**Stephen Paul King** (*stephenk1@home.com*)

*Wed, 29 Sep 1999 02:27:44 GMT*

**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Next message:**Matti Pitkanen: "[time 831] Re: [time 830] Re: Does a fundamental time exist in GR and QM? The thinking of others..."**Previous message:**Stephen P. King: "[time 829] Re: [time 827] Re: [time 825] Chu spaces, causality, local systems... quantum laws of form? ..."**In reply to:**Ben Goertzel: "[time 825] Chu spaces, causality, local systems... quantum laws of form? ..."**Next in thread:**Matti Pitkanen: "[time 831] Re: [time 830] Re: Does a fundamental time exist in GR and QM? The thinking of others..."

On 12 Aug 1999 04:24:22 -0700, baez@charity.ucr.edu (john baez) wrote:

*>In article <37B08A95.4B9D9053@dcwi.com>, Ralph Frost <refrost@dcwi.com> wrote:
*

*>
*

*>>If you would be so kind as to expand a bit on the things you are saying
*

*>>here, I think you might avert some people from going astray.
*

*>
*

*>While causing others to go still further astray... okay, I'll risk
*

*>it.
*

*>
*

*>>I certainly might be one of those people who would be tempted to read in
*

*>>that what Rovelli seems to be saying agrees with the simplified notion
*

*>>that "experience exists, but time does not".
*

*>
*

*>I wouldn't want to say whether Rovelli's remarks do, or don't, agree
*

*>with this. The main reason is that physics rigorously shies away from
*

*>talking about "experience", preferring to leave that can of worms to
*

*>psychologists, philosophers, and other brave souls. Physics confines
*

*>itself to the thin sliver of reality that can be accurately quantified.
*

*>The concept of "experience" is not presently part of this thin sliver.
*

*>
*

*>>_I_ see this as
*

*>>fundamental but I expect you are, however, making reference to much more
*

*>>complicated mathematical expressions, correct?
*

*>
*

*>In fact it's the notion of "experience" which is the really complicated
*

*>thing, not the mathematical expressions that Rovelli is referring to.
*

*>Mathematics deals only with things that are so simple that they can
*

*>be described with utter precision - so precisely that even a computer
*

*>can deal with them. Most things - like "experience" - are too complicated
*

*>to be described in this way (at least for now). These things may seem
*

*>simple, because we are familiar with them, but as soon as you try to
*

*>describe them in a completely precise way - e.g., to write a computer
*

*>program that can "experience" - the crushing weight of their complexity
*

*>is made apparent. What many people take to be the complexity of
*

*>mathematics is really just the difficulty of learning unfamiliar
*

*>concepts at a high level of precision, no matter how simple they are.
*

*>
*

*>>At the simple level, heck, maybe mine is just a private notion, I see
*

*>>this "problem with time" as intimately wound into the limited scope of
*

*>>contemporary physics. By NOT accomodating ~consciousness~ [or whatever
*

*>>you want to call it], all the various descriptions and theories in
*

*>>physics make _perfect sense_ for as far as they can go. Yet, when that
*

*>>boundary is breached and one notes that the entire system present us
*

*>>with experience, not time, imo some of the temporal equations and
*

*>>relationships take on a much more "grossly approximate" hue.
*

*>
*

*>Hmm. I'll just say this: there are lots of mysterious things
*

*>about time, but in quantum gravity, the "problem of time"
*

*>is a very specific technical problem, namely: how to recover a
*

*>theory in which time evolution is described by a 1-parameter
*

*>unitary group as a limiting case of a theory without a Hamiltonian,
*

*>but merely a Hamiltonian constraint. You'll notice that I'm
*

*>throwing around a lot of technical jargon here! I'll give a
*

*>somewhat more simplified description below, but right now I'm
*

*>trying to make a particular unhappy point: I want to make it
*

*>clear that the "problem of time" in quantum gravity can only be
*

*>understood after one has spent a while seriously studying physics.
*

*>It is not the sort of problem that can be translated into everyday
*

*>terms without mangling it almost beyond recognition. It *does*
*

*>have a philosophical aspect to it that can be explained without
*

*>any physics jargon, and it's very important to understand this
*

*>aspect - to "see through all the clutter of technicalities" - but
*

*>unless one *also* understands the technical aspects, one can't
*

*>see that it is a very precise problem, possibly with a very
*

*>precise solution - one is at best dealing with a caricature of
*

*>the problem. In particular, one may be misled into thinking
*

*>that "consciousness" or "experience" play an important role
*

*>in this problem. I'm pretty sure they don't!
*

*>
*

*>>But the yellow caution flag you throw out is aimed at pointing out that
*

*>>ALL the quantitative relationships do indeed only exist in the temporal
*

*>>models. Is that close to what you are trying to express?
*

*>
*

*>Not really - I'm not sure I even understand what you mean!
*

*>
*

*>>If not, can you expand
*

*>>a bit on what you are afraid some people might do, please?
*

*>
*

*>Listing all the things I am afraid some people might do would make
*

*>this a very long post. However, I suppose the thing I am most
*

*>afraid *you* are doing is thinking that "experience" has much to do
*

*>with the problem of time.
*

*>
*

*>>> Yes - as long as you keep in mind that "derived versus fundamental"
*

*>>> is not a fundamental distinction.
*

*>>
*

*>>Can you clarify what you mean, here? I keep thinking that folks did
*

*>>their level best to evolve a very good fundamental theory.
*

*>
*

*>In a theory of physics we typically start with some assumptions and
*

*>derive some conclusions from these. We call the assumptions
*

*>"fundamental" - especially if they are simple and we keep using
*

*>them over and over again in different contexts - and we call the
*

*>conclusions "derived". But as theories change, what was once
*

*>"fundamental" may become "derived", and what was "derived" may
*

*>become "fundamental". This is what I meant by the wisecrack above.
*

*>
*

*>In particular, the idea that time is represented by a real number
*

*>t is considered fundamental in much of quantum mechanics, but
*

*>will certainly be derived in any good theory of quantum gravity.
*

*>We don't know exactly how this will work yet - and that's the problem
*

*>of time in a nutshell.
*

*>
*

*>I'll add, though, that there has been a huge amount of progress
*

*>on the problem of time over the last couple of decades, so it's
*

*>not as if we are *completely* floundering around in the darkness.
*

*>In fact, right now I think there are other more pressing problems
*

*>in quantum gravity.
*

*>
*

*>
*

*>
*

*>
*

*>
*

*>
*

**Next message:**Matti Pitkanen: "[time 831] Re: [time 830] Re: Does a fundamental time exist in GR and QM? The thinking of others..."**Previous message:**Stephen P. King: "[time 829] Re: [time 827] Re: [time 825] Chu spaces, causality, local systems... quantum laws of form? ..."**In reply to:**Ben Goertzel: "[time 825] Chu spaces, causality, local systems... quantum laws of form? ..."**Next in thread:**Matti Pitkanen: "[time 831] Re: [time 830] Re: Does a fundamental time exist in GR and QM? The thinking of others..."

*
This archive was generated by hypermail 2.0b3
on Sat Oct 16 1999 - 00:36:42 JST
*