Is time travel really possible?

In fact, as long as you understand quantum theory, will you try to combine it with the theory of relativity?

When matter reaches the speed of light, it has already become a quantum (simply put, it is an energy packet). Quantum, that is, energy cannot be transferred to another quantum.

In other words, assuming that one of them is stationary, then classical mechanics allows velocity superposition, but why does relativity not allow it? It is because the speed superposition rate of matter with zero speed (assumed to exist, but does not actually exist) is 100%. However, quantum theory does not allow the speed to be zero, and relativity theory does not allow the speed to be greater than the speed of light, because if it is greater than the speed of light, then the speed will be superimposed. The rate is 0%.

Because speed is relative, once the superposition rate is zero, can you say that this object has speed?

"Science World": Everyone talks about time travel

The article "When will the time machine set off" in the 9th issue of this magazine left three questions, and readers showed great enthusiasm for these questions. Great interest and actively participate in discussions: travel to parallel universes and set up a time travel agency; use the energy of lightning, or become an electromagnetic ghost. They believe that this can solve the paradox that may arise from traveling back and forth between the past and the future. While waiting for the machine designed by scientist Paul Davis to take us to the future, let us take a look at the whimsical ideas of readers!

About the first question: Flying to become younger< /p>

Using the formula mentioned, it can be concluded that 15×10-14 seconds can be earned in every second. Time is indeed very short! If a person traveled non-stop by plane for an entire year, time would slow down by about 5 microseconds.

Many readers have figured this out. It is conceivable that under normal circumstances, traveling every day at the fastest speed we can achieve, we will not get much younger in our lifetime.

About the second question: Back to the Future

For travel in the past time, Paul Davis’s answer is based on wormholes, which most readers think The idea is very novel. However, it is impossible to use a wormhole to travel to a time before it was created. If we built a wormhole today with a time span of 100 years between the two ends, someone could travel back to 2003 a century later.

Technical Issues

Many readers agree with the idea that travel to the future is possible, but only due to some technical details. Some readers said: "It is impossible for 'future people' to break in, because it is impossible for a time machine to go back to the era before it came out." Others think: "People who travel to the past cannot go back to the future, because no matter what In the past or now, people have not been able to travel in time, so travelers cannot go back to their time.”

Some readers clearly stated, “We don’t have time machines now, so will the travelers of the future.” Without such a stop, they cannot visit us."

Some people think that there is a possibility that we are visited by time travelers, "but we will only know when we travel in time in the future."

Some people think that this problem is even more profound: "Using the time machine conceived by Davis, we can only reach a point where the past information has not yet reached, not the source of the information! Therefore, there is no way for future generations to reach it. It is impossible to interact with the information source, and we will not encounter 'him' in the past."

Some people believe that only future travel without turning back is possible, so "we can encounter two types of time. Travelers: Earthly Time Travelers and Extraterrestrial Time Travelers, but Only Travelers from the Past ” If we didn’t meet the first group of travelers due to technical issues, then maybe for the second group. Another question will arise: "Since they built the time machine to go to the future, there may be a gap with our civilization, and their level of civilization is much higher, so this effort is not worth it."

What to do if the "gasoline" runs out

One of the questions Davis raised about future travel is energy. Some readers think this is an insurmountable obstacle, "With a little calculation, I know that if hydrogen is used as the propellant of the spacecraft, the amount used is almost 1 cubic kilometer."

However, some people are interested in reducing costs. The possibilities are more optimistic: "Why not harness the energy of lightning or hurricanes?"

We don't know what Paul Davis was thinking, but we should ask what container would be used to hold them energy!

Is it crazy or...

"I wonder if someone will be sent to a mental hospital because they say they are from the future, and my doubt is that even if there is time from the future Traveler, will he tell the truth? "Someone said in the letter, "If someone knocks on our door one day and says that he is our descendant, who among us will believe it?"

< p>Other people have the same view: "Maybe we already have future travelers, but we haven't discovered them. So how can we tell the difference? Even if he says he comes from the future, who will believe it?"< /p>

Some people think further: "We imagine that we are time travelers and we come to 1930.

If we spoke to people like this, they would think us crazy and put us in a lunatic asylum! ”

Let’s go crazy together

Some readers are more imaginative: We might as well imagine that in the distant future, time travel has become commonplace. By then, a world-class The travel agency arranged everything for us.

