Time Travel Essay Example for Free

Time Travel Essay The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many. While the idea makes for great fiction, some scientists now say traveling to the past is impossible. There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller, â€Å"The Elegant Universe† and a physicist at Columbia University. â€Å"And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it. Most of us think that almost all of them can be ruled out. † The fourth dimension In physics, time is described as a dimension much like length, width, and height. When you travel from your house to the grocery store, you’re traveling through a direction in space, making headway in all the spatial dimensions—length, width and height. But you’re also traveling forward in time, the fourth dimension. â€Å"Space and time are tangled together in a sort of a four-dimensional fabric called space-time,† said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book â€Å"One Universe: At Home In The Cosmos. † Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions. â€Å"When something that has mass—you and I, an object, a planet, or any star—sits in that piece of four-dimensional spandex, it causes it to create a dimple,† he said. â€Å"That dimple is a manifestation of space-time bending to accommodate this mass. † The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity. Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom. â€Å"In this four-dimensional space-time, you’re only able to move forward in time,† Liu told LiveScience. * Video: Can You Time Travel? Tunneling to the past A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole—a hypothetical tunnel connecting two regions of space-time. The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side. â€Å"Wormholes are the future, wormholes are the past,† said Michio Kaku, author of â€Å"Hyperspace† and â€Å"Parallel Worlds† and a physicist at the City University of New York. â€Å"But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today’s technology. † To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing. Greene, an expert on string theory—which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and natures fundamental forces, questioned this scenario. â€Å"Many people who study the subject doubt that that approach has any chance of working,† Greene said in an interview . â€Å"But the basic idea if you’re very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time. † Cosmic strings Another popular theory for potential time travelers involves something called cosmic strings—narrow tubes of energy stretched across the entire length of the ever-expanding universe. These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them. Cosmic strings are either infinite or they’re in loops, with no ends, said J. Richard Gott, author of â€Å"Time Travel in Einsteins Universe† and an astrophysicist at Princeton University. â€Å"So they are either like spaghetti or SpaghettiO’s. † The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory. â€Å"This is a project that a super civilization might attempt,† Gott told LiveScience. â€Å"It’s far beyond what we can do. We’re a civilization that’s not even controlling the energy resources of our planet. † Impossible, for now Mathematically, you can certainly say something is traveling to the past, Liu said. â€Å"But it is not possible for you and me to travel backward in time,† he said. | However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical. Maybe if there were a theory of everything, one could solve all of Einstein’s equations through a wormhole, and see whether time travel is really possible, Kaku said. â€Å"But that would require a technology far more advanced than anything we can muster, he said. Don’t expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement. † For now, the only definitive part of travel in the fourth dimension is that we’re stepping further into the future with each passing moment. So for those hoping to see Earth a million years from now, scientists have good news. â€Å"If you want to know what the Earth is like one million years from now, I’ll tell you how to do that,† said Greene, a consultant for â€Å"Deja Vu,† a recent movie that dealt with time travel. â€Å"Build a spaceship. Go near the speed of light for a length of time—that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth’s future. † Source 2 Time Slips / Time Travel 0digg 1 comment A time slip is an alleged paranormal phenomenon in which a person, or group of people, travel through time through supernatural (rather than technological) means. As with all paranormal phenomena, the objective reality of such experiences is disputed. One of the best-known, and earliest, examples of a time slip was reported by two English women, Charlotte Anne Moberly (16 September 1846 – 7 May 1937) and Eleanor Jourdain (1863–1924), the principal and vice-principal of St Hugh’s College, Oxford, who believed they slipped back in time in the gardens of the Petit Trianon at Versailles from the summer of 1901 to the period of the French Revolution. On August 10, 1901 