Light travel distance is the distance light travels in free space in a given time, influenced by redshift, and is calculated as ‘light travel time’.
The proper distance refers to the distance between an observer and a source at a specific time t, which can change over time due to the expansion of the universe. It represents the distance between two galaxies at that time (t), which can also change due to the universe's expansion.
Comoving distance, a measure of the constant distance between the universe's expansion and its proper distance, remains constant despite changes in proper distance due to the expansion of space.
The Luminosity Distance depends on cosmology and it is defined as the distance at which the observed flux f is from an object. The Photon Energy gets red shifted. Where λ(obs), λ(emit) are observed and emitted wave lengths and a0,ae are corresponding scale factors.
