】 【Definition of time travel Is a science fiction time travel activity of a person to leave now while the exposure to future or past. In science fiction, time travel is one of the most exciting idea. Board the time machine, a person can use a control system for the determination of any date (past or future), then Time Machine can in an instant and took him to that era, scientists believe that even if this becomes a reality, it will serve as a tourist not change history. In the time machine, a person's age into the machine together with the same age at the time. Scientists believe that time travel can not become a reality, after all, we have not seen the traveling time machine from the future visitors. Under the existing scientific system, the time has a strict one-way. In all of the physical laws, only the second law of thermodynamics with the direction of the arrow of time, which gives people a sense of time is no longer flowing passage. So back to review the past, or early visual impact to the future, become an eternal human dream. 】 【Relativistic 】 【Possibility of time travel The possibility of time travel in the field of theoretical physics has been discussed very seriously was. h • g • Wells in "Time Machine" explored the possibilities are as numerous other science fiction writers do. Many science fiction concepts such as submarines and flying to the moon, etc., achieved by science. So, time travel prospects? • Kurt Godel in 1949 discovered a new theory of general relativity allows time and space. This is the first time that the laws of physics do allow people to travel in time. Gödel was a mathematician, he was proved the incompleteness theorems and reputed the world. This theorem is to say, impossible to prove all true statements, even if you limit yourself to prove that such a glance as the arithmetic and all the really boring subject statement. This theorem is perhaps our ability to understand and predict the fundamental limits of the universe, but so far it has not become an obstacle for a complete unified theory. Gödel and Einstein at Princeton in advanced academic research spend their old age, familiar with the general theory of relativity. He has a strange nature of time and space: The entire universe is rotating. One might ask: "What things that rotate relative to?" The answer is that distant objects around the small gyro or gyros to point rotation. This leads to an additional effect, one astronaut before his departure that can be returned to Earth. This property is very frustrating to Albert Einstein, who had thought that general relativity does not allow time travel. However, in view of Einstein's theory of gravitational collapse and uncertainty groundless objections, which may actually be an encouraging sign. Because we can prove that the universe in which we live is not rotating, Gödel does not correspond to the solution found it. It also has a non-zero cosmological constant. Einstein's cosmological constant is that the universe is the same as when introduced. Hubble discovered the expansion of the universe, the cosmological constant is no longer needed, and now generally agreed that it should be zero. However, after the other from the general theory of relativity has found a more reasonable time and space, they allow travel to the past. One of them is inside the black hole rotation. Another is included two fast time and space through the cosmic strings. As the name implies, cosmic strings are string-like objects, it has length, but the section is very small. In fact, they are more like a giant rubber band under tension, the tension is about 100 million million million tons. To a cosmic string tied to the earth, the earth will be time in the 1/3o seconds from zero miles per hour (1 mile = 1.609 km) to accelerate to 60 miles per hour. It sounds like the beginning of cosmic string material science fiction, there is reason to believe that it can be in the early universe produce symmetry breaking mechanism. Because cosmic strings with great tension, and can start from any form, so once they are spread out, it will accelerate to a very high speed. Gödel's solution and the cosmic string space-time distortions in the beginning, so always travel to the past. God may be a creation of the universe is so curly, but we have no reason to believe that his God will do so. Microwave background and the light element abundance observations indicate that the early universe and the curvature does not allow time travel. If the no-boundary proposal is correct, based on the theory can also be exported to this conclusion. So the question becomes: if the universe did not have time to travel the initial curvature necessary, we can then curl the space of the local area to such a degree that allows time travel? Quick interstellar or intergalactic travel is a closely related issue, but also of interest to science fiction writers. According to relativity, nothing move faster than light. Therefore, if we the nearest star to our α-Centauri - Send space ship, as it is about 4 light years away, so we expect at least 8 years to wait until the travelers to come back to report their findings. If you go explore the galaxy center, at least 10 years before returning. Relativity does give us some relief. A young lady were White, She can do it faster went fairly light. Her relative way, Just starting on the day, Already arrived in the night before. The key is that there is no theory of relativity all observers agree that the only time measurement. On the contrary, each have their own time measurement observer. If a rocket at less than the speed of light from the event a (such as the 2012 Olympic 100 meters final race) to the event b (such as α-Centauri Parliament's opening session, 100,004), then based on all observations by the time they all agreed the event a place in the event b of the first. However, assuming that the spacecraft must be more than the speed of light sent a message to the Competition Council, then the observers at different velocities on what the event a and event b after the former what is controversial. According to one observer at rest relative to Earth, perhaps the opening of Parliament after the contest. In this way, the observer would think that if he ignores the speed of light restriction, the spacecraft arrived in time from a b. However, in the α-Centaur seat close to the speed of light flying in the direction of the observer to leave the Earth will feel the event b, that is, the opening of Parliament, first in the event a, that is, place the final meters. Theory of relativity tells us. For observers at different velocities, the laws of physics are the same. This experiment has been well tested. It is believed that the use of more advanced theory to replace relativity, it will still be retained as a characteristics. Thus, if FTL travel is possible, movement of observers would say that it is possible from the event b, that is, the opening ceremony of Parliament, rushed to the events a, that is, meters race. If he is moving so quickly, he even had time before the event back, and in that case who is the winner put down stakes. There are some barriers to break the speed of light problem. Theory of relativity tells us that the speed of the spacecraft closer to the speed of light for its power to accelerate the rocket to be growing. We have experimental evidence for this, but not the space shuttle experience, but such as Fermilab or CERN particle accelerator in the experience of elementary particles. We can accelerate particles to 99.99% the speed of light, but no matter how much we are into power, nor can they accelerate beyond the speed of light barriers. Space shuttle situation was similar: no matter how high power rocket, and can not accelerate to the speed of light above. 