What is the end of the universe?

Before Columbus and da Gama completed their round-the-world voyage, navigators had a lingering nightmare, that is, they would suddenly sail to the end of the world and fall into an endless abyss. The idea was so strong that both navigators got constant advice before setting sail! But it turns out that the world has no end, because the earth is a sphere in three dimensions, and we can't find its boundary on its surface!

But people on the International Space Station can clearly see where the boundary of the earth is. The fear of the end of the world in history is nothing more than the limitation of understanding the earth!

So does the universe have boundaries? Where does it end?

In Ptolemy's expanding geocentric theory, the outermost celestial body is the star sky, but outside the star sky, Ptolemy left this position to God, so from 1800 BC to16th century BC, the church liked this geocentric theory very much, because they left a position for God, which made the church put God in the right position while preaching geocentric theory!

Ptolemaic geocentric theory

But everything vanished in front of Copernicus, because Copernicus learned that the Heliocentrism proposed by Aristakes, an ancient Greek mathematician in 300 BC, was very reasonable, and through his own rigorous observation, he proved that the sun is the center of the universe, and the stars in the sky revolve around the sun, so there is no longer a place for God, so Heliocentrism was madly suppressed by the church. But Copernicus survived because "an old fox" published Heliocentrism.

Whether the church suppressed it or not, Heliocentrism grew like a weed, while Kepler and Galileo strengthened Heliocentrism from observation, Newton formulated the gravitational rules of celestial bodies, and Laplace initiated celestial mechanics in the celestial bodies in the solar system. From the end of the eighteenth century to the beginning of the nineteenth century, more than a dozen books of Celestial Mechanics were published, which made Laplace face Napoleon and ask "Where is God in your theory?" Laplace replied, "Your Majesty, mine.

From this day on, there is no God at the boundary of the universe. Newton's early speculation that the universe is infinite and Olbers's paradox both show that the universe is infinite and has a starting point, but it is not mature in theory and cannot prove this view.

The shape of the universe

No one can observe the shape of the universe, even now! But Einstein's general theory of relativity published in 19 15 made all this possible. 19 17 years, Einstein himself applied general relativity to cosmology and gave birth to relativistic cosmology. But in order to cater to the static view of the universe at that time, the lovely Einstein added a cosmological constant to the dynamic universe he discovered by using the gravitational field equation and revised it into a static universe!

In the independent state of Friedman and Lemaistre, an extended universe option without cosmological constant is obtained by applying the isotropic hypothesis, namely friedmann equations. Howard P. Robertson and Volcker respectively proved in 1935 and 1936 that there are only three kinds of four-dimensional spacetime suitable for uniformity and isotropy, namely Friedman-Robertson-Walker metric, and the shape of the universe depends on a space curvature K.

Friedman-Robertson-Walker metric

The most critical parameter in this measurement is k, and its value determines the shape of the universe. If we don't discuss the fate of the universe today, we won't talk about the relationship between the cosmological constant λ and the value of k, because the determination of the cosmological constant λ needs the comparison between the critical density and the actual density as a substitute. Due to the limitation of space, I directly use the condition that the flat universe observed by the modern universe is K=0, combined with the observation of the red shift of the Ia supernova by two international astronomical teams in 1998, and come to the conclusion that the universe is accelerating.

When K=0, the three-dimensional universe is flat and the space is infinite. According to the theory of accelerated expansion, the future fate of the universe is embarrassing. It can be concluded from this point that the universe has no boundaries and is an infinite region!

What is the end of the universe?

In fact, we don't need to discuss the end of the modern universe, because the infinite universe has no boundaries. Of course, in theory, we can assume a boundary. For example, when the curvature K= 1, the universe is a three-dimensional sphere, so can we find its boundary in this spherical universe? What will happen in the end?

At one time, all the members of Stargate-Universe had to go to sleep, because Destiny had to cross an unimaginable vast space, and it had to use all its energy on the engine, and there was no star to supplement the energy on the way. The florist guessed that crossing this area would penetrate the microwave background radiation until the moment of the big bang!

However, the Stargate-Universe has been off the air for more than ten years. Many stargate fans are eagerly looking forward to seeing the end of the universe from the perspective of Hollywood. Unfortunately, we may never see it, but it doesn't matter. We can speculate on the end of the universe in our own way.

What is the boundary of the universe like?

Maybe we can't see the boundary of the universe at all, because BIGBANG thinks that there are big explosions in time, space and matter, so the boundary of the expansion of the universe is the boundary of time and space, and there is no space in a chaotic region with nothing. How can we perceive it? The biggest possibility is an unbounded area with edges like the earth. We know its size, but we don't know where its boundary is!

How to understand chaos?

Perhaps it is a state with lower energy than vacuum, because quantum mechanics believes that there are quantum fluctuations even in the empty state. According to Heisenberg's uncertainty principle, the more accurate the time t is measured, the more uncertain the energy e is. At the moment when time t is very certain, there will be huge energy fluctuations in the vacuum! So chaos may be a real vacuum, it has no quantum fluctuations, and it is in the real lowest energy level!

The real boundary of the universe

It may be more appropriate to describe the vacuum attenuation region. In a general vacuum, energy does not decay and remains stable. If you want to enter the chaotic region of vacuum decay, you may need to apply extremely high energy to cross it. But after crossing the gap of this energy barrier, according to the principle of minimum energy, all substances that penetrate this barrier will decay into a real vacuum, which is the real endless abyss! But so far, we can't reach this energy, so we can't cross this border!