= Comoving and proper distances
{wiki=Comoving_and_proper_distances}
Comoving distance and proper distance are two important concepts in cosmology related to the measurement of distances in the expanding universe. Here's an overview of both terms: \#\#\# Proper Distance **Proper distance** is the distance between two points in space measured along a specific path at a given time. It is the actual physical distance that an observer would measure using a ruler at rest relative to the objects in question.
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