】 【Wormhole Wormhole, also known as worm holes. It would appear that rapid space of time travel and travel seems to have the feasible. However, there may be ways. Perhaps people can curl up into space, making a and b between a short cut. Between the a and b is a sure way to create a wormhole. As the name suggests, is a space-time wormhole thin tube, which can both nearly flat regions far apart connected. Wormhole-based time machine built three simple steps is not 1. To find or create a wormhole to open up a tunnel used to connect two different regions in space. Large wormholes might naturally in outer space, is the remnants of the Big Bang. If not true, then we had to make do with smaller than atoms wormhole, either natural products (around us, every moment has a small wormhole that birth and death), or man-made products ( shown on such place, they are produced by a particle accelerator). These smaller wormhole must be extended to a practical size, may have to use those in the lead shortly after the Big Bang space expansion of the energy field. 2. The wormhole stabilized. The casimir effect into the so-called negative energy generated by the quantum, the wormhole would allow the signals and objects safely across it. Negative energy density will resist for the wormhole collapse or near-infinite infinite point of the trend. In other words, it prevents the wormhole turned into a black hole. 3. Traction wormhole. A highly advanced technology spacecraft will separate from each other wormhole entrance. An entry may be placed in the neutron star surface, it is a strong gravitational field, extremely dense stars. Strong gravity makes time slow down. Another entrance to the wormhole as time goes by faster, the results of these two entrances, not only in space but in time have been divided leave. The leap to high-speed movement is a way of the future. Gravity is another means. In einstein's general relativity, he predicted that gravity can slow the passage of time. Compared with in the basement, bell to go faster on some of the top floor, in the center of the earth and thus closer to more in-depth in the case of gravitational field, this phenomenon will become more significant. Similarly, the clock in space go faster than the ground. Although this effect is minimal, but it has been directly measured precise clock. Indeed, global positioning system must take into account the time bending effects. If they do not take this into account, sailors, taxi drivers and cruise missiles will find their own provisions deviate from the track there are many kilometers. Until now, I have discussed the future of travel in the time North Korea situation. So retrograde what will happen? This will happen far into the issue. In 1948, Princeton, New Jersey Institute for Advanced Studies kurt gabriel Einstein gravitational field equation is proposed as a solution describes rotation of the universe. In this universe, an astronaut to travel in space to achieve the purpose of back. This is the result of gravitational influence of light. Lead to optical rotation of the universe (and therefore also the causal link between things) was grabbed and surrounded in its interior, which makes a kind in a closed loop can be closed in the space to move, but also in the closed loop in time travel, but not at any time over the speed of light relative to the adjacent particles. gabriel's explanation is as mathematical adventures and shelved - after all, there is no evidence that the universe as a whole observed in the rotation. But his results show retrograde in time does not violate relativity. Indeed, Einstein said he worked his theory may in some cases allowed to return to the idea of the past confused. Allowed to return to the past a number of other suspect has been found. For example, in 1974, tulane university frank j. tipler calculate a huge rotating infinitely long cylinder, its axis in place, astronauts were able to visit close to the speed of light to their own past, that is, near the cylinder drag drag a ring of light. In 1991, Princeton University, j. richard gott predicted cosmic strings - cosmologists imagine its structure is produced in the early Big Bang - and can produce similar results. But the 20th century, the emergence of the mid-80s time machine the most realistic scenario is based on the concept of wormhole conceived. In science fiction, wormholes are sometimes called Star Gate; they provide a through space far away from each other, a shortcut between two points. Skip a hypothetical wormhole, you may appear in a moment later the other side of the galaxy. Wormhole naturally found general relativity, with gravity, not only can bend space, but also allow time distorted. Theory allows to connect two points in the optional space in the tunnel path and the existence of such a thing. Mathematicians proposed space in the form of multiple links. As the end of the tunnel through the mountain road surface than the shorter mountain, like a wormhole may also throughout the general space than the usual route to more short. Carl Sagan in his 1985 novel "Contact", in relation to use of the wormhole as a fictional device. In Sagan's suggestion, kip s. thorne and his colleagues at the California Institute of Technology _set_ out to study the physics of the wormhole is consistent with the known. Their starting point is the same wormhole as a black hole with terrible gravity of the object. But the difference is the black hole, which is not only a one-way travel destinations, and the wormhole will also have an outlet and an entrance. Is available through the wormhole, it must contain strange matter thorne said. In fact, this is some kind of anti-gravity effect can produce a large-scale system to resist the powerful gravity of its own that was pressed