anyway, if the 3D VS 4D debate relates to spacetime theory as it seems, it looks like a matter of point of view, essentially if one takes a classical mechanics, or relativist/quantum mechanics stance
is that so?
No. First, forget quantum mechanics. Special relativity is usually phrased in terms of a space/time geometry, but it is one with a very peculiar "shape", which accounts for the unintuitive aspects of relativity. It is actually called Minkowskian space/time (after its inventor) as opposed to classical space/time, which is just ordinary space combined with ordinary time. The perdurant/endurant debate in ontology really hasnt got anything to do with mechanics at all, classical or otherwise. It is closer to the two ways of thinking about time, either time as a dimension ("calendar' or "clock" time) vs. thinking about the present (and only the present) as being 'real' and time being a kind of flow through reality which makes changes happen. One might call them respectively the physical idea of time vs. the perceptual or experienced view of time. THis is a much more philosophical kind of debate, nothing much to do with any kind of physics.
Pat
In physics, spacetime is any mathematical model that combines space and time into a single construct called the spacetime continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions. According to certain Euclidean space perceptions, the universe has three dimensions of space and one dimension of time. By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels. In classical mechanics, the use of Euclidean space instead of spacetime is appropriate, as time is treated as universal and constant, being independent of the state of motion of an observer. In relativistic contexts, however, time cannot be separated from the three dimensions of space, because the rate at which time passes depends on an object's velocity relative to the speed of light and also on the strength of intense gravitational
(WIKIPEDIA)
PDM
On Sat, Feb 21, 2009 at 2:52 PM, <paola.dimaio@xxxxxxxxx> wrote: Patrick
thanks for the detailed and pretty complex explanation
would it be wrong to simplify the assertion as
1. space and time are correlated, space does not exist without time, meaning that a 3d is a subset of a 4d
thanks P
On Sat, Feb 21, 2009 at 2:27 PM, Patrick Cassidy <pat@xxxxxxxxx> wrote: Ali, Rather than point to a long thread, I will summarize: The incompatibilities of 3D and 4D arise solely at the philosophical level. Perdurantists don't believe that 3D objects exist; endurantists don't believe that 4D objects exist. These are contradictory **belief systems**. But when one wants to make an assertion about an object's properties, it can be done equivalently in either form and translated accurately to the other form. Pat Hayes has one way of executing the translations, I have a different way. My own preferred way for the simple case of translating assertions about properties of an object is, to wit:
Assume {Obj123 isanInstanceOf Object3D} {Obj456 isanInstanceOf Object4D} {Obj456-200901-200902 isaTimeSliceOf Obj456} {Obj456-200901-200902 beginsOn Date20090101} {Obj456-200901-200902 endsOn Date20090201}
And also assume a bridging relation between the two views of that object: { Obj123 isThe3DcorrelateOf Obj456}
Now given the above, an assertion about that object in 4D "Time slice Obj456-200901-200902 of Obj456 is Red" {Obj456-200901-200902 hasAttributeValue Red} Is equivalent to an analogous assertion in 3D "Obj123 was Red from Date20090101 to Date20090201" {Obj123 hasAttributeValue Red from Date20090101 to Date20090201}
Or, in general, given the assumptions: (ó (?rel Obj456-200901-200902 @args) (?rel Obj123 @args from Date20090101 to Date20090201))
In summary, models that are incompatible on the philosophical level can be represented as different *theories*, but when practical assertions about real-world things are made in the *notation* adopted by either camp, those assertions can be translated accurately into equivalent assertions, having the same meaning, in the notation of the other camp. Having different philosophies about the fundamental nature of the universe doesn't mean that we can't *understand* each other when we talk about the universe. Whenever there are different preferred representations, the task of the FO will be to provide the translations that allow assertions from one viewpoint to the other.
Pat
Patrick Cassidy MICRA, Inc. 908-561-3416 cell: 908-565-4053 cassidy@xxxxxxxxx
Hello again, Can someone point me to discussion / papers which outline the irreconcilable(?) differences between these two paradigms. My (semi)naive impression is that each approach considers a set of information as a given, while another requires that it be explicated. It seems like a relatively straightforward affair to keep track of what is needed to facilitate adequate, two-way translation between each approach. Am i missing something? Why is this such a thorn? Where do the problems arise? Ali
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(•`'·.¸(`'·.¸(•)¸.·'´)¸.·'´•) .,.,
-- Paola Di Maio, **************************************** Forthcoming IEEE/DEST 09 Collective Intelligence Track (deadline extended) i-Semantics 2009, 2 - 4 September 2009, Graz, Austria. www.i-semantics.tugraz.at SEMAPRO 2009, Malta http://www.iaria.org/conferences2009/CfPSEMAPRO09.html************************************************** Mae Fah Luang Child Protection Project, Chiang Rai Thailand
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Paola Di Maio,
****************************************
Forthcoming
IEEE/DEST 09 Collective Intelligence Track (deadline extended)
i-Semantics 2009, 2 - 4 September 2009, Graz, Austria. www.i-semantics.tugraz.at
SEMAPRO 2009, Malta
http://www.iaria.org/conferences2009/CfPSEMAPRO09.html
**************************************************
Mae Fah Luang Child Protection Project, Chiang Rai Thailand
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