ontolog-forum
[Top] [All Lists]

## Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah)

 To: ontolog-forum@xxxxxxxxxxxxxxxx "John F. Sowa" Thu, 27 Jan 2011 12:04:52 -0500 <4D41A5B4.1020601@xxxxxxxxxxx>
 ```On 1/27/2011 11:17 AM, Ian Bailey wrote: > I get 4D, finally, after years of hanging on Chris and > Matthew's coattails, but the 3D+1 thing is a mystery.    (01) The basic issue is the definition of a physical object and its relationship to a privileged time called 'now':    (02) 1. In 3+1 D, which is the implicit assumption in ordinary language, an object (human, animal, plant, or artifact) comes into existence at some time t1 (e.g., birth), ceases to exist at some time t2 (e.g., death), and for each now between t1 and t2, all parts of it exist together now.    (03) 2. In 4D, a physical object extends over a 4D volume, whose lower and upper time coordinates are t1 and t2 and whose spatial coordinates trace out a volume that spans the object's travels.    (04) 3, In 3+1 D, the object undergoes various changes, which cause some properties to become true or false at different times called now.    (05) 4. In 4D, the object doesn't change, but it has time-dependent parts (slices or stages) at which various properties may be true or false.    (06) The analogy I prefer (since I studied fluid mechanics at one time in my life) is between Lagrangian and Eulerian coordinate systems for representing and computing fluid flow:    (07) 1. Lagrangian coordinates are like a 3+1 D system: the observer follows a particular parcel of fluid as it moves.    (08) 2. Eulerian coordinates are like a 4D system: the observer sits on the side and watches the flow of all the fluid as a whole.    (09) In our ordinary language, we talk about our bodies in Lagrangian terms. We observe our own motion through space and time, and relate everything else to where we are *now*.    (010) An Eulerian system is like a God's eye view of the universe. God sees everything spread out in all dimensions of space and time. There is no privileged point of time or space.    (011) John    (012) _________________________________________________________________ Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/ Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/ Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx Shared Files: http://ontolog.cim3.net/file/ Community Wiki: http://ontolog.cim3.net/wiki/ To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (013) ```
 Current Thread Re: [ontolog-forum] Categorical Views of a Universe, (continued) Re: [ontolog-forum] Categorical Views of a Universe, Patrick Cassidy Re: [ontolog-forum] Categorical Views of a Universe, Rich Cooper Re: [ontolog-forum] Categorical Views of a Universe, Ron Wheeler Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Chris Partridge Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Matthew West Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), John F. Sowa Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Matthew West Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), John F. Sowa [ontolog-forum] 3D+1 (was presentism...was blah blah blah), Ian Bailey Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah), Dave McComb Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah), John F. Sowa <= Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah), Ian Bailey Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah), Chris Partridge Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah), Matthew West Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Ronald Stamper Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Rich Cooper Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Ronald Stamper Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Christopher Menzel Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Chris Partridge Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Christopher Menzel Re: [ontolog-forum] Presentism (was Re: Ontology of Rough Sets), Chris Partridge