After a short break, they started a new study, this time they shifted their goal to the study of space-time wormholes, which Hua Feng was more interested in.

A space-time hole (also known as the Einstein-Rosen Bridge) is a narrow tunnel in the universe that may exist connecting two different space-times.

The concept of wormhole was first proposed by Austrian physicist Ludwig Flaim in 1916, and hypothesized by Einstein and Nathan Rosen in 1930 when studying the gravitational field equation, that instantaneous space transfer or time travel can be done through wormholes.

The theory was developed by Albert Einstein. To put it simply, a "wormhole" is a thin tube of space-time that connects distant regions of the universe. Dark matter keeps the wormhole exit open. Wormholes can connect parallel universes to baby universes and offer the possibility of time travel. A wormhole may also be a space-time tunnel connecting a black hole and a white hole, so it is also called a "gray tunnel".

Theoretically, a wormhole is a spatial tunnel connecting two distant space-times, like a whirlpool in the sea, which is ubiquitous but fleeting. These space-time vortices are caused by a combination of star rotation and gravity. Just as a whirlpool can bring a local water surface closer to the bottom of the water, two local spaces that are far apart can instantly get closer together.

The concept of "wormhole" was first proposed by Austrian physicist Ludwig Flem in 1916 and perfected by Albert Einstein and Nathan Rosen in 1935 [1], so the "wormhole" is also known as the "Einstein-Rosen Bridge". In general, the "wormhole" in people's mouth is the abbreviation of "space-time wormhole", which is considered to be a possible "shortcut" in the universe, through which objects can be transferred in time and space in an instant. However, Einstein himself did not believe that "wormholes" existed objectively, so "wormholes" were considered to be just a "mathematical trick" in later decades.

In 1962, Robert Fuller and John Wheeler published a paper proving that wormholes are unstable if they connect two parts of the same universe. In 1963, New Zealand mathematician Roy Kerr proposed a hypothesis that regained theoretical support for the existence of "wormholes" [1]. Like humans, stars go through a process of birth, aging, sickness and death, and Kerr believes that if stars can keep rotating as they approach death, they will form the "dynamic black holes" we see in movies. When we launch an object along an axis of rotation like in the movie, if we can break through the gravitational field limit at the center of the black hole, we will enter the so-called "mirror universe". The "extradimensional" space in which the astronaut Cooper in "Interstellar" is located in a black hole can actually be seen as an interpretation of the "mirror universe". Entering the "mirror universe" from the universe is itself a "time and space travel".

The "Milky Way wormhole theory" originated from the breakthrough in dark matter research. Dark matter is a substance that does not interact with electromagnetic forces and cannot be studied through the observation of electromagnetic waves. Unlike "wormholes", gravitational effects have confirmed the existence of a large amount of dark matter in the universe. In 2013, the research team of the International Institute for Advanced Study in Trieste drew a very detailed map of the dark matter distribution of the Milky Way, and after combining it with the latest research of the Big Bang model, it was found that not only does the Milky Way have the conditions for the existence of "wormholes", but even the entire Milky Way may be a huge "wormhole".

According to the theoretical model established by the Italian astrophysicist Paolo Salucci and others, such a hypothesis is indeed possible to be confirmed [1], and its greater significance lies in the fact that it will prompt scientists to "rethink more accurately" the study of dark matter: is dark matter the existence of "another dimension", or is it itself a transportation system for interstellar transportation?

The "wormhole theory" is still a hypothesis at present, but scientific progress is inseparable from bold hypotheses [1]. At one time, it was thought that the smallest unit of matter was the atom, and later neutrons and protons were discovered. Similarly, for a long time, humans believed that the universe was made of matter, but the existence of dark matter has overturned this conclusion. The significance of scientific hypotheses is to get rid of existing shackles and advance human understanding of the universe and their own progress through constant self-denial and doubt. As Sarucci puts it, "In any situation, we need to ask ourselves, what is it?"

The concept of wormholes was first developed in the study of Schwarzschild solutions. When theoretical physicists analyzed the solution of the white hole, through an Albert Einstein thought experiment, they discovered that the universe itself could not be flat. If a star forms a black hole, then space-time is perpendicular to the original space-time in the Schwarzschild radius, which is the event horizon. In the uneven space-time of the universe, this structure means a black hole.

