He certainly deserves one for saying "It is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct." Pity about the rest.atyy said:That's alright. It's John Wheeler's fault. In comparison, Kaku deserves the Nobel.
I do not see why I need to do anything of the sort. It is a term in common use. If you either don't understand or have issues with it, you should refer to Everett.bhobba said:Now you are shifting your claim.
First you need to define what you mean by relative state.
Derek Potter said:I do not see why I need to do anything of the sort. It is a term in common use. If you either don't understand or have issues with it, you should refer to Everett.
This needed an answer before you got sidetracked into fleas and elephants.Swamp Thing said:Assume that a device with a pointer is located close to ONE of the paths. After propagating further over a really long distance and time, the wave packet reaches a detection zone. Just before this happens, we can decide to switch the experiment between a setting where the pointer reveals the path information, to one where it can't. Depending on this decision, we se or don't see interference.
Now, does it matter how "macroscopic" the pointer device is? If it is just an atom or something, then it's plausible that it could give back the energy or whatever that it exchanged with the photon, and no one any the wiser. On the other hand, let's say the device is a photomultiplier tube, and the cascade of electrons should have reached the point of no return long before the wavepacket could reach the detection zone. What then? Can you put the toothpaste back in the tube even at this point? Or should we say that the cascade would be triggered nonlocally - or not triggered at all - depending on the scenario that exists in the detection zone at the last femtosecond? Would it make a difference whether or not the coherence length spans the PMT and the detection zone?
Derek Potter said:Why do say "bandy about"? I am using the term correctly.
There is no assumption involved. The term "world" is fanciful and Everett did not like it, but to identify |a>|b> as a world is not an assumption, it is just a definition.bhobba said:Dear oh dear its obvious you won't define it. If you did you may see the error you are making wrt MW.
Here is the definition. Suppose two systems are entangled eg 1/root 2 |a>|b> + 1/root 2 |b>|a>. The systems are entangled hence neither has an actual state. If system 1 is observed in state |a> then system 2 will be in state |b>, and conversely, if system 1 is observed in state |b>, then system 2 will be in state |a>. State |a> is relative to state |b> and conversely.
Now your claim was 'MW is a principle which follows tautologically from the assumption of linear (quantum) evolution.'. In fact in Everett's original interpretation, without the modern use of decoherence, used the concept of relative state, and INTERPRETED the relative states as separate worlds ie |a>|b> was one world and |b>|a> another.
Its a key interpretive assumption - it does not follow tautologically because it requires that assumption - tautologies can't use extra things put into it - by definition a tautology is a circular statement.
Thanks
Bill
Derek Potter said:There is no assumption involved. The term "world" is fanciful and Everett did not like it, but to identify |a>|b> as a world is not an assumption, it is just a definition.
No confusion here, Bill. Rather than repeatedly insulting my intelligence I suggest you stick to the point and say what you think is the assumption.bhobba said:Derek -- you are a bit confused between definition and assumption - world in MW is much more than a definition.
Thanks
Bill
Derek Potter said:No confusion here, Bill. Rather than repeatedly insulting my intelligence I suggest you stick to the point and say what you think is the assumption.