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A void is an empty space, and in astrophysics, the term is used for large empty spaces between large scale structures (such as galaxy sheets, galaxy walls, or galaxy filaments), the spaces with diameters on the order of 10 or 100 megaparsecs, with relatively little baryonic matter (i.e., very few stars, clouds, galaxies, etc.). They were first pointed out in 1978 by Stephen Gregory and Laird A. Thompson. Voids are of interest in cosmology, which aims to describe the distribution of matter in the universe. More voids than expected or larger voids than expected indicate some early influence that caused non-homogeneity in matter's distribution. Large voids (e.g., with diameters in the 100 megaparsec range) are called supervoids. Among the largest known supervoids is the Great Void or Eridanus Supervoid, which has a diameter on the order of a 150 megaparsecs.