# precession-of-Mercury vs 3-geometries: vocabulary for the difference?

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[If the answer to the question below is "no", then this post might be viewed as provocative. Sorry! But if the answer is "yes", then this post will have been a good thing. Only one way to find out.]

A member of the GR cognoscenti recently told me that, if f is a diffeomorphism, then f_* is routinely called the "push-forward" operation (on tensor fields). This bit of vocabulary has been a blessing. I'm now seeking a similar blessing. Here are two observables:

A. The precession of the orbit of Mercury is an observable that we compute with the help of classical GR. This observable is defined only in our particular state of reality.

B. If we (somehow) foliate spacetime into 3-geometries at differing times, then the (rather complicated) value of the 3-geometry at time t can be observed in any state.

It seems to me that A and B come from qualitatively different classes of observables. Are there routine names for these?

This post has been migrated from (A51.SE)
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