On 31 Dec 2017, at 19:50, 'scerir' via Everything List wrote:
Il 31 dicembre 2017 alle 17.51 Bruno Marchal <marc...@ulb.ac.be> ha
scritto:
On 28 Dec 2017, at 08:50, 'scerir' via Everything List wrote:
>
Il 27 dicembre 2017 alle 23.24 Brent Meeker <meeke...@verizon.net>
ha scritto:
So you think Bruno's theory fails because spacetime is discrete?
According to Deutsch "Every finitely realizable physical system can
be perfectly simulated by a universal model computing machine
operating by finite means." (It is the Church-Turing-Deutsch
principle, I guess).
Not at all. The computability notion of Church, Turing does not rely
on anything physical. You can define the notion of universal machine
in pure number theory.
Deutsch thesis is a completely different thesis, and to relate them
needs to understand first how physics emerge from numbers, or to
invoke some deity.
I'm not so familiar with the Church-Turing-Deutsch principle and the
different meanings (or conceptual roots) of this principle. I must
re-read something.
http://michaelnielsen.org/blog/interesting-problems-the-church-turing-deutsch-principle/
https://www.cs.princeton.edu/courses/archive/fall04/cos576/papers/deutsch85.pdf
https://philpapers.org/rec/DEUPPA
https://link.springer.com/article/10.1007/BF01886521
Whether space-time is a finitely realizable physical system franklyI
do not know. Feynman wrote "It always bothers me that according to
the laws as we understand them today, it takes a computing machine
an infinite number of logical operations to figure out what goes on
in no matter how tiny a region of space, and no matter how tiny a
region of time. How can all that be going on in that tiny space? Why
should it take an infinite amount of logic to figure out what one
tiny piece of space/time is going to do? So I have often made the
hypothesis ultimately physics will not require a mathematical
statement, that in the end the machinery will be revealed and the
laws will turn out to be simple, like the chequer board with all its
apparent complexities. But this is just speculation." (The Character
of Physical Law - Ch. 2)
You assume a metaphysical physical reality. With computationalism,
that is quite premature. There are no evidence, and it makes the mind-
body problem insoluble in any weak mechanist theory.
Then the universal machine offers a solution on a plate already, and
we can test it.
Bruno
Yes, I still assume physical reality, and (quantum) systems as
carriers of finite quantities of informations (yes, information is a
difficult concept, especially in strange situations like
entanglement swapping, and the like) . I may be wrong, of course.
You might be right, also. But then the computationalist theory of mind
is false. The evidences side more with mechanism, but without the
evidence for the quantum reality, I would plausibly think that
Mechanism is not really plausible. It is really Gödel + the empirical
quantum reality which confirms Mecahnism, and this in its most
startling aspects. But my point is that this is testable. If primary
matter exists, we will know it.
Bruno
s.
>
However, gamma ray propagation from distant supernova show no
dispersion, which implies that spacetime is smooth to severl orders
of
magnitude below the Planck scale.
But either way the physics a cannot be compared to Bruno's theory
because his theory makes not definite prediction even about the
existence of spacetime.
Brent
On 12/27/2017 1:22 PM, 'scerir' via Everything List wrote:
Brent wrote:
A good idea, but I don't see that these "predictions" of
computationalism have actually been derived. I think most of them
are aspirational. For example, what is the proof that spacetime is
continuous - in fact what is the proof there is such a thing as
spacetime?
--------
Actually Einstein wrote: "reality cannot at all be represented by
a continuous field." (The Meaning of Relativity, Princeton Science
Library, 1988, p. 160). In a letter to Hans Walter Dällenbach
(1916) Einstein also wrote: “But you have correctly grasped the
drawback that the continuum brings. If the molecular view of
matter is the correct (appropriate) one, i.e., if a part of the
universe is to be represented by a finite number of moving points,
then the continuum of the present theory contains too great a
manifold of possibilities. I also believe that this too great is
responsible for the fact that our present means of description
miscarry with the quantum theory. The problem seems to me how one
can formulate statements about a discontinuum without calling upon
a continuum (space-time) as an aid; the latter should be banned
from the theory as a supplementary construction not justified by
the essence of the problem, which corresponds to nothing “real”.
But we still lack the mathematical structure unfortunately. How
much have I already plagued myself in this way!”.
See also http://holometer.fnal.gov/
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