Time-space traveler event [various conditions of human time-space travel]

Time travel refers to the movement of people or other objects from one time point to another. In the existing concept of human beings, all people advance naturally with time. This so-called time travel violates the law of natural time change, and its end point is either going to the future or going back to the past to realize time travel.

Time travel and relativity

For thousands of years, from the ancient Indian epic Mahabharata to Herbert? George? Wells's science fiction The Time Machine embodies people's yearning for time travel in different periods. However, in ancient times, human beings did not make a theoretical analysis of time travel, and all kinds of time travel imaginations were mixed with folk stories and myths. After entering the 20th century, with the development of science and technology, theories about time travel began to be enriched, among which Einstein's special theory of relativity and general theory of relativity are the most famous.

Einstein realized that galilean transformation was actually the embodiment of Newton's classical concept of time and space. If we accept the experimental fact that the speed of light in vacuum has nothing to do with the reference system as the basic principle, we can establish a new concept of time and space (relativistic concept of time and space). In this view of time and space, Lorentz transformation can be deduced from the principle of relativity. In 2005, Einstein published a paper on electrodynamics of moving objects, put forward the special theory of relativity, and successfully described the motion of macroscopic objects in sub-light velocity field. Time dilation in deduction (assuming that all physical and chemical changes will slow down when an object moves, that is, time dilation, referred to as time dilation) is also called Einstein delay. The slow time hypothesis holds that the clock carried by an object with uniform motion is measured by the clock of a stationary observer, and the moving clock slows down with the increase of the motion speed, regardless of the motion direction.

Relatively speaking, Einstein's general theory of relativity is more important to the concept of time travel. In general relativity, gravity is described as the geometric property (curvature) of space-time; This curvature of space-time is directly related to the energy momentum tensor of matter and radiation in space-time, and its connection is Einstein's gravitational field equation.

The method of realizing time-space travel

It is generally believed that there are three ways to go back to the past, namely, superluminal travel, using cosmic strings and black holes, using wormholes and Akubbery engines.

In the theory of relativity, if the speed exceeds the speed of light, time to go back will appear, but now some scientists think it is impossible to reach or exceed the speed of light. The use of cosmic strings and black holes is just fake. First of all, cosmic strings are theoretically possible spacetime. Moreover, the mass of the black hole is quite large, and the gravitational field generated is very strong. No matter and radiation can escape, and even light cannot escape. How do humans use black holes to make time to go back?

In this way, there are only three methods to choose from: wormhole and Akuberi engine. Wormhole, also known as "Einstein-Rosen Bridge", is a narrow tunnel that may exist in the universe, connecting two different time and space. 19 16, Austrian physicist Ludwig? Flem first put forward this concept, and then Einstein and Nathan put forward this concept in the 1930s. When Rosen studied the gravitational field equation, he concluded that the spatial transfer of instantaneous time or time travel can be completed through wormholes. Although scientists have not found evidence of the existence of wormholes so far, the concept of "Einstein-Rosen Bridge" has been accepted by more and more people. Hawking, a famous scientist, also thinks that wormholes are the key to time travel in his classic book A Brief History of Time. As long as there is huge energy to open the wormhole, time travel can be realized.

Aku Bieri engine is a detailed spatio-temporal mathematical model, which often appears in papers of foreign physics journals. It follows Einstein's equation in general relativity, and obtains a special space-time measure in this category. 1994, physicist Miguel? Akubri proposed to use waves to expand the space, which led to the space in front of the plane (referred to as "ship") shrinking and the space behind it expanding. The axial direction before and after the connection is the direction in which the ship will sail. The spacecraft braved the wind and waves in an interval called warp bubble, which is a flat space-time. Because the spacecraft does not really move in the warp bubble, but is carried by the warp bubble, it is useless to limit the speed of an object in general relativity not to exceed the speed of light. A few days ago, scientists didn't know how to trigger such fluctuations, or how to leave once triggered. Therefore, the Akubri engine is still in the theoretical concept category.