The part within the horizon will combine with another part of the universe and create a hole there. This hole can be either a black hole or a white hole. And this curved horizon is called Schwarzschild throat, and it is a specific kind of wormhole.

Ever since the discovery of wormholes in Schwarzschild solutions, physicists have become interested in the nature of wormholes.

The wormhole connects the black hole to the white hole, and is transported between the black hole and the white hole through this wormhole (i.e., the Albert Einstein-Rosen Bridge) to the white hole and is radiated out.

Wormholes can also manifest in the normal space-time of the universe, becoming a superspace-time that suddenly appears. There are also many characteristics of the wormhole introduced by the theory, which will not be repeated here due to space limitations.

In short, we still know very little about the nature of black holes, white holes, and wormholes, and they are still mysterious things, and many questions still need to be further explored. Astronomers have indirectly found black holes, but white holes and wormholes have not really been discovered, and they are just a theoretical term that often appears in science fiction works.

In the universe, the "cosmic term" is almost zero. The so-called cosmic term is also called "the energy of the vacuum", and in the absence of matter, energy also exists.

Inside, this was imported by Albert Einstein. In the early expansion of the universe, the cosmic term was necessary, and in the theory of elementary particles, it was also believed that the energy in the vacuum was naturally presented. Coleman explained that in the early universe before the explosion, wormholes were connected to many universes, and the size of the universe terms was cleverly adjusted to zero. As a result, one universe may give rise to another, and there may be an infinite number of such tiny caverns in the universe that lead to the past and future of one universe, or to other universes.

Even if wormholes exist and are stable, walking through them can be very unpleasant. Radiation through the wormhole (from nearby stars, the microwave background of the universe, and so on) shifts the blue to very high frequencies. When you try to walk through the wormhole, you will be scorched by these X-rays and gamma rays. The appearance of wormholes can almost be said to be at the same time as black holes.

If you stand at one end of the wormhole (entrance) at 12:00, you will come out of the other end of the wormhole (exit) at 12:00.

Wormholes, also known as the Einstein-Rosen Bridge, are narrow tunnels that may exist in the universe connecting two different space-times.

Albert Einstein's thought experiments revealed that space-time in the universe itself could not be flat. In the uneven space-time of the universe, this structure means that the part within the black hole's event horizon will combine with another part of the universe.

Wormholes connect black and white holes, transporting matter between black and white holes. Here, the wormhole becomes an Albert Einstein-Rosen bridge, where matter is completely disintegrated into elementary particles at the singularity of the black hole, and then transported through this wormhole (the Albert Einstein-Rosen Bridge) to the white hole and radiated out.

Wormholes can be used as a chrono conduit, and can also manifest in the normal space-time of the universe.

The wormhole has no horizon, it only has a sub-interface with the outside world, through which the wormhole is connected in time and space. The interface between the wormhole and the black hole and the white hole is a space-time pipeline and a connection between two space-time closed regions, where the curvature of space-time is not infinite, so we can safely pass through the wormhole without being destroyed by the huge gravitational force.

Black holes, white holes, and wormholes are still unsolved mysteries in the "space-time and gravitational chapter" of current cosmology. Whether black holes really exist or not, scientists have only obtained some indirect circumstantial evidence. Current observations and theories have also raised many new questions for astronomy and physics, for example, when a cold star that can form a black hole collapses, its density will already exceed that of atomic nuclei, nucleons, and neutrons...... If it continues to collapse, the neutrons may also be crushed. So, what exactly are the material primitives in a black hole? What is the repulsive force and gravity that causes the black hole to stay at a certain stage and not continue to collapse? If there is no repulsion, then the black hole will collapse infinitely until the volume is infinitely smaller, the density is infinite, and the internal pressure is infinite, which is not allowed by physical theory.

In today's universe, there are almost zero "cosmic terms".

Physicists have long believed that the gravitational pull of a wormhole is so great that it destroys everything that enters it, so it cannot be used for space travel. However, if there is such a thing as a wormhole in the universe, then there can be a saying: if you stand at one end of the wormhole (entrance) at 12:00, then you will come out of the other end of the wormhole (exit) at 12:00.

Wormholes, also known as the Einstein-Rosen Bridge, are narrow tunnels that may exist in the universe connecting two different space-times.