Do you think the universe has boundaries? This question has been debated for years, and in 2018, it seemed that there was a definite answer.
At that time, there was a widely circulated news: a "high wall" was found in the depths of the distant universe, which stretched for 3.5 billion light years, and it was out of the universe when it crossed the high wall.
(Clusters of super-galaxies in the universe)
In fact, this news is just a misreading of scientific research by the general public. The so-called wall is not the boundary between the inside and outside of the universe, but the larger celestial structure within the universe.
Yes, you read that right, the length of the structure is large enough in light years, and it is also "billion". More crucially, it's not the biggest one ever discovered.
The largest celestial body described by a parsec instead of a light-year
Generally speaking, the light-year is the largest unit of length in the field of astronomy, but if it rises to a larger scale, that is, when a set of numbers is followed by a few more zeros, there is a parsec above the light-year.
The parsecs describe a farther distance than a light-year, but in general, this unit is only used by astronomers in their daily work – to keep the values as low as possible and to facilitate calculations and presentations.
After 2013, the role of the parsec became more practical, and larger celestial structures were discovered in the depths of the universe.
In November of that year, astronomers used satellites and radio telescopes to search for and observe multiple gamma-ray bursts in the depths of the universe. With the depiction of the location of the eruption, a startling discovery was made.
It turns out that in the area of gamma-ray bursts, there is an unimaginable giant structure, a huge celestial body composed of countless galaxies, which together build this giant structure.
How big is it? The longest distance at the observable end is more than 10 billion light-years. Even when converted into parsecs, it's a staggering 3 billion parsecs. The other end is relatively short, but it can also reach 7.2 billion light-years, or 2.2 billion parsecs.
Later, this super-large structure was named the Great Wall of Wuxian-Beimian Seat. The name means that the constellations Hercules and the Northern Corona are due to the fact that the projection position of the celestial body is exactly in the region of both.
As for the Great Wall, it not only literally means "city wall", but also refers to the celestial structure in the universe that resembles a long city wall. In the description of cosmic objects, the "Great Wall" represents a larger structure than the structure of "supercluster", "galaxy cluster", and "galaxy group" that the public has often heard of.
Large-scale structure
In astronomy, the concept of the Great Wall was first proposed in the 80s by John Thutzlau and Margaret Geller. This is often referred to as a large-scale structure, or a large-scale structure.
This large-scale celestial body is made up of galaxies like the Milky Way. For example, imagine the universe as a loofah, and the loofah inside is reticulated, and the large-scale structures in the universe are these reticulated structures.
Moreover, the network structure is three-dimensional, not flat, and the structure is irregular, at least in the current range of human observation. Therefore, the large-scale structure is also called the large-scale fibrous structure.
In their early studies, astronomers believed that all matter in the universe was evenly distributed. It was not until the 80s of the last century that it was gradually discovered that the distribution of galaxies in the universe was not uniform, and some areas appeared dense and some were very sparse.
What does that mean? That is to say, under the action of gravity, where the material polymerizes high, the gravitational force is strong, and it will continue to absorb other substances around it, and the density of the polymerization will become higher and higher.
On the other hand, there are areas where the original gravitational attraction is small, and no effective aggregation of matter is formed, and then a void without matter will be formed in the universe.
Just like the loofah, the aggregated matter forms a network structure, and those empty areas are equivalent to no substance.
From our field of vision, the earth seems to be very empty, but in fact, the solar system, which includes the earth, and the Milky Way, which includes the solar system at a higher level, are in the network structure of the universe. It's just that we humans are in it, and we can't see where we are.
Some people may be puzzled, isn't it said that it is a network structure, then it should be connected into a "line", but between planets, between star systems and even larger galaxies, the distance between each other is very far and empty.
The emptiness we perceive is due to the fact that from our own microscopic point of view, we feel that these stars are far away from each other. But if you look at it from a macroscopic point of view, from the perspective of the entire scale of the universe, where there are galaxies and where there are none, it looks obvious.
The most intuitive example, when we look at the Milky Way in the clear night sky, is a long straight line. But the actual lines are galaxies, and they are very far away from each other.
Therefore, from a macro perspective, the size of the scope of perception constitutes the whole picture in the field of vision. For example, if you are looking at the front of you from the top of a tall building, or you are sitting on an airplane looking down, the field of view is different.
If you are in outer space, you can see the whole picture of the earth, if you have the same view as the Milky Way, you will be able to see the whole picture of the stars in the solar system, and if you have a view of the size of the universe, you can see the network of superclusters and clusters of galaxies.
Obviously, human beings do not have such a large field of vision, and therefore can only see a part of the universe instead of the whole picture. However, if we abandon the macroscopic perspective and look at the microcosm, we will find that the structure of matter seems to be similar to the structure of the universe.
