Before human beings go out of the earth, we only know that the world is very big, but we don’t know how much it is. On the earth, any object has shape, square circle, circle and other irregular shapes.
Since all the materials in the world have shapes, the earth made up of them naturally has shapes. However, for the ancients, they did not know the shape of the earth at all. When we were on the earth, it was difficult for us to really see what the earth looked like. Only when human beings enter the era of science and technology, with the help of science and technology out of the earth, we really know the shape of the earth: a closed three-dimensional sphere.
Standing in space, we can easily see the shape of the earth, it is a sphere, and also found that other planets in the universe are also presented as spheres. Although scientists have conjectured that a kind of ring planet can exist in theory, we have not observed such a shape of planet in the universe.
In addition to planets, most of the other celestial bodies also appear as spheres. Only a few small celestial bodies may show some irregular shapes. The larger the celestial body is, the rounder it will be. The reason why celestial bodies are basically spherical in shape may be determined by gravity.
When people walk out of the earth, they know that the shape of the earth is a sphere. At the same time, scientists are also thinking about such a question: what is the shape of the universe? Although some scientists think that the universe has been expanding, it is boundless and has no fixed shape, most scientists still think that the universe can not be infinite, and it is unlikely to have no shape.
So what is the shape of the universe? Scientists also have different views on the shape of the universe. Some scientists believe that even if the celestial bodies in the universe are basically spherical, the universe composed of numerous celestial bodies may also be a huge closed three-dimensional sphere. Some scientists believe that the universe may be an infinite flat three-dimensional space, or a three-dimensional saddle surface.
Which of the three conjectures about the shape of the universe put forward by scientists is correct? To understand this problem, we have to deal with a key number that determines the shape of the universe: the critical density of the universe. For the endless exploration of the universe, we have to thank a great scientist, he is Einstein.
After Einstein applied the principle of cosmology to the study of cosmology, his theory of relativity plays a more and more important role in the exploration of the universe. According to Einstein’s cosmology, the shape of the universe is strictly limited, and every point in the universe has equal status. Therefore, there are only three possible shapes of the universe: one is a closed three-dimensional sphere, one is a flat three-dimensional space, and the other is a three-dimensional saddle surface.
According to Einstein’s general relativity, the curvature of the universe depends on the distribution of matter field in the universe. Therefore, as long as we measure the distribution of material sites in the universe, we can infer the shape of the universe.
If the cosmic space has positive curvature, then it is a closed three-dimensional sphere; if the curvature of the cosmic space is zero, then it is a boundless flat three-dimensional space; if the cosmic space has negative curvature, then it also has no edge, it is a three-dimensional saddle surface.
. In a new paper published in nature astronomy, Eleonora Valentino of the University of Manchester, Alessandro Melchio of the University of Sapienza in Italy and Joseph Silke of the University of Oxford calculated the curvature of space as positive according to the gravitational lens amplitude in the power spectrum of the cosmic microwave background radiation of the satellite. In other words, space is a closed three-dimensional sphere.
The so-called three-dimensional sphere can also be connected with the famous Poincare conjecture in mathematics. Poincare conjecture holds that there is only one simply connected three-dimensional geometry without boundary, and the only possibility is three-dimensional sphere. So, if Eleanor Valentino’s paper is correct, then we can link the Poincare conjecture with the shape of space, which has a theoretical beauty.
Of course, the latest research on the shape of the universe is only a possible conjecture. It may be difficult for us to detect the shape of the real universe. The Hubble constant is used by scientists to explore the shape of the universe. However, at present, the value of the Hubble constant is still uncertain, and there are great differences between different methods. Since the Hubble constant is uncertain, the average density of the universe is also uncertain, so the critical line is fuzzy. Therefore, it is too early to say that the universe must be closed.
Although we still can’t determine the specific shape of the universe, the recognition that the universe has boundaries is supported by more and more scientists. We can imagine the universe as a balloon that can keep expanding. This balloon has a specific shape and obvious boundary, but it has no definite diameter and volume. The reason is that the balloon is always expanding and the diameter and volume change at any time.
The situation of the universe may also be the same. If it is a closed three-dimensional sphere, it also has a specific shape and obvious boundary. However, due to the effect of dark energy, it has been expanding outward and has no fixed diameter and volume.
The current observable range of human beings is 92 billion light years. If the observable area is defined as a small universe, then the universe is an ideal sphere with the earth as the observation center and a radius of 46 billion light years. Of course, this is only the observable range of human beings, not the whole universe. There is a huge gap between the two.
The scope of the universe that can be observed by human beings may only be a point in the whole universe, just like galaxies and stars under the cosmic scale. They are very large in our opinion, but they are only a point in the cosmic scale. The universe is formed by the interaction of countless such points. In fact, although we have no ability to really get the real shape of the universe, the universe is a sphere, which has been recognized by many people.
It is possible that with the continuous progress of human science and technology, we will explore the universe more widely in the future, and there will be more advanced methods to detect the shape of the universe. However, if we really want to know the specific shape of the universe, the best way is to go to the edge of the universe, or even out of the universe. If we can go out of the universe and stand outside the universe, we believe that the shape and true face of the universe will also appear before our eyes.
Of course, if human beings really go out of the universe in the future, it will be a new beginning. For example, before and after human beings go out of the earth, their cognition and vision are totally different, which is a sublimation of human civilization. And the next sublimation of human civilization may be the day when we walk out of the universe. Maybe at that time, we will also sigh that the universe in which human beings live is just a grain of dust.
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