Large-scale Structure of the Universe

By naked eye we can easily detect only three galaxies: the Andromeda galaxy in the northern sky, and the Large and Small Magellanic Clouds in the southern sky. Pictures taken via large telescopes contain millions of galaxies, and it is estimated that there are hundreds of billions of faint galaxies all over the sky. Also spectra of millions of galaxies have been obtained in recent years; hence, the distances to these galaxies are known with the help of the Hubble law (distance proportional to redshift). Thus it is possible to study how galaxies are distributed three dimensionally, indicating matter distribution in the universe. Previously, before the current “redshift industry,” astronomers could study only the two-dimensional distribution of galaxies on the celestial sphere.