On 25 May 2015, at 23:59, meekerdb wrote:
On 5/25/2015 9:31 AM, Bruno Marchal wrote:
On 25 May 2015, at 03:27, meekerdb wrote:
On 5/24/2015 5:05 AM, Pierz wrote:
On Sunday, May 24, 2015 at 4:02:42 PM UTC+10, Brent wrote:
On 5/23/2015 9:58 PM, Pierz wrote:
On Saturday, May 23, 2015 at 8:36:40 PM UTC+10, Liz R wrote:
I'm not sure why comp would predict that physical laws are
invariant for all observers. I can see that it would lead to a
sort of super-anthropic-selection effect, but surely all
possible observers should exist somewhere in arithmetic,
including ones who observe different physics (that is compatible
with their existence) ?
I really must dig up the old thread! But I'm not saying comp
does entail invariant physics for all observers, just that if
there are different physics, the substitution level must be very
low indeed. Think of the original scenario in the UDA: a person
in Washington is suddenly annihilated, and then duplicated in
Helsinki and Moscow (or whatever). That operation creates a 50%
probability of finding oneself in Helsinki or Moscow. But the
ultimate point of the UDA is that one's actual probability of
finding oneself in Helsinki or Washington depends on the total
measure of all virtual environments within which that observer
is instantiated in an environment that looks like one of those
cities. One can't isolate a particular
virtual system from the trace of the UD. So you can't create an
arbitrary physics in an environment that looks like either city
(or anywhere). Well you can, but any observer will always find
their own physics to be the measure of *all* their continuations
in arithmetic. So there can't be an environment that is like
Helsinki or Moscow at some point but that has different physical
laws. Carry this logic over to the scenario of a person standing
in an empty room - the physics the person experiences will be
the measure of all such identical persons standing in empty rooms.
"Experiencing physics" I think needs some explication. If
experiencing only refers to consciously thinking propositions,
then one may not be experiencing much physics: the world seems 3D
with colors, there's a mild temperature, air
smells OK,... One doesn't directly,
consciously experience the 2nd law, or the Born rule. The "laws
of physics" are human inventions to describe and predict events.
They're not out there in Nature; which is why we have to revise
them from time to time as we find more comprehensive, more
accurate "laws".
OK, but it doesn't seem relevant to the argument. We experience a
world predictable and stable in certain ways that, now we're so
sophisticated, we formalise into the science of physics. Bruno's
claim is that these regularities are not intrinsic properties of
some primary stuff, but emergent from the computational
properties of observers - namely how often various continuations
of those observers crop up relatively to one another in the
abstract space of all possible continuations. I'm trying to make
an admittedly difficult point about whether or not observers in
different places can experience different physics within this
paradigm, and if so, how that relates to "substitution level". If
you're worried about people "experiencing physics" let's just
concentrate on observers who go to the trouble of doing physics
experiments. It really doesn't matter.
My point was that most people's conscious experience most of the
time could be accommodated within a large range of physics. For
example Newtonian physics seems intuitive while quantum mechanics
isn't; but we think QM is the better theory. But Bruno claims
that his theory implies QM and not Newtonian mechanics. So if
people consciously experienced a Newtonian universe
(which they once thought they did) would that falsify comp or
would it just imply that the UD can instantiate Newtonian universes.
Which it can't. So, a Newtonian universe would have refute comp,
and indeed even locality as the Newtonian universe is not local.
But of course, a computationalist could say, that the "newtonian
character is illusory, and that by looking closer we will
discover ... something like QM.
So you are claiming that it would be impossible to have a conscious
being that experienced a Newtonian universe - that this would
produce a logical contradiction?
With comp, yes. Precisely, it would refute comp or indicate that you
belong to a simulation or a video game, build in the normal (quantum-
like) reality. Yes, that is all the UDA point.
Bruno
Brent
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