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Topic: General relativity question
Replies: 4   Last Post: Nov 7, 2012 8:01 AM

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Posts: 409
Registered: 3/1/08
General relativity question
Posted: Nov 4, 2012 12:28 PM
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I can't say I fully understand general relativity, however, one
question keeps bothering me .
Consider a four dimensional pseudo-riemanian manifold .
It has a unique Einstein tensor ,that is divergenceless, therefore can
be equivalated to a stress-energy tensor .
All well and good .
However , I keep hearing about this "block universe" concept .
At least in Newtonian mechanics , one infinitesimal "slice" of space-
time is sufficient to determine both the future and past evolution of
the space time .
However , one three-dimensional (infinitesimally 'thick' in the fourth
dimension as to contain momentum information) slice of an arbitrary
four dimensional manifold is certainly not sufficient to determine the
whole manifold . And it is the whole manifold that determines the
matter-energy content .
It seems to me, the Einstein field equations leave way to many degrees
of freedom for a 'block universe' ) .
Is there something I'm missing? Some misinterpretation , or some extra
constrains on the "universe manifold" or the Stress-Energy tensor?

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