- #36

PAllen

Science Advisor

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PAllen said:Not really. For radial free fall geodesic, both t coordinate and r coordinate change as a function of an affine parameter. For a radial spatial geodesic, the t coordinate does’t change at all. Thus, they are completely curves in spacetime.

But they are two different curves. The latter is not even well defined as such - you have to specify that you mean radial path in an SC coordinate constant time slice. Then, the spatial the spatial path is a geodesic of both the slice and the spacetime. For other coordinates, a radial spatial path need not be a geodesic of the spacetime, though it would normally be a geodesic of the slice.A.T. said:- The world-line of a radial free fall is a geodesic in space-time

- The spatial-path of a radial free fall is a geodesic in space

The claim under discussion was a specific path being a geodesic of the spacetime and the submanifold. Your example is simply not relevant in that you are talking about two different paths.