe in Quantum Mechanics just as strongly as "you" do.> This has nothing to do with being observed or by whomIt most certainly does IF the question asked is "what will an experimenter observe?" And that was the fundamental question Brent Meeker asked.
3gv
Ok, but are observers in Alpha Centauri? And ... are there collapses (reductions of wave packets)?
> Ok, but are observers in Alpha Centauri?
John K Clark See what's on my new list at Extropolis
> the correctness of MWI is what is in question, so you're begging the question by assuming it's true.
> which is based on successive measures of the same variable. The second measurement has only one possible outcome contrary to you assertion that all values consistent with Schroedinger's equation must obtain
> You seem to have missed the point of the argument
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> My argument is with your statement that MWI means that all results consistent with Schroedinger's equation will occur, not with MWI. Some results have zero probability, which means they don't occur.
John K Clark See what's on my new list at Extropolis