“The travel agency is divided into two specific groups. Some people are in charge of administration, public relations and planning, while another group is responsible for accompanying scientists and other tourist groups to prevent future residents from coming into contact with their past relatives or others. "

Someone thought of legal issues: "There must be a principle of non-interference to prevent time travelers from being recognized. ”

Someone reminded people to be cautious: “Time travelers should take precautions and not be completely confused with the time they are going to.” For example, if a time traveler decides to go to the Middle Ages, he must prepare a suit of knight's armor, learn some chivalry, and be very talkative. ”

Some readers naively believe that there should be some rules to prevent reckless time travelers from interfering with the era they are visiting. “I think measures should be taken to prevent possible interference and avoid passing through shorter Travel to meet other people. Perhaps the scientific community of the past simply needs to be persuaded to try to avoid direct contact between travelers and their ancestors. ”

Pessimists

What if time travel is impossible? Not because of technical problems, but because the past was in a universe parallel to ours. Some people are convinced of this , believes, “If someone wants to travel through time, the huge magnetic field deformation will cause him to lose his memory. "Some readers think that time travel is impossible. If the paradox is admitted, it means that there is no real universe, and there is no scientific and rational order. Some people think that it is not that complicated, "everything in the universe" Everything in a moment exists in the absolute present tense. No time travel whatsoever! "

Parallel Universes

The idea of ??parallel universes proposed by Stephen Hawking has attracted many readers. Some readers believe that "travelers from the future can only enter the past of a parallel universe. Or now, it will not affect our present." Some readers have more interesting ideas: "Once we meet our own descendants, natural forces will throw us into a parallel universe, leaving our 'copies' with the travelers '. ”

Some people think this: “Anyone who travels to the past will interfere with history and end up entering a parallel universe instead of ours.” "

Some people have proposed an answer, believing that the time traveler "will undergo a molecular-level transformation, turning it into an electromagnetic ghost, unable to affect the physical body or anything else. ”

Although some people do not believe in the possibility of time travel, they are deeply attracted by this theory: “Our universe may be one of countless possible variants in the endless universe. Each one has its own history and life. "

Like a movie

The past is portrayed as indelible and therefore cannot be changed. This is the view of some: "Why should we change the status quo and correct the mistakes of the past Woolen cloth? We are just traveling. "If we use film to record a person's life one by one, then this film is the person's past and cannot be changed, because it is recorded.

Some people also use Film explains the impossibility of interacting with the past when traveling backwards in time: “We can see the film moving backwards, but we cannot enter the film (where we traveled during the trip). ”

About the third question: Whose credit

The teacher-student paradox that David Deutsch came up with is the most troublesome. No There is no internal contradiction, and I don’t know where this news comes from. Deutsch himself believes that it hits the key to the orderly rationality of nature, which is comparable to the idea of ????perpetual motion.

Some people think that the credit lies with the professor

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Some readers thought: “Judging from the series of things the professor has experienced, we tend to attribute it to the professor. But this may not be a matter of discovery rights. For a theory, the specific way it is proposed does not matter at all. What matters is that it was proposed. ”

Some readers said wittily, “Discovery has no source, it just exists and becomes an integral part of the universe.” ”

Others believe that the right of discovery should belong to the professor: “Without his discoveries, students would have nothing to publish.” It can be said that it was his help to the students that enabled her to later develop and publish this solution. "

Some people also support the students

Some people believe that this discovery belongs to the female students in the first process of the development of the incident. "After the professor's time travel, due to the change of cognitive process, , so we can no longer view him as the same person. "Someone said, "If she had not had such an idea in her brain, the professor would never have found the information describing these solutions. ”

In the eyes of some people, there is no doubt about this, because “the only purpose of returning to the past is to teach the solution to his students, which will lead to another past for the professor.” Both There is no impact on each other.

Multidimensional travel

However, the readers' creative thinking goes beyond this.

Some people also raised new questions.

For example, some people doubted "whether there is actual time" and made a philosophical conclusion: "Sometimes reality far exceeds illusion. The latest physical research shows that we live in a world with 11 or even more dimensions. So why do we Want to talk about time travel instead of dimensional travel? And in all dimensions! ”

What an interesting idea! Everything has to wait for the experts to build a time machine.

Three questions

1. According to the theory of relativity, any movement is time travel. The faster the speed, the more obvious the effect of time travel. So, all of us today can time travel if we want to. A flight on a regular airliner is a brief moment of time travel.

In fact, time passes slower for people flying in the sky than for people sitting at home. Although this difference is not noticeable, it can be measured. It increases as the speed increases. increase.

