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On the road of human science and technology development, many great physicists have appeared, such as Newton , Einstein , Hawking , Schrödinger , Galileo , etc. These great physicists have played a vital role in the development of human science and technology. The once famous physicist Einstein believed that time does not exist. He believed that if human beings can fly at the speed of light, then time will stop. If human beings can fly faster than the speed of light, then time will flow backwards. What is time? I believe that each of us is very familiar with time. After all, we deal with time every day, but few people can explain what time is. Time exists objectively and is not transferred by human consciousness.
And time and space must appear at the same time. If you leave aside space and discuss time alone, then time will become meaningless, because time, space and space cannot be separated. Einstein believes that time is a manifestation of material movement change, and space is the manifestation of material existence. Time and space are combined It has become the four-dimensional space we are in. We call it space-time for short. Time and space are not static. Einstein believed that time and space are relative, space-time is elastic, and speed and gravity can affect time and space. In special relativity , time can produce expansion and contraction effects. Simply put, the faster the speed of an object, the slower time will become.
For example, if we leave the earth in a light-speed spacecraft at sub-light speed, the time on the spacecraft will become slower and slower compared to people on the earth. If the spacecraft has been flying in the universe for 10 years, but for people on the earth, 100 years may have passed. If our spacecraft can exceed the speed of light, then time will flow backwards. In this case, if humans go back to the past through time travel, You will face an unsolvable problem. This problem is the grandfather theory. The grandfather theory was proposed by French science fiction novelist Henri Bach Zavelle. He believes that if you can go back in time and kill your grandfather before your father is born, this action will produce a series of contradictions. If you go back in time and kill your young grandfather, then your grandfather will not give birth to your father, and your father will not be able to give birth to you. Since you do not exist, then how do you kill your grandfather?
The grandfather theory has always been a topic of constant debate among scientists. There are currently two explanations in the scientific community about the grandfather theory. The first is the parallel universe theory. Scientists believe that when we start time travel and go back to the past, we actually travel to another parallel universe . Scientists believe that in our There is not only one universe, but many universes. Each universe is an independent individual, but each universe is like a mirror. There are the same things in different universes. For example, in our universe you are a doctor, but in another parallel universe, you may be a teacher or a scientist. Simply put, your life has countless possibilities.
If we kill our young grandfather, then in this parallel universe, our father will not be born, and we ourselves will not exist, but this does not affect our original universe, because in our original universe, both grandfather and father exist. If parallel universes really exist, then the grandfather theory can be perfectly explained. However, parallel universes are currently just a speculation put forward by scientists. Do parallel universes really exist in the universe? Scientists now have no accurate answer. In addition to this explanation, the scientific community has another explanation, that is, people can go back to the past, but there is no way to change history.
When we go back in time, we can only watch what happened in the past as bystanders, but we cannot do anything in the past time. However, there are also conditions required to achieve time travel. In our three-dimensional world, for an object to move from another place to another, it only needs to meet three basic conditions. The first is transportation. The second is speed, and the third is time. According to Einstein's theory of relativity, we know that high-speed motion can produce a time dilation effect. If a spacecraft moves at the speed of light, a day on the spacecraft is equivalent to one year on the earth. If the spacecraft flies at the speed of light and returns to the earth, then three hundred years have passed on the earth. To achieve time travel, we must find a tunnel that can travel through time and space.
In Einstein's theory of relativity, there is such a mysterious celestial body. This celestial body is a wormhole. A wormhole is a tunnel that can travel through time and space. If we can enter a wormhole, we can travel to a long distance in a short time. Many scientists believe that a black hole may be the entrance to a wormhole. The nature of a black hole is to continuously swallow matter. Where does the matter swallowed by the black hole end up? Scientists believe that there is a mysterious celestial body white hole at the other end of the black hole. Black holes and white holes are connected together to form a wormhole. A wormhole is a tunnel that can travel through time and space. At present, humans have discovered black holes in the universe, but white holes and wormholes are still in theory. If we find a wormhole, will we be able to achieve time travel?
In fact, each of us hopes that time travel can be realized, because in our past lives, there were many things we did not ideal at the time. For example, you met the person you liked most at the most suitable time, but you did not have the courage to confess your love at the time, and ultimately missed this opportunity, resulting in you not having Together, if time travel can be achieved, then you can go back to the beginning, make a bold confession, and maybe the other party can accept you. In addition to this regret, there are many people who regret it for life because of doing wrong things or making wrong decisions. If we can use time travel to change the past, then there will be no regrets in our lives, but can time travel really be realized? In existing physics, time and space have been perfectly explained. These two concepts are actually abstract concepts that we refer to when describing the physical world in front of us.
