First, Humankind became aware that the visible stars tended to move across the sky more or less in unison, and thus formed some sort of group. In time, this came to be called the Milky Way Galaxy, and was thought to comprise the entire Universe. Other objects that, through a telescope, appeared to have a structure were considered as nebulosity within the Milky Way. Indeed, the Andromeda Galaxy, our closest large neighbor, was originally called the Great Andromeda Nebula.
Once it was confirmed that the Milky Way galaxy was but one of billions of galaxies in the Universe, patterns started to become apparent in the distribution of the galaxies. These became known as Groups, for the smaller agglomerations, or Clusters. Then these clusters appeared to group themselves across the cosmos, so we had Superclusters. Finally, with improved techniques in telescopes, and using different wavelengths, the entire cosmos was seen to have a filamentary structure with Superclusters strung together across the Universe. Astronomers looking at this structure identified a number of huge areas in which galaxies were absent. These have become known as Voids and, surprise surprise, Supervoids for the REALLY large ones!
Then we take a brief look at some of the projects that have contributed recently to extending our knowledge of the structure of the Universe on these immense scales. In particular, the various analyses of the Cosmic Microwave Background. Finally, we look at the incredibly surprising observations that the rate of expansion of the Universe is accelerating rather than slowing down.
Astronomy & Cosmology
Large Scale Structure of the Universe
This diagram shows some of the major Superclusters, Walls and Voids out to a radius of about 500 million light-years from the Earth.