Moberly and Jourdain were visiting the Palace of Versailles. They decided to go in search of the Petit Trianon. While walking through the grounds they both were impressed by a feeling of oppressive gloom. They claimed to have encountered, and interacted with, a number of people in old fashioned attire whom they later assumed to have been members of the court of Marie Antoinette and to have seen a figure that may have been Marie Antoinette herself on the day in 1792 when she learned that the mob had stormed the Tuileries Palace. Source 3, 4, 5 . http://www. youtube. com/watch? feature=player_embeddedv=FdWXMD4rOGQ#! http://www. youtube. com/watch? feature=player_embeddedv=rqQV_UzVQks http://www. youtube. com/watch? v=X02WMNoHSm8 Source 6 The Big Question: Is time travel possible, and is there any chance that it will ever take place? By Steve Connor, Science Editor Friday 08 February 2008 Why are we asking this now? Two Russian mathematicians have suggested that the giant atom-smasher being built at the European centre for nuclear research, Cern, near Geneva, could create the conditions where it might be possible to travel backwards or forwards in time. In essence, Irina Arefeva and Igor Volovich believe that the Large Hadron Collider at Cern, which is due to be switched on this year for the first time, might create tiny wormholes in space which could allow some form of limited time travel. If true, this would mark the first time in human history that a time machine has been created. If travelling back in time is possible at all, it should in theory be only possible to travel back to the point when the first time machine was created and so this would mean that time travellers from the future would be able to visit us. As an article in this weeks New Scientist suggests, this year – 2008 – could become year zero for time travel. Is this really a serious proposition? The New Scientist article points out that there are many practical problems and theoretical paradoxes to time travel. Nevertheless, the slim possibility remains that we will see visitors from the future in the next year, says the magazine says, rather provocatively. It has to be said that few scientists accept the idea that the Large Hadron Collider (LHC) will create the conditions thought to be necessary for time travel. The LHC is designed to probe the mysterious forces that exist at the level of sub-atomic particles, and as such will answer many important questions, such as the true nature of gravity. It is not designed as a time machine. In any case, if the LHC became a time machine by accident, the device would exist only at the sub-atomic level so we are not talking about a machine like Dr Whos Tardis, which is able to carry people forwards and backwards from the future. What do the experts say about the idea of time travel? The theoretical possibility is widely debated, but everyone agrees that the practical problems are so immense that it is, in all likelihood, never going to happen. Brian Cox, a Cern researcher at the University of Manchester, points out that even if the laws of physics do not prohibit time travel, that doesnt mean to say its going to happen, certainly in terms of travelling back in time. Saying that the laws of physics as we know them permit travel into the past is the same as saying that, to paraphrase Bertrand Russell, they permit a teapot to be in orbit around Venus, Dr Cox says. Its possible, but not likely. Time travel into the future is absolutely possible, in fact time passes at a different rate in orbit than it does on the ground, and this has to be taken into consideration in order for satellite navigation systems to work. But time travel into the past, although technically allowed in Einsteins theory, will in the opinion of most physicists be ruled out when, and if, we develop a better understanding of the fundamental laws of physics – and thats what the LHC is all about. Why is the possibility of time travel even considered? It comes down to the general theory of relativity devised by Albert Einstein in 1905. It is the best theory we have so far on the nature of space and time and it was Einstein who first formulated the mathematical equations that related both time and space in the form of an entity called space-time. Those equations and the theory itself do not prohibit the idea of time travel, although there have been many attempts since Einstein to prove that travelling back in time is impossible. Is there anything to support the theory? Lots of science fiction writers have had fun with time travel, going back to H. G. Wells, whose book The Time Machine was published in 1895 – 10 years before Einsteins general theory of relativity. Interestingly, it was another attempt at science fiction that revived the modern interest in time travel. When Carl Sagan, the American astronomer, was writing his 1986 novel Contact, he wanted a semi-plausible way of getting round the problem of not being able to travel faster than the speed of light – which would break a fundamental rule of physics. He needed his characters to travel through