The famous scientist Einstein proposed many scientific hypotheses during his lifetime.
Among them, the hypothesis about black holes was questioned by countless people at that time when astronomical technology was not yet developed. However, with the successful shooting of black hole photos in recent years, the existence of black holes has been truly and thoroughly confirmed.
Of course, is similar to a black hole. During his lifetime, Einstein also predicted the existence of another "cosmic extreme", which is wormhole .
Most of the interstellar and time travel scenes in science fiction movies are achieved through traveling through wormholes. If wormholes really exist, then we will have a way "faster" than the speed of light. We only need to pass through it. Can reach the edge of the universe in an instant.
But the question is, do wormholes really exist?
About black holes and white holes
In order to figure out what a wormhole is, it is necessary for everyone to first understand the relevant knowledge about black holes and white holes.
Let’s first talk about what is black hole . From a physical point of view, black hole is actually a celestial body with extremely large mass density. However, its mass density is so large that the space and time near it are seriously affected. Let space-time curvature be so large that even light cannot escape.
This is also the fundamental reason why a black hole is called a black hole, because it can "swallow" even light. Without any light reflection , it appears in front of our eyes. A black hole is a "pitch black" existence. .
Space-time distorted by black holes
Speaking of black holes, Okawa has to mention the first black hole photo released by scientists on April 10, 2019.
According to scientists' calculations, the mass of the black hole (M87*) in the photo is at least 6.5 billion times the mass of the sun, and its volume is at least 6.8 million times that of the sun.
Due to the special physical properties of the black hole, its existence cannot be directly observed. Therefore, scientists used the Event Horizon Telescope (EHT) to observe and photograph it. The light around the black hole we see in the photo is not emitted by the black hole itself, but by the black hole devouring the surrounding celestial bodies. The huge energy released by these celestial bodies in the process of being devoured is transmitted in the form of light. Come out, and this is the black hole we see before our eyes.
If we had not swallowed the celestial bodies at that time, I am afraid we would not be able to see this monster wandering in the universe...
There are many black holes like M87* in the universe. You may find it incredible to say that Even us The center of the Milky Way is actually a huge black hole. Scientists call it the Galactic Center Black Hole (Sagittarius A* (Sgr A*)).
This black hole is about 26,000 light-years away from the earth, has a diameter of about 44 million kilometers, and its mass is conservatively estimated to be about 4.1 million times the mass of the sun.
The large mass is not the scariest thing about a black hole. The scariest thing about a black hole is its terrifying devouring ability. We all know that for celestial bodies, the greater the mass of the celestial body, the greater the gravity. Because according to the law of universal gravitation formula (F=GMm/r²) , gravity is proportional to the mass of the celestial body, so black holes The gravitational force is quite large, which further causes the black hole surface to have an extremely high escape velocity, and this escape velocity is greater than the speed of light of 300,000 kilometers per second.
Based on this escape velocity, any celestial body approaching a black hole will be captured by the black hole's gravity as long as its speed is less than the speed of light, and will eventually become the "food" of the black hole. Being swallowed by the black hole is called part of the black hole's mass. Even if it is light, There is no way to escape the fate of being swallowed by a black hole.
Let’s talk about white holes . White holes are actually another “cosmic extreme” predicted by general relativity .
In terms of physical properties, a white hole is a celestial body that is completely opposite to a black hole. You can understand that a black hole is an existence that infinitely swallows surrounding celestial bodies. This is equivalent to a kind of "attraction", while a white hole is The existence of unlimited release of matter and energy is equivalent to a "repulsive force".
However, it is worth mentioning that although the existence of black holes has been completely confirmed, white holes are still a hypothetical celestial body , and scientists have never conducted actual research and discovery on their existence.
What is a wormhole?
After clarifying the black hole and the white hole, it should be easy for everyone to understand the wormhole.
The concept of wormholes was first proposed by Austrian physicist Flem in 1916. It was later supplemented and improved by Einstein and Nathan Rosen, and the current wormholes (Einstein Stein-Rosen Bridge) concept of .
Regarding wormholes, there is a widely accepted theory. It is a channel that connects black holes and white holes (also known as "grey lanes" ). Matter is infinitely sucked and swallowed by the black hole, and then passes through the middle. This passage enters the white hole and erupts infinitely from the white hole. The existence of the "bridge"
also explains the possibility of the existence of white holes.
Why can we "arbitrarily" travel through time and space through wormholes?
Okawa mentioned earlier that the mass density of the black hole is so huge that the space-time near it is greatly compressed, and the curvature of space-time is so great that even light cannot escape.
In this context, the existence of black holes has become a "portal" through time and space. Since the curvature of space and time near the black hole is very large, when we are near the black hole, the relationship between time and space on the earth is The rules no longer apply. A segment in the science fiction movie "Interstellar" perfectly restores this characteristic of black holes.
After the male protagonist came out of the black hole and returned to the earth, his daughter turned into a gray-haired old man, but he himself still maintained the same appearance as when he entered the black hole.
The male protagonist visits his daughter after returning to the earth from the black hole
In other words, Although time passes normally after he enters the black hole, due to the different curvature of space and time, compared to his daughter on the earth, his time actually tends to stand still , you can understand it as the phenomenon of "one day in the sky and ten thousand years on the earth".
Based on this, if wormholes really exist, as long as we can successfully enter from the black hole, we will definitely be able to travel through time and space.
Here, time is not a problem, and distance is not a problem .
has a black hole as the entrance. You can simply understand that the infinite curvature of is equivalent to infinitely compressing the distance. Although the speed of spaceship does not change when traveling in it, it is accelerating infinitely relative to the starting point. The curvature engine that is standard on spaceships in many science fiction movies is conceived based on this principle.
Curvature engine spacecraft schematic
It is precisely for this reason that if wormholes really exist and we master the method of entering wormholes, then we will get "faster" than the speed of light, and even reach the edge of the universe in an instant can be achieved theoretically.
is written at the end
At the end, Okawa needs to add one more point about the topic of time travel through wormholes.
That is, through the wormhole we can only go to the future time, but cannot go back to the past . And not only wormholes cannot take us back to the past, it is also impossible for any device that travels through time and space to take us back to the past, because it will involve a terrible paradox - the grandfather paradox .
A went back in time and killed his grandfather before he got married and had children. If A's grandfather died, A's father could not have been born, and A could not have been born without his father.Since A was not born, who killed A's grandfather?
Obviously, this is a paradox that does not make sense and is impossible...