In recent years, a concept of time travel has emerged, completely abandoning the theory of relativity. This theory is suitable for exploring the future world, but it has also been strongly criticized by all walks of life. This is the controversial "life pause" theory, that is, through external forces (such as medical technology) to slow down the life process to almost pause signs; But in fact, life is not dead, heartbeat and breathing can still exist, but they can only be measured by machines. Western media believe that this method can enable human beings to visit the world hundreds of years later. Since 2005, western countries have carried out a series of such experiments. In July 2005, scientists conducted experiments on several dogs. They took out the dog's blood and injected frozen protective solution into their circulatory system, trying to save their lives when the blood flow stopped. After three hours of clinical death, scientists reinjected the dog's blood into their circulatory system and used electric shock to restore their heartbeat. In this experiment, most dogs recovered successfully, but a few dogs suffered brain damage. From June 5438 to October 2006 10, scientists successfully conducted experiments on pigs, with a success rate of 90%.

But the question is, who among human beings is willing to suspend life, leave the familiar real society and wait for decades or hundreds of years to recover? Furthermore, by "stopping life", you can only go to the future, but you can't go back to the past.

Paradoxes of time and space travel

It is true that even if the future conditions are ripe, time travel still faces many challenges. 1943, French science fiction writer Ernee? Bach Zaweiler put forward a hypothesis in the novel The Careless Traveler that if you went back in time, you would kill your grandparents before your father was born. In this way, if your grandparents die, there will be no father; Without your father, you wouldn't be born; No one will kill your grandparents before you are born; If no one kills your grandparents, you will exist and go back to the past. If you kill your grandparents, contradictions will arise. The above is the famous "grandfather paradox" that we have to face in time travel.

Physicists believe that the "grandfather paradox" has its own solution. They concluded that the world may be composed of countless parallel universes. When you summon the past to kill your grandparents, you actually kill people in another universe, and your behavior may create a new parallel universe. The death of your grandparents will only make you in the parallel universe cease to exist, and you in this parallel universe will be safe.

Specifically in quantum physics, the theory of "multiple worlds" can be understood as follows: for every seemingly random event, as long as its possibility is not zero, all possible situations will occur in different parallel worlds, thus producing a branch of history. Physicist David? Deutsch believes that when you go back to the past and kill your grandparents, you have actually entered another world and killed people in another world. Besides, the only difference between that world and yours is that your grandparents have passed away.

In today's world, it is most likely to combine five different string theories-M theory to explain the parallel universe as follows: a four-dimensional universe can have multiple three-dimensional films at the same time (not Einstein's two-dimensional space plus one-dimensional time, but the universe actually embeds some higher-dimensional films); The collision between these films can generate a lot of energy in the films-which can also explain how BIGBANG originated. But M theory can't explain the relationship between the history of different movies, and it can't be sure that when you go back to the past, you will enter another movie.

Contrary to the "grandfather paradox", there is a "fate paradox", which shows that time travel is extremely dangerous. The paradox of fate holds that if you go back in time and kill your grandfather, then your father will not appear. Simply put, you will disappear from the torrent of time. The paradox of fate is also called causal cycle. Its concept that historical facts are not affected by changes made in time and space travel is that the practice of changing history, regardless of its intention, will eventually lead to the "fate" result of history, but it cannot be changed beyond it.

There is a famous example of fate paradox in the history of China. Li, an astronomer in the Tang Dynasty, wrote a secret book, which said, "The weak in the Tang Dynasty had a female king of Wu." Li predicted that the marquis of Wu would be proclaimed emperor, and if forced to change, there would be unexpected consequences. Inadvertently, Li Shimin, Emperor Taizong, learned the news. He killed a general who was suspected to be a "female warrior", but Wu Zetian, who would really be the emperor of the Tang Dynasty, was not killed. This means that going back to the past cannot change the historical development process of our world.

Since there is a paradox of going back to the past, there is naturally a paradox of going to the future world. Corresponding to these two paradoxes is the "prophetic paradox": that is, when you come to the future, you know the unfortunate results that will happen; Now that you have taken actions to avoid leading to result A and eventually leading to result B, then result A will never happen in the future. How do you know result A? The paradox that A and B can't satisfy. )

It is true that there are too many unsolved problems about time travel at the current scientific level of mankind, but this does not mean that time travel is just a theory. In some documents decrypted today, you may be able to see the shadow of time travel.