vast distances in space, so he asked his cosmologist friend Kip Thorne to come up with a possible way of doing it without travelling faster than light. Thorne suggested that by manipulating black holes it might be possible to create a wormhole through space-time that would allow someone to travel from one part of the Universe to another in an instant. He later realised that this could also in theory be used to travel back in time. It was just a theory of course, and no one has come close to solving the practical problem of manipulating black holes and creating wormholes, but the idea seemed to be sound. It spawned a lot of subsequent interest in wormholes and time travel, hence the latest idea by the two Russian mathematicians. Apart from the practicalities, whats to stop time travel? The biggest theoretical problem is known as the time-travel paradox. If someone travels back in time and does something to prevent their own existence, then how can time travel be possible? The classic example is the time traveller who kills his grandfather before his own father is conceived. Cosmologists, renowned for their imaginative ingenuity, have come up with a way round this paradox. They have suggested that there is not one universe but many – so many that every possible outcome of any event actually takes place. In this multiple universe, or multiverse model, a woman who goes back in time to murder her own granny can get way with it because in the universe next door the granny lives to have the daughter who becomes the murderers mother. Where does this leave the time machine in Geneva? The science writer and physicist John Gribbin, who explains these things better than most, points to a saying in physics: anything that is not forbidden is compulsory. So they expect time machines to exist. The snag is that the kind of accidental time tunnel that could be produced by the LHC in Geneva would be a tiny wormhole far smaller than an atom, so nothing would be able to go through it. So there wont be any visitors from the future turning up in Geneva just yet. Id take it all with a pinch of salt, but it certainly isnt completely crazy. So, not completely crazy, just a bit crazy. So will we one day be able to travel into the future? Yes * There is nothing in the laws of physics to prohibit it, and events in Geneva are pointing the way and could be a first step * In physics, so the saying goes, if nothing is prohibited, it must happen at some point * All we need to do is to work out how to manipulate black holes and wormholes, and away we go No * The practical problems with time travel are too immense to solve, and even if you could, who would want to? * You might travel back in time and kill one of your grandparents by accident. Then where would you be? * If time travel is possible, why are we still waiting to welcome our first visitors from the future? Source 7 Time Travelers By Stephen Wagner, About. com Guide Where and to what date would you go if you could travel through time? Its a question people have long enjoyed contemplating the possibilities are so fraught with wonder and excitement. Would you watch the pyramids of Egypt being build? Join the spectacle of a gladiatorial battle at the Roman Coliseum? Catch a glimpse of real dinosaurs? Or would you prefer to see what the future holds for humankind? Such fantasies have fueled the success of such stories as H. G. Welles The Time Machine, the Back to the Future movies, favorite episodes of Star Trek and countless science fiction novels. And although some scientists think that it might be at least theoretically possible to travel through time, no one (as far as we know) has devised a sure-fire way to make it happen. But thats not to say that people havent reported traveling through time. There are many fascinating anecdotes from those who say they seem to have quite unexpectedly visited if only briefly another time and, sometimes, another place. These events, often called time slippages, seem to occur randomly and spontaneously. Those who experience these events are often bewildered and confused by what they see and hear, and afterward are at a complete loss to explain them. Here are some interesting cases that will keep you wondering: FLIGHT INTO THE FUTURE In 1935, Air Marshal Sir Victor Goddard of the British Royal Air Force had a harrowing experience in his Hawker Hart biplane. Goddard was a Wing Commander at the time and while on a flight from Edinburgh, Scotland to his home base in Andover, England, he decided to fly over an abandoned airfield at Drem, not far from Edinburgh. The useless airfield was overgrown with foliage, the hangars were falling apart and cows grazed where planes were once parked. Goddard then continued his flight to Andover, but encountered a bizarre storm. In the high winds of the storms strange brown-yellow clouds, he lost control of his plane, which began to spiral toward the ground. Narrowly averting a crash, Goddard found that his plane was heading back toward Drem. As he approached the old airfield, the storm suddenly vanished and Goddards plane was now flying