When Wayne Gretzky retired from playing professional hockey, National Hockey League fans referred to his departure as the end of greatness. Nicknamed “The Great One,” he was so great that no hockey fan then or now can imagine that any hockey player coming close to matching Gretzky’s talent.
In an even more dramatic manner the universe displays an end of greatness. However, the end of this greatness—a feature of the early universe’s history—signals the beginning of purpose.
The universe on its largest size-scales (13.5 billion light-years across) appears to be a homogeneous distribution of randomly located superclusters of galaxies (see figure 1). This appearance of homogeneity and uniformity suddenly disappears, however, when one examines the structure of the universe on a somewhat smaller size-scale.
Astronomers refer to the sudden appearance of cosmic homogeneity and uniformity (as one observes cosmic structure at greater and greater volumes) as the “End of Greatness.”1 Cosmic volumes defined by spheres with diameters smaller than 840 million light-years depart from homogeneity and uniformity, manifesting magnificent interior designs (“greatness”).2
Elegant Cosmic Webs
On size-scale diameters of less than 840 million light-years the random, homogeneous, and uniform jumble of superclusters of galaxies gives way to ordered structures of galaxies, galaxy clusters, and gas. These ordered structures are cosmic webs. They look like soap foam bubbles with filaments and sheets of galaxy clusters and gases on the surfaces of the bubbles separated by giant interior voids (see figure 2). You can experience animated fly throughs of different cosmic webs in the following short YouTube videos:
The cosmic webs truly resemble soap foam bubbles. They form when spherical voids where very little matter exists are encapsulated by membranes that contain nearly all the ordinary matter (galaxy clusters, galaxies, dust, and gas) and nearly all the dark matter. Astronomers now understand why, on size-scales of less than 840 million light-years, cosmic structure is manifested as cosmic webs.
Cosmic Structure Formation
The voids formed as a result of baryon acoustic oscillations arising from the big bang creation event. (Baryons refer to the particles that comprise ordinary matter. Protons and neutrons comprise more than 99.9 percent of ordinary matter.) Baryon acoustic oscillations are fluctuations in the density of baryonic matter caused by acoustic density waves in the plasma (ionized matter) of the very early universe.
Tiny anisotropies in the quantum fluctuations of the universe when it was very much less than a trillionth of a second old grew larger as the universe expanded. High-mass density regions collapsed under the influence of gravity much more rapidly than low-mass density regions.
As this ordinary matter clumped together, it created pressure. This pressure was generated from the photons with which ordinary matter strongly interacts. The pressure counteracted gravity, creating ripples that radiated throughout the universe’s spacetime surface. These ripples are the baryon acoustic oscillations.
Dark matter, or exotic matter, interacts very weakly or not at all with photons. Hence, the pressure that causes the ripples (baryon acoustic oscillations) does not affect it. Thus, the dark matter remains at the centers of the ripples. The ordinary matter gets pushed out to form bubbles surrounding the centers of the ripples (see figure 3).
Some ordinary matter falls into the center of the bubble as a result of the gravitational attraction of the dark matter located there. The result is that most of the ordinary matter resides on the surface of the bubble and nearly all the remaining ordinary matter in the center of the bubble. The distribution of ordinary matter along the bubble surfaces takes the form of sheets of huge, closely packed aggregates of galaxy clusters and gas with filaments of galaxy clusters and gas emanating out from the sheets.
Web Design Leads to Life
The size of the bubbles that make up the cosmic webs are determined by the ratio of the quantity of dark matter to the quantity of ordinary matter, the quantity of each kind of matter, and the cosmic expansion rate. These three features of the universe explain the amazing interior designs of the cosmic webs that make possible the existence of physical life.
The bubble structures of the cosmic webs spread apart the galaxy clusters and the galaxies within the clusters by the just-right distances at the just-right times in the history of the universe to make possible the existence of advanced physical life. (Interested readers can learn much more about these just-right designs in two previous posts on supercluster design [part 1 and part 2]). In a historical context, the end of cosmic greatness is the beginning of greatness. Very early in the history of the universe, homogeneity and uniformity transitioned into magnificently great designs, great designs by the cosmic Creator that made it possible for us humans to exist, to thrive, and to fulfill our purpose and destiny.
Featured image: The Cosmic Web
Credit: Wikimedia Commons
- Harvard astronomer Robert Kirshner was the first to use “End of Greatness” to refer to the sudden appearance of cosmic homogeneity and uniformity as one observes at greater and greater cosmological distances. See, Robert P. Kirshner, The Extravagant Universe: Exploding Stars, Dark Energy and the Accelerating Cosmos (Princeton: Princeton University Press, 2002), 71.
- Susan Sarkar and Biswajit Pandley, “Unravelling the Cosmic Web: An Analysis of the Sloan Digital Sky Survey Data Release 14 with the Local Dimension,” Monthly Notices of the Royal Astronomical Society 485, no. 4 (June 2019): 4743–53, doi:10.1093/mnras/stz499; Morag I. Scrimgeour et al., “The WiggleZ Dark Energy Survey: The Transition to Large-Scale Cosmic Homogeneity,” Monthly Notices of the Royal Astronomical Society 425, no. 1 (September 2012): 116–34, doi:10.1111/j.1365-2966.2012.21302.x; Felipe Avila et al., “The Angular Scale of Homogeneity in the Local Universe with the SDSS Blue Galaxies,” Monthly Notices of the Royal Astronomical Society 488, no. 1 (September 2019): 1481–87, doi:10.1093/mnras/stz1765.