into the natural tendency of the material the black hole. Anti-gravity, or other than the repulsion from the negative to produce energy or negative pressure. As we all know, the negative energy state exists in a particular quantum system, it does not matter that the singular thorne was prohibited by the laws of physics, although it is not clear whether collected enough material against gravity in order to stabilize a wormhole. Soon thorne and his colleagues realized that if a stable wormhole can be created, it can easily turn into a time machine. Perhaps one of the astronauts through the wormhole can not only occur somewhere in the universe, but also in a certain period, that is - in the future or the past. To make a wormhole for time travel, it is a hole which leads to a neutron star should be there, and placed close to the neutron star surface areas. Stellar gravity will slow the passage of time near the wormhole openings, which makes the time difference between the two ends of the wormhole gradually accumulated. If two ports are placed in the right place in space, then the time difference will remain frozen. Assuming that this difference is 10 years. An astronaut from one direction through the wormhole, he will jump to 10 years in the future, on the contrary, if the astronauts through the wormhole from another direction, he will jump past 10 years. The second astronaut in space at high speed through the usual back to the starting point, he might be coming home before departure. In other words, the closed loop space might turn into a time in the ring. One limitation is the first time, astronauts can not go back to the period before the establishment of a wormhole. A terrible challenge is the initial creation of the wormhole would hamper the manufacture of a wormhole-based time machine. Perhaps such a class structure of space from the string of natural fused - remnants of the Big Bang. If this is the case, a super-civilization would be able to use a wormhole. Perhaps the wormhole is in a very small scale (the so-called Planck length, about 10-20 nuclear scale is so small) naturally occurring. In principle, such a tiny pulse of energy may be to stabilize the wormhole, and then expanded in some way to can take advantage of size. If the many engineering challenges have been overcome, time machine production will open Pandora's Box causal paradox. For example, a time traveler to visit the past, the murder of a young girl's mother. How do we understand these things mean? If this girl died, she can not be time traveler's mother. But if it were time travelers never had, he would not return to the past and the murder of his mother. The mother of the famous paradox (sometimes with other family relationship to systematic exposition) is due to people or objects can reverse time and change the past caused. Pinball is a simplified version of the case. A marble through a wormhole-based time machine, then it will hit at the time of its own earlier, thereby preventing it from ever entering the wormhole. Paradox solutions from a simple understanding: marbles can not go against logic or act in violation of the laws of physics. It certainly can not stop going through the wormhole in their own way, but nothing will stop an infinite number of marbles in other ways through the wormhole. Quantum Physics】 【 Space-time wormhole between different regions is not science fiction writers thought the invention, its origin is very respectable. Energy a bit like money: if you have positive energy, you can use different methods of distribution, but based on the classic beginning of this century that law, you do not allow overdrafts. Thus, these classical laws exclude any possibility of time travel. However, quantum laws have gone beyond the classical law. Uncertainty principle of quantum laws are based. Some of the quantum laws of more generous, as long as you total energy is positive, you will allow from one or two accounts overdrawn. In other words, quantum theory allows the energy density in some places is negative, as long as it is in other places by the energy density of the compensation, so the total energy remains positive. Quantum theory allows negative energy density is an example of the so-called Casimir effect, and we even considered "empty" space is filled with virtual particles and virtual anti-particles, which appear together in minutes and then back together and annihilate each other. Now, assume that people have two very close parallel metal plates. Metal mirrors for the virtual photon plays a similar role. In fact, in a cavity formed between them. It is a bit like organ pipes, only specify the scale of the resonance. This means that only when the plate is the distance between the virtual photon wavelength (the distance between adjacent peaks) of an integer multiple of, these virtual photons into space will appear in the flat. If the cavity width is a multiple of the wavelength of the fact that some wavelengths, then reflected many times before and after the crest of a wave trough will coincide with another, this was off_set_ fluctuations. Because the plate can have a virtual photon between the resonant wavelength, so the number of virtual photons outside the region than in the flat slightly less, than in the flat virtual photon can have any wavelength. So people can expect to suffer the two pieces flat force them to squeeze inside. This force actually measured. And and the predicted values. In this way, we get the existence of virtual particles and has the effect of the experimental evidence is. In the flat there are fewer virtual photons between the fact that the energy density means that they are much smaller than it is at. But away from the flat of the "empty" space, the total energy density must be zero, because otherwise, the energy density of space would curl up, but can not remain nearly flat. Thus, if the plate than the distance between the energy density of the energy density is smaller, it must be negative. However, the alien or any person from the future visits should be more obvious, perhaps even more unpleasant. If they are apparitions, why only those who are considered less reliable witnesses? If they try to warn us of imminent disaster, this is not very effective. A kind of visitor from the future possible explanation is the absence, as we observed in the past and found that it was not allowed to travel back from the future, the kind needed to curl, so the past is fixed. On the other hand, the future is unknown open, so it may be necessary curvature. This means that any time travel had been limited to the future. At this moment, Captain Kirk and the interstellar ship not have a chance. 