Large-scale structure surveys

Galaxies discovered by the Sloan Digital Sky Survey (SDSS). Red points are galaxies with more red star light, indicating older and often larger galaxies. The web-like distribution of galaxies on large scales can be seen by eye. A larger redshift corresponds to a larger distance from Earth, which is at center of the figure. The figure shows galaxies out to around 2 billion lightyears away. Figure Credit: M. Blanton and SDSS

simulation of gravity in an expanding Universe. As time goes on (left to right), gravity pulls together matter into large scale patterns. Notice that the pattern on the right (present day) has much more clustered structure than the left-most box (early in the Universe). Also, the Universe expands with time, so every ‘box’ in the Universe is also growing in size. Figure Credit: Andrey Kravtsov, Anatoly Klypin, National Center for Supercomputer Applications (NCSA).

The Large Scale Structure (LSS) of the universe refers to the patterns of galaxies and matter on scales much larger than individual galaxies or groupings of galaxies. These correlated structures can be seen up to billions of light years in length and are created and shaped by gravity. Just as gravity on smaller scales pulls together gas particles to make stars, and pulls together stars to make galaxies, it also pulls together galaxies and matter into patterns on larger scales. These patterns often contain large filaments of galaxies, and voids in between, somewhat resembling a spider web, which is why it is often referred to as ‘the cosmic web.’ (From https://www.darkenergysurvey.org)