How to measure spatial distances?

TL;DR

This paper critiques the common practice of using space-like geodesics to measure spatial distances, arguing that time-like geodesics are more justified for temporal measurements and providing examples where space-like geodesics are inadequate.

Contribution

It challenges the conventional use of space-like geodesics for spatial distance measurement and offers examples illustrating their limitations.

Findings

Time-like geodesics are more justified for measuring temporal distances.

Examples show space-like geodesics can be inappropriate for spatial distances.

Abstract

The use of time--like geodesics to measure temporal distances is better justified than the use of space--like geodesics for a measurement of spatial distances. We give examples where a ''spatial distance'' cannot be appropriately determined by the length of a space--like geodesic.