To put it simply, when we describe moving from one point to another, we use the concepts of space and time. How far we move in space, it takes the same amount of time. Although time travel is theoretically possible, it violates the second law of heat - the law of entropy increase . According to the law of entropy increase we can know, Heat can move from high temperature to low temperature, and this process is irreversible. Time travel violates this law. If we go back in time, it means that the time you are in has gone backwards. In contrast, entropy decreases, but the entropy in this universe cannot be decreased, so time travel cannot be realized. The law of entropy increase was proposed by the famous physicist Schrödinger in 1943. He believed that life depends on negative entropy. After this sentence was proposed at that time, many people did not understand it.
He believes that in a limited space, the temperature must change from high temperature to low temperature, from order to disorder. There is no way to change this. Just like our mobile phone, when we first bought it, the mobile phone was very smooth, but after using it for a period of time, the mobile phone will become very slow. The longer it is, the more stuck the phone will become. Everything is the same, and Clausius believes that this phenomenon is irreversible, because the entire universe is increasing in entropy, and entropy increase is also the highest law in the universe. From a macro perspective, entropy is constantly increasing, which is the ultimate law of the evolution of all things. This also means that no matter how hard humans try, it is impossible to change this law.
In addition, time travel also violates the law of conservation of energy. According to the law of conservation of energy, we can know that energy can only be transformed and transferred. In fact, matter itself is a manifestation of energy. If time travel really happens, it violates the law of conservation of energy, so time travel is impossible. In order to prove that time travel cannot be realized, the famous matter The physicist Hawking also conducted an experiment in 2009. At that time, he held a party and invited time travelers from the future. However, Hawking did not tell anyone at the time and only sent out invitations after the party. If time travel is real, then there should be people in the future who are willing to come to this party. But in fact, no one came to this party at all. To a certain extent, time travel is impossible to achieve.
And Hawking believed in an interview that from the perspective of general relativity , time travel can indeed be carried out by distorting time and space, but distorting time and space will produce huge radiation and destroy the spacecraft in an instant, so Hawking believes that time travel is impossible to achieve, and in Einstein It is mentioned in the theory of relativity that any object with mass cannot reach the speed of light, let alone exceed the speed of light. For example, if we are on a train with 90% of the speed of light and then move forward at 20% of the speed of light, then our speed should be 110% of the speed of light. However, in the world of light speed, the superposition of speeds is different from what we think of. No matter how we superimpose, it is impossible to exceed the speed of light.
Because when the speed of an object reaches the speed of light, its mass will become infinite. In our current physics, there is no infinite matter at all, so the speed of the object cannot exceed the speed of light, and everything in the universe follows the law of causality , because all events will produce certain results after they are born. For example, a person is born in time. The death of a person also occurs at a certain time and space coordinate. The most obvious difference between these two coordinates is that they occur at different times. In fact, the time coordinate of death must be after the time coordinate of birth, that is, the occurrence time of the last event must be later than the time of the first event. The time coordinate of the last event, minus the time coordinate of the first event, must be greater than 0.
If super-light speed exists, then when humans move at super-light speed, the time coordinates will go backward instead of forward. This process will cause the final subtraction of time coordinates to be negative, and time can only go forward but not backward, so time travel is impossible. In fact, it is a problem for many people that time travel is impossible. This kind of regret, if time travel cannot be realized, it means that what happened in the past can never be changed. Regrets will eventually turn into regrets. There is never a way to make up for things missed. These things will always stay in the past time. For now, this theory will not change unless we can enter the four-dimensional space. The four-dimensional space is based on the three-dimensional space with a time dimension added in our world. Time cannot be quantified and we cannot change the passage of time.
But in four-dimensional space, time can be quantified, and we can change the changes of time at will. The space we live in is a three-dimensional space composed of length, width, and height. Adding a time dimension to the three-dimensional space becomes a four-dimensional space. The four-dimensional space is more like a movie that can be controlled. If our life is regarded as a movie, then The four-dimensional space is a movie that can control time. For example, when we watch a movie, we can fast forward and rewind time, so that we can watch it repeatedly. If we can enter the four-dimensional space, then we can change the timeline. If we want to adjust the timeline to a certain moment, we only need to move our fingers. Therefore, in the four-dimensional space, time travel should be possible. In fact, in the four-dimensional space, time can be changed at any time.
However, it is not easy to enter four-dimensional space. After all, four-dimensional space and three-dimensional space belong to two different dimensional spaces. Just like we cannot enter two-dimensional space, scientists believe that high-dimensional space can observe low-dimensional space, but low-dimensional space cannot see high-dimensional space. Each different dimensional space has its own laws. Three-dimensional space If a creature enters the four-dimensional space, it is difficult for us to imagine what will happen. Moreover, the current four-dimensional space is only a speculation among scientists. Scientists have not confirmed the existence of the four-dimensional space. However, the editor believes that humans are the most intelligent life on earth. Human technology is constantly progressing and developing. With the advancement of human technology in the future, maybe we can find the four-dimensional space and realize time travel. In this regard, do you think time travel can be realized in the future?