】 【Contradiction This may explain why the world is not full of tourists from the future. But if people can go back and change history, the problem can not be avoided. For example, suppose you go back to the past and your ancestors killed when he was still a child. There are many versions of these paradoxes, but they basically are equivalent: if a person is free to change the past, he will encounter conflict. It seems there are two ways to solve the paradox caused by time travel. Historical method, called coordination. It is about, even when space is curled too may travel to the past, what happened in space and time must be the solution of the coordination of the laws of physics. According to this view, unless the history suggests that you have arrived in the past, and did not kill your ancestors or any act not in conflict with your current situation, you can return to the past. Moreover, when you return to the past, you can not change the historical record. That means that you are not free will do whatever they want. Of course, one could say that free will is illusory anyway. Constraints if there is indeed a complete unified theory of all things, it should determine your actions. But for such a complex organism like humans, their constraints and decisions can not be calculated way. We say that people have the will, is that we can not predict their future actions. However, if a person off of travel by rocket and spacecraft have returned before this, we will be able to predict their future behavior, because that would be part of recorded history. Thus, in this case, the time traveler time travel is not free will to solve the other possible scenario is known as the choice of history. The idea is that when the time travelers back to the past, he entered the historical record and the history of different to the other. In this way, they are free to act and not consistent with the history of the original constraints. Stephen Parker • Spiro very favorite movie, "Return to the Future" idea: Mati • Mark Frye and his parents to return to historical change more satisfying love. Feynman sum over histories allows the micro-scale travel to the past. Scientific laws in the United cpt symmetry unchanged. This suggests that an anti-clockwise spin and b from a movement to the anti-particles can also be considered to be in the direction of the spin the clock back to a movement from the usual b particles. Similarly, a forward movement in time is equivalent to the usual particle movement in the next time the anti-particles. "Empty" space is filled with virtual particles and anti-particles, they appear together, separation, and then return to a mutual annihilation. That way, people can put on the particle that is in space and time along a closed movement of individual particles in Fig. When the pair in the forward movement in time (starting from the event it appears to reach its annihilation of the event), it is called Particles. However, when the particle movement back in time (starting from the arrival of the annihilation of the incident it appears the incident), anti-particles can be said to forward movement in time. In explaining why black holes emit particles and radiation that the virtual particle / anti-particle of a member (such as anti-particles) will fall into the black hole to the other members of the stay, lose and its annihilation partner. The particles can also be discarded into the black hole, but it can also break free from a nearby black hole. If so, for a distant observer, it as a particles emitted from black holes appear. However, it is the mechanism for black hole radiation is equivalent to different images. People can put that into the virtual black hole of the members (such as anti-particles) as the time from the black hole in the back out of the particle motion. When it reaches the virtual particle-antiparticle pair appeared together with the point, it is scattered into the gravitational field to escape from a black hole in the forward movement in time of particles. Conversely, if the members of virtual pair of particles falling into the black hole, one could think it out from the black hole back in time in the movement of anti-particles. This shows that the black hole radiation, quantum theory at the micro scale to allow back in time in the campaign, and this time travel can produce observable effects. The resulting question: quantum theory at the macro scale can be used to allow people time to travel? At first glance should be possible. Feynman's vision of history is the sum of all the history of the. Thus, it should include is curled to allow space travel to the past. Why, then, we have not harassed by history? For example, suppose some people back, and to provide atomic secrets to the Nazis? If the defense called the timing conjecture, these problems will be avoided. It is speaking, the laws of physics prevent the macroscopic objects to pass information to the past. It is the same as the universe supervision guess, is not proven, but the reason to believe that it is established. When the time travelers try to change the past, such was not the paradox appears. But that does not prevent a person to become part of the past. Assume that the time travelers back in time to save from the murder of a young girl, the girl grew up to be his mother. So now is the self-consistent causal link, and no paradox. Causal consistency might impose restrictions on the time traveler can do things, but this does not rule out time travel itself. Time travel bizarre reasoning led some scientists reject the idea completely. Cambridge University's Stephen Hawking proposed a "chronology protection conjecture", which will announce the failure of the causal loop. As we all know, the theory of relativity to allow causal loop exists, a chronology protection is necessary to introduce other factors to mediate, to prevent travel to the past to happen. This factor may be what is it? One proposal is to solve the problem of quantum process. Time Machine will allow the existence of particles circulating into their past. The results suggest a disturbance will occur immediately self-enhancement, resulting from the surge of energy to escape can cause wormhole collapse. Chronology protection is still nothing but a guess, it still retained the possibility of time travel. A final solution to resolve the matter of quantum mechanics and gravity must be looking forward to the successful combination, perhaps with the expansion of string theory or its theory that the so-called m-theory. We even can imagine the next generation of particle accelerators will be able to generate atomic-scale Shakespeare wormhole, they can exist long enough to make the vicinity of the implementation of fleeting particles can cause ring. This time machine to Biweiersi imagination for much more far-reaching, it will forever change our picture of physical reality.
