A Map of Nothing by Scientific American

Cosmic voids are vast spaces that contain few or no galaxies—less than one-tenth of the average matter density found in the Universe. They may have been formed by oscillations of matter during the Big Bang—collapses of mass followed by implosions—that gave rise to small differences in the distribution of mass in the early Universe that grew over time. Dense areas collapsed more rapidly under gravity and created the foam-like structure of galaxy filaments and voids we observe today.
 
Some voids are “small” (30 million light-years) and some are not. The so-called Supervoids are the largest—such as the Eridanus Supervoid, which might be up to 1 billion light-years across. This void is hypothesized as an explanation for the “cold spot” in the cosmic microwave background radiation—the relic radiation reaching us from the Big Bang.

For a kind of nothing, voids have taught us a great deal about neutrinos, dark energy and cosmic evolution, to name a few. The graphic presents about 6,500 voids mapped by the Sloan Digital Sky Survey, drawn within the sphere of the Universe—some 13.8 billion light-years travel distance across.