On Wed, Dec 19, 2018 at 6:00 AM Bruce Kellett <[email protected]> wrote:
> On Wed, Dec 19, 2018 at 10:40 PM Jason Resch <[email protected]> wrote: > >> On Tue, Dec 18, 2018 at 11:14 PM Bruce Kellett <[email protected]> >> wrote: >> >>> From: Jason Resch <[email protected]> >>> >>> On Tue, Dec 18, 2018 at 7:27 PM Bruce Kellett <[email protected]> >>> wrote: >>> >>>> On Wed, Dec 19, 2018 at 12:19 PM Jason Resch <[email protected]> >>>> wrote: >>>> >>>>> On Tue, Dec 18, 2018 at 6:45 PM Bruce Kellett <[email protected]> >>>>> wrote: >>>>> >>>>>> On Wed, Dec 19, 2018 at 11:27 AM Jason Resch <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> On Tue, Dec 18, 2018 at 6:05 PM Bruce Kellett <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> On Wed, Dec 19, 2018 at 11:02 AM Jason Resch <[email protected]> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> On Tue, Dec 18, 2018 at 3:23 PM John Clark <[email protected]> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> >>>>>>>>>> Arithmetical computations don't change so there can't be a >>>>>>>>>> correspondence between them and the evolution of spacetime or >>>>>>>>>> with anything else that can change. >>>>>>>>>> >>>>>>>>> >>>>>>>>> "y = 2x+1" defines the arithmetical relation of "oddness". >>>>>>>>> >>>>>>>>> Solutions to this equation yield (compute) for *y* all possible >>>>>>>>> odd numbers. *y* changes with respect to increasing values of *x*, >>>>>>>>> just as John Clark's brain changes with respect to increasing values >>>>>>>>> of >>>>>>>>> *t*. >>>>>>>>> >>>>>>>> >>>>>>>> How does 'x' change? >>>>>>>> >>>>>>> >>>>>>> With respect to y, and vice versa (like your brain state and your >>>>>>> location in spacetime). >>>>>>> >>>>>> >>>>>> Poor analogy. Change in the physical world is governed by dynamics, >>>>>> described by equations with a veritable 't', called time. Time is >>>>>> probably >>>>>> only a local phenomenon, but I do not see any 'time' variable in >>>>>> arithmetic. >>>>>> >>>>> >>>>> It depends on the equation. >>>>> >>>> >>>> What equation? There are no dynamics in arithmetic. >>>> >>> >>> There are computations. >>> >>> But no dynamics. >>> >> >> I'm not sure what this means. Not dynamic in what sense? >> > > Dynamics is the study of matter in motion. There are no clocks in > arithmetic. > Matter only moves with respect to different times, likewise the state of a computer's registers and memory only change between steps of a CPU. You could study the dynamics of state changes in a computer. > > >> The analogy with the block universe idea is useless, because the block >>>>>> universe idea is only a picture, not a reality. Special relativity merely >>>>>> abolishes any notion of Newtonian absolute time, it does not prove that >>>>>> all >>>>>> instants of time are equally and simultaneously existent. The whole >>>>>> notion >>>>>> of simultaneity is abolished in relativity. Minkowski's block universe >>>>>> was >>>>>> a response to this, but not a very good picture in the final analysis, >>>>>> because it completely fails to capture the local dynamical aspect of the >>>>>> time variable. >>>>>> >>>>> >>>>> Did you read https://core.ac.uk/download/pdf/11921131.pdf ? >>>>> >>>> >>>> No. Why should I? >>>> >>> >>> Because you believe relativity cannot be used to justify the block >>> universe concept. >>> >>> >>> I do not have the time or inclination to rebut every argument that is >>> presented in arbitrary papers. But if you abandon the idea of >>> 'simultaneity' as used in this paper, the objections to the idea of "the >>> present" as a ourely local concept collapse. >>> >>> >> Then you have already abandoned the idea of a 3-dimensional space >> evolving in time. How does this not leave "block time" as the only view >> that preserves an objective global spacetime? Why give up an objective >> realist view that captures all of spacetime when you do't have to? >> > > In what sense has this given up an objective global spacetime? All that > has been abandoned is the concept of a universal time parameter which could > give unique sense to global time slices. One can imagine such a foliation > of space like hyper surfaces if one wants to, but it is not imposed by > relativity. > But relativity does rules out "naive presentism" -- the idea that there are is an objective spacelike hypersurfaces that we can call a present. You seem to agree with me on this. What I am struggling with is the interpretation of time, or of the present, when you reduce present moments to single points in space time. What does this buy you? It seems to make it much harder to talk about the relationship between remote points in space time. For example, how do they effect one another? How can one talk about machines (such as our own brains) which are extended in space time, when we can only talk about individual atoms, or neurons existing in their own present, when they must interact with other neurons whose signal remains but that neuron now no longer exists (being in its own present time different from the perspective of the neuron which received its signal). It just seems so much more complicated to add the notion of popping into and out of existence, when it is wholly unnecessary and adds nothing to the theory. > The problem with the "objective realist view" to which you seem to wish to > cling is that not only is