How much younger would a person be if he traveled by plane with an average speed of 600 kilometers per hour?

The following formula can be used to calculate the specific value of time slowing down during motion:

Where V is the actual speed of the moving object, and C is the speed of light.

2. Compared to traveling by plane, when it comes to time travel, what people think of is taking a giant leap in time in the past or future. If we are indeed building a machine that allows people to travel in time, why has no one ever encountered a descendant of themselves traveling in time into the future? This is a question asked by Stephen Hawking. Do you know how to answer him?

3. Time flies by 50 years, and time travel has become a common thing for people. A mathematics professor in 2050 was driven by curiosity to travel to 2060. In the library of his school, he discovered an amazing solution to Einstein's equation. This solution was published in "Science World". The author is a young female student.

The professor, who was excited about this discovery, went back to 2050 to look for the female student, and found her among the first-year students. The professor described the solution to the equation to her.

The female student learned this solution and published it in "Science World".

What is the real source of the professor's discovery?

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“The theory of relativity provides us with There are two ways to travel in the future. One is to move at high speed, and the time distortion caused by this movement is explained by the special theory of relativity. If we have a spacecraft with a speed of 99.99999% of the speed of light. It is possible to enter the year 3000 AD in 6 months. "This kind of travel is a result of the theory of relativity, which is related to the famous "twin paradox" and is a direct result of Einstein's theory. The older twin begins his journey into space at nearly the speed of light, while the younger brother remains at home. After my brother reached his destination 10 light-years away, he immediately returned at the same speed.

For the younger brother who stayed on the earth, time passed by for 20 years, which was the time it took for the older brother to travel at nearly the speed of light. But for the traveling brother, time passes much more slowly. In fact, the theory of relativity tells us that time slows down as speed increases. For my brother, only three years have passed. When he returns to Earth, he will find that he has stepped into the future 17 years later.

According to these theories, people can travel very close to the speed of light, but can they actually reach such high speeds?

There are no off limits in this regard, it is just a matter of cost. In order to accelerate a 10-ton load to 99.9% of the speed of light, 10 billion quintillion joules are needed, which is equivalent to the total energy production of all mankind in several months. ”

The cost of getting closer to 300,000 kilometers per second will of course be higher.

So, as long as we have the necessary capital, we can start towards the future?

"I don't rule out that we can do this, there are inexhaustible sources of energy in space, if only we develop them. It actually became a political issue: making decisions about the necessary technological research and development into space to enable humanity to harness the vast amounts of energy in the universe. But there's another problem: time travel using a high-speed system might only allow you to go into the future but not come back. In fact, if our super spaceship reaches 3000 AD and then returns, it may only take another big step in the future of the earth. ”

This is because time travel does not depend on the direction of movement, but only on its speed.

The possibility of traveling in the past raises some real questions. A fascinating, seemingly irresolvable paradox at its simplest: a time traveler goes back in time and kills the biological mother of a girl who was then unable to do so. Birth would not be able to complete the murder. These contradictions make the concept of causality into a dilemma, and science based on causal logical relationships is also difficult to stand on.

Stephen Hawking put an end to this problem with his "chronological preservation hypothesis": Nature will always find a way to prevent people from traveling into the past.

Paul Davis believes that subsequent events can affect previous events, but only if there are some closed timelines between events that have no causal relationship. For example, a rich man’s wealth came from the benefactor who helped his great-grandmother a century ago. He took a time ship to the past to find this kind person. After meeting his great-grandmother, he explained to him that he was a time The traveler, in order to make the other party believe it, showed his great-grandmother a newspaper he brought from the future. After seeing the stock price in the newspaper, the great-grandmother began to invest in the stock market and thus brought huge wealth to future generations. The wealthy businessman finally understood that he It is the benefactor. This example is not a problem for Davis, but the problem posed by the matricide time traveler cannot be solved. It is impossible for anyone to kill their ancestors.

David Deutsch, an expert on time travel, uses some laws of quantum physics to answer these contradictions. In the subatomic world, quantum uncertainty dominates: an electron hitting a proton can turn to the left or to the right, with no rules. In the view of some physicists, this uncertainty creates a multiplicity of universes, with every time an electron turns to the right it creates a new universe with an electron that turns to the left. According to Deutsch, the aforementioned contradiction could be resolved in the same way: if a time traveler intervened in history, the universe would branch into two or more branches, and the slain mother would travel to another parallel one. in the universe, and will not enter the universe where the matricide belongs.

I think time travel is impossible