in brilliant sunshine. This time, as he flew over the Drem airfield, it looked completely different. The hangars looked like new. There were four airplanes on the ground: three were familiar biplanes, but painted in an unfamiliar yellow; the fourth was a monoplane, which the RAF had none of in 1935. The mechanics were dressed in blue overalls, which Goddard thought odd since all RAF mechanics dressed in brown overalls. Strange, too, that none of the mechanics seemed to notice him fly over. Leaving the area, he again encountered the storm, but managed to make his way back to Andover. It wasnt until 1939 that that the RAF began to paint their planes yellow, enlisted a monoplane of the type that Goddard saw, and the mechanics uniforms were switched to blue. Had Goddard somehow flown four years into the future, then returned to his own time? CAUGHT IN A TEMPORAL VORTEX Dr. Raul Rios Centeno, a medical doctor and an investigator of the paranormal, recounted to author Scott Corrales a story told to him by one of his patients, a 30-year-old woman, who came to him with a serious case of hemiplegia the total paralysis of one side of her body. I was at a campground in the vicinity of Markahuasi, she told him. Markahuasi is the famous stone forest located about 35 miles east of Lima, Peru. I went out exploring late at night with some friends. Oddly enough, we heard the strains of music and noticed a small torch-lit stone cabin. I was able to see people dancing inside, but upon getting closer I felt a sudden sensation of cold which I paid little attention to, and I stuck my head through an open door. It was then that I saw the occupants were clad in 17th century fashion. I tried to enter the room, but one of my girlfriends pulled me out. It was at that moment that half of the womans body became paralyzed. Was it because the womans friend pulled her out of the stone cabin when she was half entered into it? Was half her body caught in some temporal vortex or dimensional doorway? Dr. Centeno reported that an EEG was able to show that the left hemisphere of the brain did not show signs of normal functioning, as well as an abnormal amount of electric waves. (See Dimensions Beyond Our Own for more details on this story. ) Source 8 How Time Travel Works by Kevin Bonsor and Robert Lamb Stuff You Should Know From millennium-skipping Victorians to phone booth-hopping teenagers, the term time travel often summons our most fantastic visions of what it means to move through the fourth dimension. But of course you dont need a time machine or a fancy wormhole to jaunt through the years. As youve probably noticed, were all constantly engaged in the act of time travel. At its most basic level, time is the rate of change in the universe and like it or not, we are constantly undergoing change. We age, the planets move around the sun, and things fall apart. We measure the passage of time in seconds, minutes, hours and years, but this doesnt mean time flows at a constant rate. Just as the water in a river rushes or slows depending on the size of the channel, time flows at different rates in different places. In other words, time is relative. But what causes this fluctuation along our one-way trek from the cradle to the grave? It all comes down to the relationship between time and space. Human beings frolic about in the three spatial dimensions of length, width and depth. Time joins the party as that most crucial fourth dimension. Time cant exist without space, and space cant exist without time. The two exist as one: the space-time continuum. Any event that occurs in the universe has to involve both space and time. In this article, well look at the real-life, everyday methods of time travel in our universe, as well as some of the more far-fetched methods of dancing through the fourth dimension. Source 9 Is Time Travel Possible? Analysis by Robert Lamb Thu Apr 22, 2010 06:14 PM ET Its not glamorous, but its time travel. (Michael Dunning/Photographers Choice/Getty Images) From summer blockbusters to sensational science headlines, modern culture is constantly inundated with tales of time travel. But when you boil down the physics involved, is it possible to travel through time? To answer this question, I tracked down theoretical physicist and cosmologist Paul Davies, author of How to Build a Time Machine. SLIDE SHOW: What are the favored time travel methods as used in science fiction? We are all time travelers The short answer is that time travel into the future is not only possible, its been done, and weve known about it for over a century, says Davies. The reason that the public doesn’t seem to know about it is because the amount of time travel involved is so pitifully small that it doesnt make for a Doctor Who style adventure. A phenomenon called time dilation is the key here. Time passes more slowly the closer you approach the speed of light an unbreakable cosmic speed limit. As such, the hands of a clock in a speeding train would move more slowly than those in a stationary clock. The difference would not be humanly noticeable, but when the train pulled back into the station, the two clocks would be off by billionths of a second. If such a train could attain 99. 