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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