Current cosmological models suggest that the observable universe is a spherical space-time with a radius of 46.5 billion light-years centered on Earth and containing at least 2 trillion galaxies.
The Milky Way is located in the Local Group and the Local Cluster, which is located in the Virgo Supercluster, and the Virgo Supernova Cluster, which is located in the larger Laniakea Supercluster, where the Milky Way is a mere grain of sand in a super system shaped like a feather.
But is Laniakea the largest cosmic structure?
The answer is no.
For the past 10 years, a team of astronomical researchers at the University of Hawaii has been mapping the distribution of galaxies around the Milky Way, and the Laniakea Supercluster has been uncovered in the process, but the biggest reward is not Laniakea, but another superstructure above it, the "South Pole Wall.
The superstructure is called the South Pole Wall because its projection in the Earth's sky is just above the South Pole, and computer simulations show that this supercluster of galaxies, shaped like an arm, is embracing the Laniakea Supercluster and also the entire Milky Way galaxy.
This superstructure, spanning 1.4 billion light-years, is projected over a length of 500 million light-years in the South Pole region, and extending along a 200-degree arc, it also folds inward to within 300 million light-years of the Milky Way, eventually merging with the Shapley Supercluster in the observable universe. The Laniakea Supercluster, which houses 100,000 galaxies in 500 million light-years in diameter, still looks a bit small in front of the South Pole wall.
However, the Antarctic Wall is not the largest cosmic structure discovered so far, the first one is a cosmic structure called the "Great Wall of Sloan".
But before introducing it, we must first understand what the "Great Wall of the Universe" is
It is well known that galaxies in the universe form galaxy clusters, galaxy clusters form galaxy clusters, and galaxy clusters form superclusters, which are generally hundreds of millions of light years in diameter.
Cosmologists have found that if the field of view is expanded from hundreds of millions of light-years to billions or tens of billions of light-years, superclusters of galaxies that appear to be independent of each other will appear as a network of fibers, and the fibers of galaxies are called the "Great Wall of the Universe", and the areas between these fibers filled with dark matter and dark energy are called "cosmic voids".
The longest and thickest fiber discovered so far is the superstructure known as "The Great Wall of Sloan", which is located 1 billion light-years away from the Earth and has a length of 1.37 billion light-years itself. For the observable universe with a radius of only 46.5 billion light-years, a giant fiber structure of 1.37 billion light-years long is already considered one of the important components of the observable universe.
If we take into account the tens of billions of light-years of space-time around which the Great Wall of Sloan affects with its own gravity, it actually controls a significant portion of the celestial systems in the observable universe, at least our Milky Way and the Laniakea Supercluster are under the influence of the Great Wall of Sloan, and the future evolution of the universe will also be affected by it.
So how will the universe evolve in the future?
If the current estimates of the percentage of dark matter and dark energy are correct, then our universe will actually die out in an eternity of accelerated expansion, because the ordinary matter that makes up galaxies and planets and humans themselves only accounts for 4.9% of the total mass and energy of the universe, leaving 26.5% of dark matter and 68.3% of dark energy as the mainstream of the universe.
While dark matter keeps galaxies from falling apart, dark energy keeps the universe expanding at an accelerated rate, so with a dark energy ratio of nearly 70%, the expansion of the universe's space-time will only get faster, and the range of expansion forces will gradually decrease from the current million light-year level, that is, from tearing superclusters to tearing galaxy clusters, then galaxy groups, and then individual galaxies.
In the most extreme case, when the rate of expansion of the universe reaches a critical point, all the atoms in the entire universe will be pulled by this force and be torn apart, that is, including humans, all the objects in the universe made of ordinary matter, will cease to exist in the great tear.
As for the above-mentioned Antarctic Wall and the Sloan Wall and the Laniakea Supercluster, they will be the first celestial structures to be torn apart by the forces of cosmic expansion, because their own mass and volume are too large, the forces of cosmic expansion will be the first to act on them, but the Milky Way and the Solar System, such small players live longer.