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No. 2
】 【Definition of time travel The concept of time travel first appeared in science fiction, it is one of the most exciting idea, boarded a time machine, a person can use any of the control system determines the date (past or future), and can in the time machine instantly took him to that era. The problem is Time Machine will produce significant paradox, a person can kill him before he was born his father, thus preventing his own birth. Some scientists believe that nature is always smart people outsmart time travel, so that they can form any paradox can not complete the act, that is, you can not kill your father about, or his own. But such explanations are too far-fetched. In fact the concept of time travel itself is vague, it is of great interest to it I'm afraid the time of the past and the future from a strong curiosity. We return to the past to describe a situation, such as you take the time machine back to the past and see yourself, which means you have seen in childhood, an adult self. Otherwise it can not be justified, can not be called back to the past, at best, and the world of the past to see a similar world. Since it is back to not a shred of bias. Equally, you see that you also have to take in the future time machine to go back. The "he" seems to have by your interpretation of the future, and the same future you have a "you", that is, what your childhood met "you" interpretation before. And it seems that everything is OK, and everyone is determined in the interpretation of the history of it. But obviously we can intervene, "history", the time machine to exist means that you will know the results, and you can change this result, this is the paradox. Time and the universe in the simple concept has a unique, that is, if there is a universe outside the universe, people naturally will put these two universes together as a universe. But in pure logic, the universe can indeed have another (even more than the universe), the two are independent of the universe by developing their own rules, time travel is to get to another universe, you might see another universe you. Of course, under this strict interpretation of the same reasoning has many flaws, two buildings linked to the words of one but each other effect is a lot of problems need coordination. In fact time is not directional, time and space are the material we describe the real world into the abstract when it is not as solid particles of matter that objective is to carry out mathematical description of the real world into a time measurement concepts. Time and space in the status of these mathematical formulas are very similar, but slightly different, the time is not static, it always gives us a constantly "passing" feeling. But in fact this is because the world is constantly changing, so we think this is the time "passing" the underlying causes. If you are confused, then the concept of time, rather, time simply does not exist, there's nothing but an evolving universe. The concept of time is described in this Yanhua produced when the universe, but now we really want to own the concept of consciousness to a variation of dominating the universe, would like to see the reversal of time or time of travel. You can use any technical means to ascertain the past and future information, or that construct the reality of the past or future. You can even construct more in theory the universe, producing all kinds of amazing theory, as long as they do not violate the laws of physics, and there are strict mathematical reasoning. But these are not time travel, do not try to jump to the next in time. Time is indeed the speed of the points can be, under the strong gravity will slow down the clock, if a person is not under such a strong gravitational broken down, then he returned to Earth, it will certainly younger than the others. But time will not be back, and space Which can be the opposite direction along the road. In the special theory of relativity, the faster the movement, slower time, so people will say that if more than the speed of light, the time will fall over. But you should find that the movement for more than the speed of light, that transformation has become a virtual number of factors, but it should be considered only negative is the time reversal. Under the existing scientific system, the time has a strict one-way. In all of the physical laws, only the second law of thermodynamics with the direction of the arrow of time, which gives people a sense of time is no longer flowing passage. So back to review the past, or early visual impact to the future, become an eternal human dream. 】 【Relativistic 】 【Possibility of time travel The possibility of time travel in the field of theoretical physics has been discussed very seriously was. H • G • Wells in "Time Machine" explored the possibilities are as numerous other science fiction writers do. Many science fiction concepts such as submarines and flying to the moon, etc., achieved by science. So, time travel prospects? Kurt Godel in 1949 discovered a new theory of general relativity allows time and space. This is the first time that the laws of physics do allow people to travel in time. Gödel was a mathematician, he was proved the incompleteness theorems and reputed the world. This theorem is to say, impossible to prove all true statements, even if you limit yourself to prove that such a glance as the arithmetic and all the really boring subject statement. This theorem is perhaps our ability to understand and predict the fundamental limits of the universe, but so far it has not become an obstacle for a complete unified theory. Gödel and Einstein at Princeton in advanced academic research spend their old age, familiar with the general theory of relativity. He has a strange nature of time and space: The entire universe is rotating. One might ask: "What things that rotate relative to?" The answer is that distant objects around the small gyro or gyros to point rotation. This leads to an additional effect, one astronaut before his departure that can be returned to Earth. This property is very frustrating to Albert Einstein, who had thought that general relativity does not allow time travel. However, in view of Einstein's theory of gravitational collapse and uncertainty groundless objections, which may actually be an encouraging sign. Because we can prove that the universe in which we live is not rotating, Gödel does not correspond to the solution found it. It also has a non-zero cosmological constant. Einstein's cosmological constant is that the universe is the same as when introduced. Hubble discovered the expansion of the universe, the cosmological constant is no longer needed, and now generally agreed that it should be zero. However, after the other from the general theory of relativity has found a more reasonable time and space, they allow travel to the past. One of them is inside the black hole rotation. Another is included two fast time and space through the cosmic strings. As the name implies, cosmic strings are string-like objects, it has length, but the section is very small. In fact, they are more like a giant rubber band under tension, the tension is about 100 million million million tons. To a cosmic string tied to the earth, the earth will be time in the 1/3O seconds from zero miles per hour (1 mile = 1.609 km) to accelerate to 60 miles an hour. It sounds like the beginning of cosmic string material science fiction, there is reason to believe that it can be in the early universe produce symmetry breaking mechanism. Because cosmic strings with great tension, and can start from any form, so once they are spread out, it will accelerate to a very high speed. Gödel's solution and the cosmic string space-time distortions in the beginning, so always travel to the past. God may be a creation of the universe is so