it not required by SR, it is positively ruled > against by quantum mechanics, particularly non-local EPR-type correlations. > I don't agree EPR has any bearing on this topic, but also don't want to re-open that can of worms here. > > This reminds me quite a bit of the break down of the naive conception of >> personal identity. The normal view is each person's experiences are >> bounded by either psychological or biological continuity. Thought >> experiments such as duplicating or permuting minds show neither of these >> can work. The only consistent choices that remain are: >> 1. "universalism" -- all experiences belong to one universal experiencer >> 2. "no-self" -- there are only single individual thought moments >> > > Your person-duplicating thought experiments have no such drastic > consequences -- there are other possibilities. > > I would like to hear what they are, as I am not aware of them. > The thought experiments of relativity, such as the Rietdijk-Putnam >> experiment, lead to a similar break down. You either reduce what exists >> "presently" to a collection of independent events (points) in space time, >> or you expand it to include all of space time. But in both cases, you are >> saying what exists in the present is the same (all points in space time vs. >> all of space time). I'm not sure you there is really a conceptual >> difference. >> > > There are many presents. Each present is purely local. > So ontologically speaking, all that exists right now is what? The single currently firing neuron in your brain that was the last neuron firing necessary for you to realize your conscious experience of reading this e-mail? No other neurons, and no other human beings, nor any other planets exist right now, because all that exists is the event that immediately surrounds you? > > >> What is your interpretation of the >>>>> https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument ? >>>>> >>>> >>>> The "present" is a local concept which cannot be extended to global >>>> hyperplanes. >>>> >>> >>> Which would means there is no such thing as a present point in time. >>> >>> > Of course not. There is no "present" for the whole of spacetime. I thought > that was the point I was trying to make.The "present" is a local > phenomenon. > What is the extent of the local present?, 1 lightyear, 1kilometer, 1 meter, 1 mm, 1 angstrom, 1 Plank length? > > No, the idea has no such implication. >>> >> >>> >>> Remember, the only sensible definition of "time" is an operational >>>> definition -- "time is what is measured on a clock". This is a purely local >>>> concept. >>>> >>> >>> So then you have reduced the present to a point in spacetime, a single >>> event. >>> >>> >>> Strictly speaking, yes. But for practical purposes, the spatial extent >>> of the "present" can be defined as that region over which the travel time >>> of a light signal is negligible compared to the characteristic time scale >>> of the processes of interest. >>> >> >> So strictly speaking, every event in spacetime exists in its own present. >> > > Yes. > > Isn't this the same as saying everything exists in the present? >> > > No, because there is no such thing as a universal "present". > I agree there is no universal present. But you say each event has its own present. So each event exists in its own present. If there is no single present but one for each local event, then you might as well say ell presents exist, no? > > >> i.e. everything in space-time exists? >> If not, then what experiment could be done to determine between the >> block-time view of space time and this theory of every event in space-time >> existing in its own present? >> > > Why should there be an experiment that could distinguish these ideas? The > point is that the block universe view is not a necessary consequence of SR. > And it becomes even clearer that it is not a viable view when you take GR > into account. > > This would make "dynamics", an artifact of personal experience, not of the objective reality. If you agree with me that block time is a possibility, not ruled out by our experience, then our experience of a dynamically evolving universe is compatible with a static block time universe too. This was the only point I was trying to get to. Platonic computations exist timelessly, and change is only a subjective phenomenon of conscious minds present within the structure that evolves over some dimension (be it some *t* or a CPU's clock or counter) > It isn't clear to me how those concepts even differ philosophically >> speaking. >> > > Of course they differ: in one case you have a purely local concept of the > present; in the other case you require some global notion of a "present", > which cannot even be uniquely defined. > > What exists? A: *naive presentism*: only a 3-dimensional space evolving in time (some particular "slice" of spacetime exists, which constantly changes) B: *local-presents*: Events, each in their position in space time, each in their own present time C: *block-time*: Events, each in their position in space time We both agree relativity rules out A. But I struggle to see the difference between B and C (ontologically speaking), unless you are proposing the view that the only thing that exists is a single event (I don't think you are though). Jason -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
