- #71
Hurkyl
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What do you mean by `the' Riemannian metric? There are lots of Riemann metrics, and if I recall the definition correctly, none of them are suitable for a space-time manifold.If, on the other hand, you apply (following Einstein) the Remannian metric, then ‘c’ is constant independent of the size of the region
And of course 'c' is a constant independent of the size of the region -- just like '2', 'e', and '-475 sq. in / Ampere-Coulomb' are all constants too.
So, I have no idea what you're trying to say here.
There's no imagination involved, nor any sort of transformation. There is an integral for computing the proper distance along a worldline: [itex]\int_\gamma \, ds[/itex]. If you plug the worldline of a photon into the integral, the answer is zero.From imagination, one could conclude that the path traveled by a photon is always zero if measured in its own proper frame. But to find this result formally, one has to transform the motion with use of the Lorentz transformation into the frame of the photon.
It sounds like you are confusing "coordinate displacement" with proper distance.the photon travels on a path with finite, non-zero length.
I don't remember anymore why I brought this up. (In fact, it really doesn't even make sense at all to ask the proper distance along the path something travels -- only what the proper time along its path was... which again is zero for a photon)
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