curly, but we have no reason to believe that his God will do so. Microwave background and the light element abundance observations indicate that the early universe and the curvature does not allow time travel. If the no-boundary proposal is correct, based on the theory can also be exported to this conclusion. So the question becomes: if the universe did not have time to travel the initial curvature necessary, we can then curl the space of the local area to such a degree that allows time travel? Quick interstellar or intergalactic travel is a closely related issue, but also of interest to science fiction writers. According to relativity, nothing move faster than light. Therefore, if we the nearest star to our α-Centauri - Send space ship, as it is about 4 light years away, so we expect at least 8 years to wait until the travelers to come back to report their findings. If you go explore the galaxy center, at least 10 years before returning. Relativity does give us some relief. A young lady were White, She can do it faster went fairly light. Her relative way, Just starting on the day, Already arrived in the night before. The key is that there is no theory of relativity all observers agree that the only time measurement. On the contrary, each have their own time measurement observer. If a rocket at less than the speed of light from the event A (such as the 2012 Olympic 100 meters final race) to the event B (such as α-Centauri Parliament's opening session, 100,004), then based on all observations by the time they all agreed the event A occurs in the event B of the first. However, assuming that the spacecraft must be more than the speed of light sent a message to the Competition Council, then the observers at different velocities on the event A and event B after what the former what is controversial. According to one observer at rest relative to Earth, perhaps the opening of Parliament after the contest. In this way, the observer would think that if he ignores the speed of light restriction, the spacecraft arrived in time from the A B. However, in the α-Centaur seat close to the speed of light flying in the direction of the observer to leave the Earth will feel the event B, that is, the opening of Parliament, before the event A, that is, place the final meters. Theory of relativity tells us. For observers at different velocities, the laws of physics are the same. This experiment has been well tested. It is believed that the use of more advanced theory to replace relativity, it will still be retained as a characteristics. Thus, if FTL travel is possible, movement of observers would say that it is possible from the event B, that is, the opening ceremony of Parliament, arrived at the event A, that is, meters race. If he is moving so quickly, he even had time before the event back, and in that case who is the winner put down stakes. There are some barriers to break the speed of light problem. Theory of relativity tells us that the speed of the spacecraft closer to the speed of light for its power to accelerate the rocket to be growing. We have experimental evidence for this, but not the space shuttle experience, but such as Fermilab or CERN particle accelerator in the experience of elementary particles. We can accelerate particles to 99.99% the speed of light, but no matter how much we are into power, nor can they accelerate beyond the speed of light barriers. Space shuttle situation was similar: no matter how high power rocket, and can not accelerate to the speed of light above. 】 【Wormhole Wormhole, also known as worm holes. It would appear that rapid space of time travel and travel seems to have the feasible. However, there may be ways. Perhaps people can curl up into space so that between A and B have a short cut. Between the A and B is a sure way to create a wormhole. As the name suggests, is a space-time wormhole thin tube, which can both nearly flat regions far apart connected. Wormhole-based time machine built three simple steps is not 1. To find or create a wormhole to open up a tunnel used to connect two different regions in space. Large wormholes might naturally in outer space, is the remnants of the Big Bang. If not true, then we had to make do with smaller than atoms wormhole, either natural products (around us, every moment has a small wormhole that birth and death), or man-made products ( shown on such place, they are produced by a particle accelerator). These smaller wormhole must be extended to a practical size, may have to use those in the lead shortly after the Big Bang space expansion of the energy field. 2. The wormhole stabilized. Into the use of so-called Casimir effect generated by the quantum of negative energy, the wormhole would allow the signals and objects safely through it. Negative energy density will resist for the wormhole collapse or near-infinite infinite point of the trend. In other words, it prevents the wormhole turned into a black hole. 3. Traction wormhole. A highly advanced technology spacecraft will separate from each other wormhole entrance. An entry may be placed in the neutron star surface, it is a strong gravitational field, extremely dense stars. Strong gravity makes time slow down. Another entrance to the wormhole as time goes by faster, the results of these two entrances, not only in space but in time have been divided leave. The leap to high-speed movement is a way of the future. Gravity is another means. In Einstein's general relativity, he predicted that gravity can slow the passage of time. Compared with in the basement, bell to go faster on some of the top floor, in the center of the earth and thus closer to more in-depth in the case of gravitational field, this phenomenon will become more significant. Similarly, the clock in space go faster than the ground. Although this effect is minimal, but it has been directly measured precise clock. Indeed, global positioning system must take into account the time bending effects. If they do not take this into account, sailors, taxi drivers and cruise missiles will find their own provisions deviate from the track there are many kilometers. Until now, I have discussed the future of travel in the time North Korea situation. So retrograde what will happen? This will happen far into the issue. 1948, Institute for Advanced Study Princeton, New Jersey's Kurt Gabriel Einstein gravitational field equation is proposed as a description of the solution of rotating universe. In this universe, an astronaut to travel in space to achieve the purpose of back. This is the result of gravitational influence of light. Lead to optical rotation of the universe (and therefore also the causal link between things) was grabbed and surrounded in its interior, which makes a kind in a closed loop can be closed in the space to move, but also in the closed loop in time travel, but not at any time over the speed of light relative to the adjacent particles. Gabriel's explanation is as mathematical adventures and shelved - after all, there is no evidence that the universe as a whole observed in the rotation. But his results show retrograde in time does not violate relativity. Indeed, Einstein said he worked his theory may in some cases allowed to return to the idea of the past confused. Allowed to return to the past a number of other suspect has been found. For example, in 1974, Tulane University, Frank J. Tipler, a huge computing infinitely long rotating cylinder, the axis of its place, the astronauts were able to visit close to the speed of light to their own past, that is, near the cylinder drag drag a ring of light. In 1991, Princeton University, J. Richard Gott predicted cosmic strings - cosmologists imagine its structure is produced in the early Big Bang - and can produce similar results. But the 20th century, the emergence of the mid-80s time machine the most realistic scenario is based on the concept of wormhole