On 03 Feb 2014, at 00:35, LizR wrote:
On 3 February 2014 08:03, meekerdb <[email protected]> wrote:
On 2/2/2014 1:44 AM, LizR wrote:
Someone asked how a block universe "comes to exist" and if it comes
into existence "all at once, or a bit at a time" (or something like
that).
I wish I could find the original question, to make sure exactly
what it was. But I haven't managed to find it, and I can't spend
all night trawling the forum for it, so I will just put my take on
the matter here.
Assuming I've got it right, this seems to me a rather odd question.
Asking how a block universe comes into existence presupposes that
this is a process that must happen within a time stream.
I can imagine a semi-block universe in which, as you've often
remarked, the past is a block and the universe keeps adding new
moments and growing. This would be like Barbour's time capsules,
except just sticking everything into one capsule, like a history
book that keeps adding pages. But yes it implies another exterior
"time" in which this "happens"; but then so does Bruno's UD.
I don't think Bruno would agree with that. I think the UD is
supposed to function simply by existing, and each state is defined
relative to another one....somehow. (But at this point my brain
melts...)
It is not so much that the UD exists, but that the whole UD* exists,
or better is emulated, in the "block-time" manner, in arithmetic.
I will say a little more on this in my reply to Kim.
Bruno
My point is that we needn't take these models seriously. We just
use them to try to picture things.
Right.... maybe.... not sure what you mean. That is, I'm not sure
where the line is between which models one should take seriously (if
any) and which ones are "just for picturing". Did Minkowski take
space-time seriously? Does it matter? I thought the important things
were prediction of (preferably unexpected) consequences, and being
open to refutation.
I assume as we get more into interpretation and general meta-ness,
refutation comes to rely more on logical inconsistency or similar
meta-refutations. But things can occasionally be "de-meta-ised" as
our knowledge improves. This happened for block universes with SR.
The experimental evidence for space-time being a 4D manifold is the
relativity of simultaneity. I assume that before this, the concept
was "just an interpretation" - it was the only picture that made
sense of Newtonian physics, but (apart from thought experiments like
"Laplace's godlike being") it was not considered experimentally
testable. You just had to accept it on logical grounds (or posit
extra time streams). Then along came Einstein, and showed that it
was experimentally testable after all.
I guess it's possible the MWI will undergo a similar "demetaisation"
at some point, perhaps if quantum computers factoring very large
numbers become commonplace...
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