Moving together or in a correlated way.
Fr.: coordonnées comobiles
A system of coordinates used in cosmology which is fixed with respect to the overall → Hubble flow of the universe. A given galaxy's location in comoving coordinates does not change as the Universe expands.
Fr.: distance comobile
1) A distance in → comoving coordinates
between two points in space at a given cosmological time. In other words,
the distance between two nearby objects in the Universe which
remains constant with epoch if the two objects are moving with the
→ Hubble flow.
More specifically, it is the → proper distance
divided by the ratio of the → scale factor
of the Universe between then, a(t)em,
and now, a(t)obs:
DC = Dproper .
In terms of → redshift (z),
it is the proper distance multiplied by (1 + z).
At the present epoch, i.e. a = a(tobs) = 1,
DC = Dproper.
If the objects have no peculiar velocity their comoving distance at
any time is the same as their distance today.
Fr.: rérérentiel comobile
A → reference frame that is attached to a moving object. The object in this frame is therefore at rest.
Fr.: volume comobile