999 percent light speed, only 1 year would pass onboard for every 223 years back at the train station. But speed isnt the only factor that affects time. On a much smaller scale, mass also influences time. Time slows down the closer you are to the center of a massive object. Time runs a little bit faster in space than it does down on Earth, Davies says. It runs a little faster on the roof than it does in the basement, and thats a measurable effect. A clock aboard an orbiting satellite experiences time dilation due to both the speed of its orbit and its greater distance from the center of Earths gravity. Both gravity and speed can give you a means of jumping ahead, Davies says. So in principle, if you had enough money, you could get to the year 3000 in as short a time as you like one year, one month, whatever it takes. It is only a question of money and engineering. Forward, not back? Time travel into the future is an established and fundamental aspect of Albert Einsteins theory of relativity. Scientists have tested and retested this in both experimental and practical settings. But what about time travel in the opposite direction? Going back in to the past is a whole different kettle of fish. Davies says. Theres nothing in Einsteins theory, which is the best theory that we have about the nature of time, which precludes it. Theres nothing in even his general theory of relativity, published in 1915, which precludes travel back into the past, but many scientists are deeply uneasy about it because of all the well-known paradoxes that it unleashes. For instance, imagine going back in time and killing your own mother. Then shed never give birth to you, and just how would you have been able to travel back in time to commit matricide in the first place? Wormholes as spacetime shortcuts Davies surmises that, given our current understanding of the nature of time and physics, time travel into the past simply isnt possible. But the universe is full of mysteries, and one of them the hypothetical wormhole might just permit such a journey. This is a little bit like a tunnel or shortcut between two distant points, Davies says, So for example, if I had a wormhole here in my hotel room and I jumped through it I wouldnt come out on Pennsylvania Avenue, Id maybe come out near the other side of the galaxy. Source 10 Scientists have theorized that such a shortcut through time and space could be turned into a time machine. If a worm hole could exist and could be traversable, then it would provide a means of going back in time, Davies says. So it all hinges on whether stable wormholes are a reality or if theres some aspect of physics not relativity, because theres nothing wrong from that point of view but some other aspect of physics might intercede and prevent the wormhole from forming. Thats an open question. World-famous theoretical physicist Stephen Hawking has proposed that wormholes occurring at a quantum level could theoretically provide a foothold for time travel, but University of California at Santa Barbara physicist Andrew Cleland urges caution on that front. Im an experimentalist, and physics is ultimately an experimental science, Cleland says. Any predictions that are made based on mathematics or on philosophical or intellectual speculation have to pass the test of experiment, and I am certainly not aware of any experiment that demonstrated the possibility of traveling backward in time. Cause and effect Cleland also points out that the fundamental principle of causality stands in the way of travel into the past. The entire universe, as we understand it, is beholden to this rule. Something occurs first and the outcome of that occurrence happens afterward, Cleland says, and there has never to my knowledge been an experiment that came out different from that. I am not aware of any experimental tests of quantum mechanics that have shown any violation of causality, in spite of the fact that many experiments could reveal such a violation. Still, in the same way that time dilation isnt flashy enough to seem like time travel into the future, the public often overlooks a very common means of traveling into the past. In a sense, astronomers are always traveling backward in time, but it is in a way that most people are not so excited about, Cleland says. When we measure the cosmic microwave background, were looking back more than 10 billion years in time. Thats how long it took for the light to reach us. A number of questions about time travel remain unanswered. Will time tourists from the future ever show up to help us out? Well just have to wait and see. But if they come here using a wormhole time machine, well have to build one first. After all, you couldnt cross a bridge if only one side had been completed, right? Theoretically, it would take more than 100 years to create a 100-years time difference between the two ends of a wormhole, Davies says, so theres no way that our descendants could come back and tell us were wrong about this.