conceived. In science fiction, wormholes are sometimes called Star Gate; they provide a through space far away from each other, a shortcut between two points. Skip a hypothetical wormhole, you may appear in a moment later the other side of the galaxy. Wormhole naturally found general relativity, with gravity, not only can bend space, but also allow time distorted. Theory allows to connect two points in the optional space in the tunnel path and the existence of such a thing. Mathematicians proposed space in the form of multiple links. As the end of the tunnel through the mountain road surface than the shorter mountain, like a wormhole may also throughout the general space than the usual route to more short. Carl Sagan in his 1985 novel "Contact", in relation to use of the wormhole as a fictional device. In Sagan's suggestion, Kip S. Thorne and his colleagues at the California Institute of Technology _set_ out to study the physics of the wormhole is consistent with the known. Their starting point is the same wormhole as a black hole with terrible gravity of the object. But the difference is the black hole, which is not only a one-way travel destinations, and the wormhole will also have an outlet and an entrance. Is available through the wormhole, it must contain strange matter Thorne said. In fact, this is some kind of anti-gravity effect can produce a large-scale system to resist the powerful gravity of its own that was pressed into the natural tendency of the material the black hole. Anti-gravity, or other than the repulsion from the negative to produce energy or negative pressure. As we all know, the negative energy state exists in a particular quantum system, it is not that Thorne's exotic matter is forbidden by the laws of physics, although it is not clear whether collected enough material against gravity in order to stabilize a wormhole. Thorne and his colleagues soon recognized that if a stable wormhole can be created, it can easily turn into a time machine. Perhaps one of the astronauts through the wormhole can not only occur somewhere in the universe, but also in a certain period, that is - in the future or the past. To make a wormhole for time travel, it is a hole which leads to a neutron star should be there, and placed close to the neutron star surface areas. Stellar gravity will slow the passage of time near the wormhole openings, which makes the time difference between the two ends of the wormhole gradually accumulated. If two ports are placed in the right place in space, then the time difference will remain frozen. Assuming that this difference is 10 years. An astronaut from one direction through the wormhole, he will jump to 10 years in the future, on the contrary, if the astronauts through the wormhole from another direction, he will jump past 10 years. The second astronaut in space at high speed through the usual back to the starting point, he might be coming home before departure. In other words, the closed loop space might turn into a time in the ring. One limitation is the first time, astronauts can not go back to the period before the establishment of a wormhole. A terrible challenge is the initial creation of the wormhole would hamper the manufacture of a wormhole-based time machine. Perhaps such a class structure of space from the string of natural fused - remnants of the Big Bang. If this is the case, a super-civilization would be able to use a wormhole. Perhaps the wormhole is in a very small scale (the so-called Planck length, about 10-20 nuclear scale is so small) naturally occurring. In principle, such a tiny pulse of energy may be to stabilize the wormhole, and then expanded in some way to can take advantage of size. If the many engineering challenges have been overcome, time machine production will open Pandora's Box causal paradox. For example, a time traveler to visit the past, the murder of a young girl's mother. How do we understand these things mean? If this girl died, she can not be time traveler's mother. But if it were time travelers never had, he would not return to the past and the murder of his mother. The mother of the famous paradox (sometimes with other family relationship to systematic exposition) is due to people or objects can reverse time and change the past caused. Pinball is a simplified version of the case. A marble through a wormhole-based time machine, then it will hit at the time of its own earlier, thereby preventing it from ever entering the wormhole. Paradox solutions from a simple understanding: marbles can not go against logic or act in violation of the laws of physics. It certainly can not stop going through the wormhole in their own way, but nothing will stop an infinite number of marbles in other ways through the wormhole. Quantum Physics】 【 Space-time wormhole between different regions is not science fiction writers thought the invention, its origin is very respectable. Energy a bit like money: if you have positive energy, you can use different methods of distribution, but based on the classic beginning of this century that law, you do not allow overdrafts. Thus, these classical laws exclude any possibility of time travel. However, quantum laws have gone beyond the classical law. Uncertainty principle of quantum laws are based. Some of the quantum laws of more generous, as long as you total energy is positive, you will allow from one or two accounts overdrawn. In other words, quantum theory allows the energy density in some places is negative, as long as it is in other places by the energy density of the compensation, so the total energy remains positive. Quantum theory allows negative energy density is an example of the so-called Casimir effect, and we even considered "empty" space is filled with virtual particles and virtual anti-particles, which appear together in minutes and then back together and annihilate each other. Now, assume that people have two very close parallel metal plates. Metal mirrors for the virtual photon plays a similar role. In fact, in a cavity formed between them. It is a bit like organ pipes, only specify the scale of the resonance. This means that only when the plate is the distance between the virtual photon wavelength (the distance between adjacent peaks) of an integer multiple of, these virtual photons into space will appear in the flat. If the cavity width is a multiple of the wavelength of the fact that some wavelengths, then reflected many times before and after the crest of a wave trough will coincide with another, this was off_set_ fluctuations. Because the plate can have a virtual photon between the resonant wavelength, so the number of virtual photons outside the region than in the flat slightly less, than in the flat virtual photon can have any wavelength. So people can expect to suffer the two pieces flat force them to squeeze inside. This force actually measured. And and the predicted values. In this way, we get the existence of virtual particles and has the effect of the experimental evidence is. In the flat there are fewer virtual photons between the fact that the energy density means that they are much smaller than it is at. But away from the flat of the "empty" space, the total energy density must be zero, because otherwise, the energy density of space would curl up, but can not remain nearly flat. Thus, if the plate than the distance between the energy density of the energy density is smaller, it must be negative. However, the alien or any person from the future visits should be more obvious, perhaps even more unpleasant. If they are apparitions, why only those who are considered less reliable witnesses? If they try to warn us of imminent disaster, this is not very effective. A kind of visitor from the future possible explanation is the absence, as we observed in the past and found that it was not allowed to travel back from the future, the kind needed to curl, so the past is fixed. On the other hand, the future is unknown open, so it may be necessary curvature. This means that any time travel had been limited to the future. At this moment, Captain Kirk and the interstellar ship not have a chance. 