For example, if you look at a leaf with the naked eye, you can see the veins and veins of the leaf and the leaf itself. At this time, if you look at it with a magnifying device, you will find that the linear and lamellar structures under the naked eye are also composed of tiny cells. The point is that the cells are not densely distributed between each other, and there are also areas of holes.
Therefore, through the similarity, it can be understood that the large-scale structure is the larger shape of the universe under the human vision.
The galaxies and planets that make up the Great Wall
Essentially, the use of the Great Wall to describe large-scale structures is an analogy and a joking term for astronomers. The giant structure discovered by astronomers in 1989, although not as large as the Great Wall of Wuxian-Northern Corona discovered in 2013, is also a staggering 760 million light-years long and more than 200 million light-years wide.
The thickness of the "wall" alone has reached a staggering 15 million light years. What is this concept? It is said that it has been calculated that the accumulation of the Great Wall will be only 1 light-year long if 1.3 billion Great Walls are connected together.
So from a longer distance, it does look like a long wall. At the time of discovery, astronomers thought that such a massive structure would not be able to withstand the effects of gravity. However, after simulation calculations, it was found that it was still in the theoretical value range.
Astronomers at the time did not realize that with the discovery of the Great Wall, a larger vision of the universe opened up to mankind. By 1991, astronomers had discovered an even larger Great Wall, which was a staggering 580 million parsecs long.
Then, in 2003, another giant structure named the Sloan Great Wall appeared. It is 1.37 billion light-years long, another 600 million light-years longer than previously discovered megastructures.
In 2011, the astronomical community discovered U1.11, which is 780 million parsecs long, nearly double the previously discovered Sloan Wall. Then the Great Wall of Martial Immortals-Northern Crowns appeared, and its length exceeded 10 billion light years.
In the future, there may be even larger structures that break human cognition. But no matter how big these megastructures are, they are essentially made up of galaxies and even stars.
Giant structures like the Great Wall are made up of huge superclusters of galaxies. Astronomers have discovered more than 10 million superclusters in the observable universe.
The superclusters are composed of galaxy clusters, and the number of galaxy clusters under each supercluster can range from dozens to thousands.
The next level of galaxy clusters is made up of galaxies like the Milky Way. In a galaxy cluster, there are more than a few thousand galaxies.
If the number of galaxies is small, only a few dozen, it is called a galaxy group. The Milky Way galaxy we are in is located in the local galaxy group, which has about 50 galaxies.
In contrast, the largest cluster of galaxies in the local group is the Virgo Cluster, which consists of more than 2,500 galaxies.
At the level of the Milky Way, it is almost the smallest structure close to the universe. Further down, there are individual star systems. In our galaxy, there are at least 200 billion to 300 billion stars.
On the whole, the planets revolve around the stars, the star combination forms a galaxy, the galaxy combination forms a galaxy group or cluster, the galaxy cluster then combines to form a supercluster, and the supercluster combination forms the Great Wall.
Each set is staggeringly large, and each set expands infinitely when it is included in a larger set. Therefore, we can understand that stars are the basic units of galaxies, and galaxies such as the Milky Way are the basic units of the Great Wall.
In this system, the big seems to have no scope, that is, it is layered.
The largest known galaxy
Going back to the starting point, from the perspective of the Milky Way, its diameter is about 100,000 light-years, which is ridiculously large on a human scale. But among the galaxies of the universe, the Milky Way is a little brother.
Astronomers have discovered the largest galaxy currently known in the universe, which is 153 times the diameter of the Milky Way. The galaxy, named Alcuonus, is more than 16.53 million light-years in diameter.
To put it simply, for example, the Milky Way and this galaxy are division-level units, and the Milky Way only has a basic number of about 3,000 people, while the latter is fully equipped with between 10,000 and 15,000 personnel.
Behind the size of a galaxy is essentially the size of its gravitational pull accumulating. And the galaxies themselves are in motion, and each galaxy has the potential to merge, thus forming larger galaxies.
epilogue
From the overall structure of the universe, it can be seen that between the big and the small, between the moving and the immobile, there is a relationship between the microcosm and the macrocosm everywhere.
In current perception, the Great Wall is the largest of the largest, and it seems to be immovable as a whole. And perhaps one day in the future, new understandings and discoveries of the universe will break the current level. It seems that there is no end to exploring the universe, only infinity.
Resources:
"The Boundary of the Universe Appears in Bojiangzuo, Do You Think Too Much", Science and Technology Daily, November 29, 2018
"Astronomers discover that the largest galaxy in the universe is 150 times the diameter of the Milky Way" Reference News Network March 7, 2022