On 09 Jun 2015, at 07:24, Bruce Kellett wrote:

LizR wrote:
What comp - or any theory of physics - has to show is that observers will experience the passage of time. SR for example posits a block universe, which at first sight might not seem to allow for us to experience time. But of course it does, even though the whole 4D structure is "already there" in some sense.

The block universe idea is just a picturesque way of describing the way space and time are 'mixed up' (within the bounds of the light cone) by Lorentz transformations in special relativity. As I have said before, the important feature of the SR structure is that there is an absolute separation between spacelike and timelike surfaces or world lines. The subjective experience of time is not part of the relativistic model -- time is given by the behaviour of clocks, and specifically, clocks are physical systems that obey the laws of physics. The oscillations of certain defined transitions in the caesium atom are used to define the standard for physical time.

Not because we "crawl up world-lines" as Weyl poetically put it, but because each moment along our world-line contains a capsule memory of earlier moments, but not later ones.

The 'time capsule' idea is a recent proposal by Julian Barbour. Special relativity says nothing about such things. SR is, in fact, completely indifferent to the direction of time -- the equations are time symmetric.

(The later ones are just as "already there" as the earlier ones, according to the theory, but the laws of physics are structured in a way that means they aren't accessible.) Similarly, comp needs to show that "observer moments" will contain memories of other observer moments, but only those that existed earlier in the sequences of computations that gave rise to the current moment. This isn't physical time, whatever that is, but it does involve that certain laws apply to computation.

Well, maybe comp can do this, but it seems to me that it is more important to extract the behaviour of caesium atoms (physical clocks). The 1p experience of time comes from the fact that we are physical creatures embedded in a physical world that has a well- defined concept of time, given in terms of dynamical physical processes. Either comp can give this, or comp is totally useless.


Comp is just the statement that there is no magic operating in the brain. If you have a different theory of mind, please give it to us. What, in the brain, would be not Turing emulable. Matter? Then we agree, but you need to abandon all known theory of matter, except the collapse of the wave, which does not make sense to me. But my point was not more than that: comp entails a MWI, and we can test it by comparing it with the "MWI" of nature.



The 1p experience has to relate to intersubjective agreement (the 3p picture), or it cannot reproduce physics.

Of course.




None of this is known, or proven, of course, but the concept is well understood (as fro example in "October the First is too Late")

You should not get your physics from science fiction stories -- they are seldom a reliable source.

The validity of a reasoning does not depend on the paper on which it is written.

Bruno




Bruce

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