On Mon, May 29, 2017 at 2:26 PM, Bruce Kellett
<bhkell...@optusnet.com.au> wrote:
> On 29/05/2017 6:26 pm, Telmo Menezes wrote:
>>
>> On Mon, May 29, 2017 at 3:26 AM, Bruce Kellett
>> <bhkell...@optusnet.com.au> wrote:
>>>
>>> On 29/05/2017 9:45 am, Pierz wrote:
>>>
>>> WRT to this whole multi-coloured T-Rex business, there is a simpler point
>>> to
>>> be made. My original argument was in favour of MWI. Now whether, in MWI,
>>> macroscopic histories can merge is surely an interesting puzzle. But
>>> without
>>> MWI, there cannot be any ambiguity about the colour of T-Rexes. In a
>>> single
>>> universe interpretation of QM, T-Rexes were blue or they were red and
>>> they
>>> can't exist in a superposition of both. The past can't turn back into a
>>> mush
>>> of probabilities, because that would imply either that there is some "3p"
>>> significance to the concept of "now", or that the past consists of many
>>> worlds. In other words I am asserting that, sans MWI, any ambiguity about
>>> the past is a matter of ignorance, not of quantum uncertainty. Otherwise
>>> you
>>> are saying that past moments which once were well defined are somehow
>>> dissolved back into ambiguity by the passage of time. But that would be
>>> privileging the now with some kind of absolute significance, which is
>>> untenable. All nows are equal.
>>>
>>> Another way of stating my argument is that the following three
>>> propositions
>>> are mutually incompatible:
>>>
>>> There is a single history
>>> There is no objective significance to the concept of the current moment
>>> ("now")
>>> The future is objectively uncertain
>>>
>>> You can take your pick which of those propositions you reject, but it's
>>> logically impossible to support all three.
>>>
>>>
>>> I would say that there is only one history leading to our present state.
>>> Whether you take an MWI view or a collapse view, the wave function
>>> branches
>>> deterministically at every point, so if you follow your current twig back
>>> down to the main trunk etc, there will be a unique path.
>>
>> I don't think we can say we are in a specific twig. Many things about
>> out present state are unknown/undefined. I can imagine that there are
>> many well-defined present states that are compatible with my current
>> subjective state.
>
>
> Sure, but we are talking about wave functions, not subjective states.Replace "subjective" with "incomplete knowledge". >> In fact you can perform a quantum erasure experiment, and be sure that >> your current state goes through at least two different shortest paths >> to the root, and it becomes nonsensical to say that one is the >> "correct" one. I don't think anyone knows how far this can go into the >> macroscopic world, but I don't see any reason to believe that it >> doesn't. > > > I don't understand what you think you are getting in a quantum erasure > experiment. If the "which way" information that was gathered is erased, > normal interference patterns are seen in the double slit situation. The two > paths (through the separate slits) are in unresolved superposition until > they hit the detector, when decoherence takes over. There are not two > separate worlds, and your state is the result of the superposed paths, not > of either path separately. There is no ambiguity about which the the > "correct" path -- neither is, both contribute equally. I would say that the delayed choice version of the experiment makes it clear that there are two possible pasts that lead to the same present state -- they differ by one bit of information. > Bruce > > > -- > 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 post to this group, send email to everything-list@googlegroups.com. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. -- 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 post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
