If we can travel through our own life, the passage of time will always be as expected in the past few years. We hope that we can grow up quickly (so as to become more mature), instead of turning back the time, becoming more childish and wanting to live forever. If someone obviously has this ability, but he is anxious to die, it can only be out of his personal religious ideas (here does not mean cults).

? We abandon the theoretical impossibility and boldly assume that if we have a chance to live forever, if time should not be arrogant, if we are as free as a fish in the water in the long river of history, if we can break the barrier of time at will. That would be great. The concept of "time travel" is a frequent visitor to literary and film works. In addition, as a time machine (the full name of DeLorean DMC 12 is a car transformed into a time machine by a crazy scientist in the sci-fi movie Back to the Future, and the appearance of DeLorean has a strong sense of the future, but the power is surprising), it caused trouble at random when traveling in time and space, or it was a "slingshot model" in ancient Japan. All these fantasies can't be proved. But in the mainstream concept, the flow of time is impossible, and science has given it theoretical and data support. In fact, some people have changed their relative time through high-speed movement. These people are not the black technology of NASA LED, but astronauts. Time travel is not complicated. For example, a GPS navigation satellite in orbit can slow down by 38 microseconds every day. "Twin Paradox" is a favorite concept used by scientists to explain time travel. If you sail in the universe for a year at nearly the speed of light (99.995% of the speed of light) and then return to Earth at the same speed, it will be 2 years for you. However, there is a fallacy "Twin Paradox" in the twin paradox. You don't need a brother or other sister. If you spend two years doing this experiment, you can't go back to two years ago. In addition, you can also use wormholes to travel through time and space, but you must return to the spaceship in some way.

So far, the hole that came up with a sudden idea has not been proved to exist, so this method also has its shortcomings. The theory put forward by physicist Frank Tipler on the basis of Cornell lanczos and Willem Jacob van Stockham's previous work is also an unprovable proposition. This proposition is not a fantasy. It holds that after rubbing a very long but dense cylinder with 1 times the mass of the sun, and rotating the long cylinder at a speed of billions of times per minute, the nearby spacecraft will move around the cylinder along a very accurate spiral.

At the same time, Stephen Hawking, an outstanding figure in modern history, also made suggestions for crossing into the future, but this suggestion was as futile as Tippler's column. He devoted more time than the twin paradox, but got little. Different from Tippler's cylinder theory flying around a huge cylinder, the content of this theory is that the spacecraft will fly around a black hole for five years at the speed of light. When the spacecraft stops, people will find that ten years have passed, but why five years become ten years instead of two years and one week becomes two weeks is still unclear. A possible faster way is to stand on a neutron star and use its energy to cross.

however, the result is that you are more likely to die, and where it will take us is unknown. These methods are extremely boring and impractical, and none of them provide a way to return, so these methods are not allowed to be used for time travel. Ironically, though these old sayings are still in our ears, science is still making efforts to develop breakthroughs in these areas. While science looks forward, philosophy seems to pay more attention to the impact of reverse travel.

The first thing to accept when crossing back is that you are most likely to be in a parallel universe formed by your arrival. On the one hand, this concept is a general and generally accepted branch of the concept of time travel; On the other hand, this is the background concept of many popular time travel theories. Take grandfather's paradox as an example: when you commit suicide intentionally or unconsciously or prevent yourself from being born, you should be eliminated in this parallel world. And if so, then you were not born, how can you exist in the world? And if you die, aren't you still alive? A similar problem is the paradox of Hitler's murder. When you plan to go back to the past to kill Hitler or any other famous person, from St. John to Richard Karn, logically, this plan should not be completed.

what remarkable characteristics do people who have been erased from history need to be discovered by you in the future? However, this paradox does raise a question: Can you kill someone you have never heard of before? Back to the grandfather paradox, no, of course not! If you can go back far enough, any ancient person who can breed offspring may be your ancestor. However, we assume that everything can happen in a certain period of time, so a series of brand-new problems will appear in this period of time. Suppose you can kill the biggest rabbit in history or save something better, will history be better in the long run?

or some people or things will never appear again, and let the historical process keep more or less the same direction and get rid of the restrictions of parallel universes. Undoubtedly, traveling to the past will bring two philosophical speculations: either everything you do will bring about changes, because you shouldn't have been here in the first place; Either everything you do is reasonable, because obviously you should complete a round trip here. Whether forward or backward, there will be a closed loop of time. Your crossing takes place on two nodes of history and will appear permanently.

This is a more concrete idea in science fiction than in real science, but physicists in the real world have already evaluated related concepts, such as causal cycle and self-attesting prophecy. Suppose you have erased yourself from history, the farther you go, the less likely you are to experience your future, or the less influence you have on your future. You can't meet yourself, because you are in a universe where you don't exist. But that doesn't mean you can't travel around and get some insight, knowledge and advanced technology. When you are there, it means that the future you witnessed may no longer exist. Once you go back to your own time, suppose what you have done will end, but in any case, if you can travel in time and travel back, what will you do?