The Architecture of Everything
On the largest scales, the universe resembles a three-dimensional sponge. This structure, known as the cosmic web, is made of filaments, clusters, and enormous, nearly empty voids. The filaments are immense, thread-like formations of galaxies, gas, and dark matter that can stretch for 50 to 80 megaparsecs (160 to 260 million light-years). Some, like the Sloan Great Wall, are even larger, measuring nearly 1.5 billion light-years in length. Where these filaments intersect, they form dense nodes known as superclusters, which can contain thousands of galaxies. Our own Milky Way galaxy resides within the Laniakea Supercluster, a structure spanning 520 million light-years and containing the mass of 100,000 galaxies like our own.
The dominant component of this web is invisible. Dark matter, which makes up about 27% of the universe's content, is the underlying structure. baryonic matter—the stuff of stars and planets—accounts for only about 5% and is drawn by gravity into this dark matter framework. The vast regions between the filaments are cosmic voids, which make up about 80% of the universe's volume. The largest confirmed void, the Boötes Void, is a roughly spherical region about 330 million light-years in diameter that contains only about 60 known galaxies, whereas a typical volume of its size would be expected to contain thousands.