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- Xref: sparky sci.math:13043 sci.physics:16345
- Newsgroups: sci.math,sci.physics
- Path: sparky!uunet!zaphod.mps.ohio-state.edu!darwin.sura.net!jvnc.net!nuscc!scip1061
- From: scip1061@nuscc.nus.sg (Marc Paul Jozef)
- Subject: Re: How do you draw a straight line?
- Message-ID: <1992Oct12.083128.29023@nuscc.nus.sg>
- Organization: National University of Singapore
- References: <1992Oct9.195430.22725@galois.mit.edu>
- Date: Mon, 12 Oct 1992 08:31:28 GMT
- Lines: 22
-
- jbaez@riesz.mit.edu (John C. Baez) writes:
- : In article <1992Oct8.115013.2533@nuscc.nus.sg> scip1061@nuscc.nus.sg (Marc Paul Jozef) writes:
- : >
- : > The spacetime metric of GR defines geodesics
- : >in spacetime. A string or a rod or whatever
- : >define world*sheets* in spacetime; `straightness'
- : >of a line has nothing to do with geodesics of GR.
- :
- : While it's true that over time a rod covers a 2-dimensional surface
- : in spacetime, the closest thing there is to a straight (spacelike) line
- : in GR is a spacelike geodesic.
- :
- :
-
- So what?
- The correspondence may be `close', but it can
- never be precise (except in static spacetimes
- which have a unique timelike Killing-field,
- so that there is a unique 3+1 splitting of
- spacetime).
-
-
-