】 【Contradiction This may explain why the world is not full of tourists from the future. But if people can go back and change history, the problem can not be avoided. For example, suppose you go back to the past and your ancestors killed when he was still a child. There are many versions of these paradoxes, but they basically are equivalent: if a person is free to change the past, he will encounter conflict. It seems there are two ways to solve the paradox caused by time travel. Historical method, called coordination. It is about, even when space is curled too may travel to the past, what happened in space and time must be the solution of the coordination of the laws of physics. According to this view, unless the history suggests that you have arrived in the past, and did not kill your ancestors or any act not in conflict with your current situation, you can return to the past. Moreover, when you return to the past, you can not change the historical record. That means that you are not free will do whatever they want. Of course, one could say that free will is illusory anyway. Constraints if there is indeed a complete unified theory of all things, it should determine your actions. But for such a complex organism like humans, their constraints and decisions can not be calculated way. We say that people have the will, is that we can not predict their future actions. However, if a person off of travel by rocket and spacecraft have returned before this, we will be able to predict their future behavior, because that would be part of recorded history. Thus, in this case, the time traveler time travel is not free will to solve the other possible scenario is known as the choice of history. The idea is that when the time travelers back to the past, he entered the historical record and the history of different to the other. In this way, they are free to act and not consistent with the history of the original constraints. Stephen Parker • Spiro very favorite movie, "Return to the Future" idea: Mati • Mark Frye and his parents to return to historical change more satisfying love. Feynman sum over histories allows the micro-scale travel to the past. Joint symmetry in the laws of science is invariant under CPT. This suggests that an anti-clockwise spin and movement from A to B, anti-particles can also be considered to be in the direction of the spin the clock back to A from B the usual particle movement. Similarly, a forward movement in time is equivalent to the usual particle movement in the next time the anti-particles. "Empty" space is filled with virtual particles and anti-particles, they appear together, separation, and then return to a mutual annihilation. That way, people can put on the particle that is in space and time along a closed movement of individual particles in Fig. When the pair in the forward movement in time (starting from the event it appears to reach its annihilation of the event), it is called Particles. However, when the particle movement back in time (starting from the arrival of the annihilation of the incident it appears the incident), anti-particles can be said to forward movement in time. In explaining why black holes emit particles and radiation that the virtual particle / anti-particle of a member (such as anti-particles) will fall into the black hole to the other members of the stay, lose and its annihilation partner. The particles can also be discarded into the black hole, but it can also break free from a nearby black hole. If so, for a distant observer, it as a particles emitted from black holes appear. However, the mechanism of black hole radiation, people can have different but is equivalent to the image. People can put that into the virtual black hole of the members (such as anti-particles) as the time from the black hole in the back out of the particle motion. When it reaches the virtual particle-antiparticle pair appeared together with the point, it is scattered into the gravitational field to escape from a black hole in the forward movement in time of particles. Conversely, if the members of virtual pair of particles falling into the black hole, one could think it out from the black hole back in time in the movement of anti-particles. This shows that the black hole radiation, quantum theory at the micro scale to allow back in time in the campaign, and this time travel can produce observable effects. The resulting question: quantum theory at the macro scale can be used to allow people time to travel? At first glance should be possible. Feynman's vision of history is the sum of all the history of the. Thus, it should include is curled to allow space travel to the past. Why, then, we have not harassed by history? For example, suppose some people back, and to provide atomic secrets to the Nazis? If the defense called the timing conjecture, these problems will be avoided. It is speaking, the laws of physics prevent the macroscopic objects to pass information to the past. It is the same as the universe supervision guess, is not proven, but the reason to believe that it is established. When the time travelers try to change the past, such was not the paradox appears. But that does not prevent a person to become part of the past. Assume that the time travelers back in time to save from the murder of a young girl, the girl grew up to be his mother. So now is the self-consistent causal link, and no paradox. Causal consistency might impose restrictions on the time traveler can do things, but this does not rule out time travel itself. Time travel bizarre reasoning led some scientists reject the idea completely. Cambridge University's Stephen Hawking proposed a "chronology protection conjecture", which will announce the failure of the causal loop. As we all know, the theory of relativity to allow causal loop exists, a chronology protection is necessary to introduce other factors to mediate, to prevent travel to the past to happen. This factor may be what is it? One proposal is to solve the problem of quantum process. Time Machine will allow the existence of particles circulating into their past. The results suggest a disturbance will occur immediately self-enhancement, resulting from the surge of energy to escape can cause wormhole collapse. Chronology protection is still nothing but a guess, it still retained the possibility of time travel. A final solution to resolve the matter of quantum mechanics and gravity must be looking forward to the successful combination, perhaps with the expansion of string theory or its theory that the so-called M-theory. We even can imagine the next generation of particle accelerators will be able to generate atomic-scale Shakespeare wormhole, they can exist long enough to make the vicinity of the implementation of fleeting particles can cause ring. This time machine to Biweiersi imagination for much more far-reaching, it will forever change our picture of physical reality. About time travel, still remain in the guess stage, no substantial progress, the limited space here does not expand the discussion, see: space shuttle, minutes feet slowly shrinking, science, time tunnel, time back, four-dimensional space
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English Expression
: Time Travel
Related Phrases
science
relativism
science fiction
hour belt
universe
liuwenyang
science fiction World
Containing Phrases
Time travel law
elapse excursionist
elapse excursionist countess
Layton Professor and Final Time Travel
Layton Professor And Final Time Travel
affiliate Time travel of In great demand issue
General relativity theory AND Time Travel
regarding Time travel of Divers in great demand issue