Changes

*The inference from the observations of spectra expressed in quantitative relationship (known as [[Hubble's law]]): the redshift of a [[galaxy]] thus its recessional velocity is:

*The inference from the observations of spectra expressed in quantitative relationship (known as [[Hubble's law]]): the redshift of a [[galaxy]] thus its recessional velocity is:

**proportional to its distance and

**proportional to its distance and

**inversely proportional to its apparent brightness or flux

**inversely proportional to its [[Star magnitude|apparent brightness]] or flux

This inference directly lead to theories on expanding universe, in the 1930s the front page of The [[New York Times]] declared: ''"We are living in an Expanding Universe"''.<ref name="BB never Happend">{{cite episode| title = Universe, the cosmology quest

This inference directly lead to theories on expanding universe, in the 1930s the front page of The [[New York Times]] declared: ''"We are living in an Expanding Universe"''.<ref name="BB never Happend">{{cite episode| title = Universe, the cosmology quest