Distinction between special and general relativity

[martinbn]

Well, they are not there if they are not postulated.

But you said that your preference is that they are derived, so their are not postulated but derived, they are still their. Or are you saying that what you wrote above about Mercury is not GR.

I really don't know what we are discussing and where this is going! Anyway...

 

[atyy]

But you said that your preference is that they are derived, so their are not postulated but derived, they are still their. Or are you saying that what you wrote above about Mercury is not GR.

I really don't know what we are discussing and where this is going! Anyway...

Derived as an approximation, not exactly. In exact terms, the don't exist, because of the corrections. So conceptually we don't ignore the correction terms, it is just that the corrections are smaller than the experimental error.

Another way to say it is that if the test particles are postulated, then when experiment is fine enough to detect the deviations from geodesic motion, there is no theory that will systematically give you the corrections to match experiment.

However, if one uses the Einstein field equations without postulating test particles, then when experiment is fine enough to detect the deviations from geodesic motion, there is a theory that will systematically give you the corrections to match experiment.